Guy Holt

I personally believe that in night scenes you should always combine color temperatures in the frame. You can shift your overall color balance to the cool side to create moonlight, but without a white light or warm light reference in the frame, your audience will subconsciously adjust and filter out your moonlight effect. Putting white light in the frame gives your audience a reference point and a color effect like moonlight stands out in contrast to it . It doesn't need to be much - just a dim light in the room behind your father or a streak of light across the foreground as if coming from another room. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip equipment sales and rentals in Boston.

The Honda EU65 is not crystal governed – it doesn’t have to be. Crystal engine governors are required in conventional AVR generators to eliminate flicker with magnetic HMI ballasts because the frequency of the AC power they generate is a function of the engine speed. Inverter generators like the EU65 break the link between engine rpm and Hz by taking the raw power produced by the alternator and passes it through a microprocessor controlled multi-step process to condition it. But, rather than using simple two pole cores, the alternators of inverter generators use multi-pole cores and small stators to produce a raw AC power that is multiphase (more than 300 overlapping sine waves), high frequency (up to 20’000 Hz), and upwards of 200 Volts. This high voltage AC power is then converted to DC. Finally the DC power is converted back to low voltage single phase AC power by the inverter. In the process the inverter cleans and stabilizes the power. The end result is AC power that is nearly a pure sine wave with a wave distortion of only 2.5% (which is as clean or cleaner than commercial power), a voltage stability within ± 1%, and frequency stability within ± 0.01 HZ. With power that stable, a crystal governor is simply not needed to eliminate flicker. Actually the opposite is true. If you don’t have access to the newest Power Factor Corrected (PFC) electronic ballasts, you are better served by using the older magnetic ballasts on an inverter generator (like the Honda EU6500is) over non-PFC electronic ballasts on conventional AVR generators (like the Honda EX5500 or ES6500) with crystal governors. Where this is contrary to the conventional wisdom, allow me to explain some of the advantages to operating magnetic ballasts on inverter generators. With a frequency variance of only hundredths of a cycle, magnetic ballasts will operate “flicker free” on inverter generators, without the need for costly crystal governors, as long as you shoot at one of the many safe frame rates. Besides the extra bulk and weight of magnetic ballasts, the smaller magnetic ballasts (575-2500W) offer the distinct advantage of being less expensive and drawing less power (13.5A versus 19A for a 1.2kw) once they have come up to speed than the commonly available non-PFC electronic equivalents. Finally, magnetic ballasts will operate more reliably on inverter generators, than non-PFC electronic ballasts operate on AVR generators. The reason being the leading power factor caused by the capacitive reactance of non-PFC electronic ballasts have a more severe effect on the power waveform of conventional AVR generators than do magnetic ballasts on the power waveform of inverter generators. Of course there are downsides to using magnetic ballasts. One down side is that you are restricted to using only the safe frame rates and shutter angles. But, when you consider that every film made up to the early 1990s were made with magnetic HMI ballasts you can see that being limited to the safe frame rates is not all that restrictive. Another downside to magnetic ballasts is that you can’t load the generator to full capacity because you must leave “head room” for their higher front end striking load. When choosing HMIs to run off portable generators, bear in mind that magnetic ballasts draw more current during the striking phase and then they “settle down” and require less power to maintain the HMI Arc. By contrast, an electronic ballasts “ramps up.” That is, its’ current draw gradually builds until it “tops off.” For more details on how to operate magnetic HMI ballasts on portable gas generators see an article I wrote for our company newsletter called “Portable Generators in Motion Picture Production”. Guy Holt, Gaffer, ScreenLight & Grip

DIY is not only for low budget indies. As Klas points out, similar rigs are used all the time on big budget features. The one’s I’ve worked with have had chicken wire arched over the bulbs so that you can had diffusion or gel quickly. When it comes to lighting equipment, you generally get what you pay for. Lighting gear is so specific to the requirements of our industry that it is hard to build your own. Take fluorescent lights. Kinos use high frequency ballasts to eliminate flicker or scrolling. You can get cheap high frequency fluorescent ballasts from a residential lighting supplier but they can have another type of flicker problem called an “eratz ripple.” Even though the ballasts put out a high-frequency cycle, that cycle stacks to create a lower frequency waveform which causes the light to pulsate. In a number of incidents, 24p video cameras and film cameras operating within a flicker-free window have picked up flicker from the “eratz ripple” effect. When making your own fluorescent soft banks it is necessary to shoot tests with the ballast you plan to use to make sure you will not get an “eratz ripple.” 
Kino Flo fixtures, on the other hand, use high frequency electronic ballasts that run at specific high frequencies that eliminate the generation of an “eratz ripple” (most at 25 kHz , the Parabeam Light at greater than 30 kHz) resulting in flicker free operation at any frame rate or shutter setting. Kino Flo ballasts also incorporate advanced electronic circuitry so that they will ignite a lamp instantly, even when cold, requiring no warm up time. To drive their tubes as brightly as possible, Kino Flo ballasts also send a higher output current to the lamps, than standard high frequency electronic fluorescent ballasts. For this reason only Kino Flo True Match lamps should be used in Kino Flo fixtures. The phosphors in Kino Flo True Match Lamps have been reformulated to match the spectral sensitivity curves of film and digital imaging equipment at the higher milliamps at which the ballasts operate. If that weren’t enough to justify the price of Kino fixtures, the newer Kino Flo fixtures that use the biax tubes use ballasts that include Power Factor Correction (PFC) circuitry. As it does in HMI ballasts, this advanced electronics contributes to a more economical use of power than conventional electronic ballasts. For example, a Kino Flo Parabeam 400 draws less than half of the power (2 Amps) of a comparable 4’ – 4 Bank “shop light” (4.6 Amps). While this nearly 3 amp difference is not a major consideration when using house power, it can make a difference when your power is coming from a portable generator because you can use two Parabeam 400s for the same power as a 4’ – 4 Bank “shop light”. With a Power Factor Rating of over .9, the Parabeam 400 fixtures are especially well suited for use on small portable generators. The fourth and final magical ingredient to Kino Flo ballasts pertains to the newer Biax fixtures (Diva, Parabeam, Vistabeam, Barfly) and is probably the most difficult to understand because it has to do with the vagaries associated with the load put on portable generators. If you haven't already, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting. In it I cover some of the basic electrical engineering principles behind harmonic distortion and how it can adversely effect generators. The article is available on our website. All fluorescent fixtures are a good choice for operation on small portable generators in the limited sense that they use a quarter of the power of a comparable tungsten soft light. However, the ballasts of conventional “shop lights” (as well as the older style Kino fixtures) that use the T-12 tubes are not Power Factor Corrected (PFC) and return harmonic currents into the power stream. When used in quantity, they can constitute a source of considerable harmonic noise. For this reason, on their website Kino Flo cautions users of their older style fixtures that also use T-12 tubes, that the ballasts “will draw double the current on the neutral from what is being drawn on the two hot legs. On large installations it may be necessary to double your neutral run so as not to exceed your cable capacity.”(FAQ “Why is the neutral drawing more than the hot leg”.) For a detailed explanation for why harmonic currents cause unusually high neutral returns see my article on the use of portable generators in motion picture production available on our website. Put simply, when you plug a single 4’ - 4 tube “shop light” into a wall outlet you need not be concerned about harmonic currents. As is the case with non-PFC HMI ballasts the impedance of the electrical path from the power plant is so low, the distortion of the original voltage waveform so small (1-3%), and the plant capacity so large in comparison to the load of the one light, that the inherently noisy load of the “shop light” will not affect the voltage at the distribution bus. Left: Grid Power w/ no load and a THD of less then 3%. Center: Conventional Generator w/ no load and a THD of 17-19%. Right: Inverter Generator w/ no load and a THD of 2.5%. It is, however, an all together different situation when plugging T-12 “shop light” fixtures into conventional portable generators. As a comparison of the oscilloscope shots above and below indicate, the return of harmonic currents by conventional T-12 ballasts can generate voltage distortion in the power stream. Given the large sub-transient impedance of conventional portable generators, and the fact that the original supply voltage waveform of conventional generators is appreciably distorted (a THD of 17-19%) to begin with , you have a situation where the return of any harmonic currents by a non-PFC electronic ballast (HMI or Kino) will result in significant waveform distortion of the voltage in the distribution system. Left: Grid Power w/ Kino Flo Wall-o-Lite. Center: Conventional AVR Power w/ Kino Flo Wall-o-Lite. Right: Inverter Power w/ Kino Flo Wall-o-Lite. Given the adverse effect of just a few conventional electronic fluorescent ballasts on a 5500W conventional generator, what is the accumulative effect of a typical lighting load made up of only non-PFC HMI & Fluorescent fixtures? To see, I ran a package consisting of two Arri 1200 HMI Par Pluses (with standard Arri non-PFC electronic ballasts) in addition to a 4’ – 10 tube Kino Flo Wall-o-Lite (with T-12 Ballasts) on a Honda EX5500 (a conventional generator). And, for the sake of comparison, I ran a comparable package but with power factor corrected electronic ballasts on our modified EU6500is (an inverter generator.) The difference between the resulting waveforms below is startling. Left: Conventional generator power w/ pkg. of non-PFC Elec. HMI Ballasts & Kino Flo Wall-o-Lite. Right: Inverter generator power w/ Pkg. of PFC Elec. Ballasts & Kino Flo Parabeam 400. The adverse effects of the severe harmonic noise exhibited above left, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral return, and instability of the generator’s voltage and frequency. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference. In other words, saving a few bucks by building your own lights can cost you a considerable amount of money in lost time or damaged equipment. For a detailed explanation for why this is, see my article on the use of portable generators in motion picture production available on our website. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Equipment Rental and Sales in Boston

Unless, your location is not available at night, it would be a lot easier to shoot night for night. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Equipment Rental and Sales in Boston.

There is something to Adrian’s concern. Using tungsten light sources when the camera’s native color balance is 5000K doesn’t make a lot of sense. Balancing tungsten to 5000K is not very efficient because full CTB cuts the output of the light by 70% in converting it to 5000K. A 1000W 3200K light becomes a 300W 5000K light when you put Full CTB on it. A 400 W HMI will give you considerably more lumens/watt than a color corrected Tungsten 1k, and use up a lot less power. It makes more sense to use HMIs to light for cameras with a native color balance of 5000K because they provide more lumen/watt and require less filtration with gels, but they are also considerably more expensive to buy or rent. While Kino Flos are a cost effective alternative to HMIs, they generally have a very broad soft light output that drops off rapidly which means the units need to be positioned close to the subject they are lighting. This characteristic makes them better suited to lighting documentary interviews than dramatic scenes like the one described here. The one exception to that rule is the Kino Flo ParaBeam fixtures. The Kino Flo ParaBeam fixtures use computer aided designed (CAD) parabolic reflectors that focus the light output at about 16 feet (5 meters). This feature makes the Kino Flo ParaBeams well suited for dramatic set lighting, because it doubles the light output of the lamps where it is needed most for lighting dramatic scenes - at a medium distance. Compared to the Kino Flo Diva-Lite, which uses the same four 55 Watt compact lamps and the same ballast, the ParaBeam 400 is twice as bright at 12' – making them a suitable key source for lighting dramatic scenes. Kino Flo also makes available for the ParaBeam fixtures a number of innovative accessories that enhance their production capabilities for HD Digital Cinema. Accessories include barndoors, a gel frame, a diffusion panel, and Honeycomb Louvers. Honeycomb Louvers are available in 90, 60 and 45 degrees and provides beam control similar to that of swapping lenses on an HMI Par. Wide Shot of Night exterior scene lit with our HD P&P Pkg. For example, on a recent independent short shot on a Red, I used a package that consisted of a 2.5kw, 1200, & 800 HMI Pars (with PFC ballasts), a couple of Kino Flo Parabeam 400s, a couple of Parabeam 200s, and a Flat Head 80. Given the light sensitivity of the Red Camera, this was all the light we needed to light a large night exterior (see pictures attached.) The PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 of our HD P&P Pkg. powered by our modified Honda EU6500is through our 60A Full Power Transformer/Distro The scene takes place behind a mall at night, rather than a school corridor at day, but the issue of color balancing of lights to the native color balance of the camera are the same: we used the 2.5 HMI par to light the deep background, the 1200 HMI par to light the near background, and the 800 Joker was mounted on a Source 4 Leko with a bug-a-beam adapter to create a window pattern on the ground from a building that doesn’t exist but you don’t see that in the movie. We used two Parabeam 400s to key the talent and a Kino Flo Flathead 80 to fill the entire scene. A Distro System consisting of a 60A Full Power Transformer/Distro, 2-60A GPC (Bates) Splitters, 2-60A Woodhead Box distributes power from a modified Honda EU6500is. Even though the generator is 100' away to reduce noise, plug-in points remain conveniently close to set. We balanced the color temperature of the lights to the Red’s native 5000K color balance as follows: the 2.5 & 1200 Pars were gelled with ½ CTB for moonlight. We put half CTO on the Joker 800 to create warm window light. We mixed 3200K tubes into the Parabeam 400 on the “window” side to create a warm key source motivated by the window. The Parabeam on the other side was gelled with ¼ CTB to create a cool key source motivated by the moonlight. Finally, we lamped the Flathead 80 with only 5500K tubes to create a slightly cool fill. To see the final results, use this link to our website where we have posted more detailed information on the lighting package we used along with production stills from the movie. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental and Sales in Boston

Most shows swap out the house Flo tubes with Movie-Tone tubes (see http://www.movie-tone.com/ for available color temperatures.) Since you are already going to the effort of gelling windows and swapping out tubes, why not balance the camera for 3200K and use 85ND6 gel on the windows and 3200K Movie-tone tubes instead. This way you can use less expensive tungsten fixtures for your supplemental lighting rather than more expensive HMI or Daylight balanced Kino Flos. As others have pointed out, flicker is a function of the ballast and not the tubes. A school may have some older magnetic ballasts which will not operate at a high frequency and so cause flicker. Even if they do operate at a high frequency, if it is not the right frequency, you can get what is callled an “eratz ripple.” Even though the ballasts put out a high-frequency cycle, that cycle stacks to create a lower frequency waveform which causes the light to pulsate. In a number of incidents, 24p video cameras and film cameras operating within a flicker-free window have picked up flicker from the “eratz ripple” effect. For this reason, the only way to know for sure is, as Phil says, shoot some tests to make sure you will not get an “eratz ripple” (use this link for more details about Flos and Flicker.) Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Equipment Rental and Sales in Boston.

I would approach this somewhat differently. To create that classic high key bright white commercial look, I would bring one of the 1200 Pars through the window on the right, as far away from the window as possible, to throw the window light onto the wall with cabinets behind the island. I would fly a branch-o-loris just outside the window to create a little leaf break-up on the cabinets. This would have the effect of creating some contrast (light & shadow on the back wall.) I would then key with the second 1200 Par through a 6x or 8x frame of half grid diffusion from camera right (the same side as the window) as if it were “sky shine” from the same window. Master shot of an iRobot commercial lit with a 4kw HMI Par (outside) & 1.8kw HMI Par (inside) powered from a 30A/240V dryer outlet through a step-down transformer/distro. Note: Sunny feel created by 4k Par on an overcast day. [/center] I would use a 4x8 floppie solid to cut the second 1200 off the back wall so as not to destroy the contrast we created on the back wall. I would use the 4’- 4 Bank Kinos from camera position for fill and a blue baby as a kicker from camera left. I would go easy on the back light with only one baby heavily blued and diffused. Left: Transformer/Distro plugged into a 30A/240V dryer outlet. Right: 4K HMI Par under rain protection powered by Transformer/Distro [/center] I did a very similar set up recently for an iRobot spot (see photos attached.) The spot contrasted the iRobot Scooba designed to clean kitchen floors to the old mop and bucket approach. For the mop and bucket approach we had a haggard looking Mom slopping water all over the kitchen floor as kids ran slipping and sliding across the floor. Instead of a 1200, we brought a 4k Fresnel through the window and keyed from camera right with an 1800W Arrimax through an 8x frame of full grid cloth. We armed in a 4’ – 4 Bank Kino as a back light. Left: Arri AS18 1800W Par powered from Transformer/Distro. Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro. [/center] Because we knew water would get everywhere, we used one of our 60A Transformer Distros on a Dryer Plug to power the 4K, 1800W HMI, and Kinos so that we could put a 100A Shock Block on the load side of the transformer/distro to provide Ground Fault protection inside around the wet kitchen floor. It was a good thing that we did, because it ended up pouring rain that day and so the Shock Block did double duty for the 4k that was outside the kitchen window. Use this link for more details about this set up. Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

A Fresnel in full flood would work better than a Leko. Typically you would thicken the water with glycerin which is a colorless, odorless, viscous liquid that is widely used in pharmaceutical formulations. The glycerin will slow down the run off of the water so that it's shadow has a chance to read on your talents face. It is easy to do with an insecticide sprayer, but will be hard to do with a hose. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Equipment Rentals and Sales in Boston.

There was a good example of this approach recently on these boards. Use this link - http://www.cinematography.com/index.php?showtopic=50698 - for a production still showing such a set up. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental & Sales in Boston

No, as Michael pointed out the Cable Compensation Loss circuitry (CCL) comes at “the cost of a 10-20% increase in current drawn by the ballast”, so you do better to bring the power to the ballast than the ballast to the power by using more head extensions. To minimize the draw of the ballast you want to make sure that the power that you bring to the ballast is at full line level. To assure that you have to eliminate voltage drop in the distro system where ever you can. Using the proper gauge distro cable for your run and load will eliminate Line Loss from tie-ins or generators. Over-sizing your generator will eliminate Voltage Drop on the generator as a function of load. If you can’t oversize your generator because you are using a portable generator, a boost transformer at the end of a 240V cable run can compensate for both Line Loss and Voltage Drop on the generator so that you have at least 115V on set. A big difference between Tungsten lights and HMIs is that with a drop in voltage the current drawn by Tungsten lights goes down, but goes up with HMIs. Besides the CCL circuitry, HMI ballasts draw more current as voltage drops because they use bridge rectifiers and capacitors to first convert AC to DC, and then use IGBTs to convert the DC to an alternating square wave. (ILLUSTRATION COURTESY OF HARRY BOX) Step 1: Rectifier Bridge converts AC power to rectified sine wave. Step 2: capacitors flatten the rectified sine wave to DC. Step 3: micro processor switching alternates polarity of DC creating an AC square wave. If you will recall from a previous post (http://www.cinematography.com/index.php?showtopic=43584), the diode-capacitor section of HMI ballasts (as illustrated above) convert the AC power to DC power by first feeding the AC input through a bridge rectifier, which inverts the negative half of the AC sine wave and makes it positive. The rectified current then passes into conditioning capacitors that remove the 60 Hz rise and fall and flattens out the voltage - making it DC. The DC is then fed from these capacitors to the power module where the IGBTs switch it into an alternating square wave. (ILLUSTRATION COURTESY OF FAIRCHILD SEMICONDUCTOR) Thin Black Trace: Rectifier Bridge converts AC power to rectified sine wave. Thick Black Trace: Stored Capacitor Voltage. Red Trace: Current drawn by capacitors once input voltage is greater than voltage stored in the capacitor (thick black trace.) As shown in the illustration above, the diode-capacitor circuit only draws current during the peaks of the supply voltage waveform as it charges the conditioning capacitor to the peak of the line voltage. After 90 degrees, the half cycle from the bridge drops below the capacitor voltage; which back biases the bridge, inhibiting further current flow into the capacitor. During this brief charging period, the capacitors must be fully charged, requiring large pulses of current to be drawn for a short duration (which explains the higher Apparent Power of HMIs.) Based upon how the diode-capacitor circuits of HMI ballasts operate, the effect of voltage drop is to decrease the interval in which the capacitors have to charge. If we compare (in the illustration above) one half cycle of a rectified sine wave at full line level (115V) to one half cycle of a rectified sine wave at 100 Volts, we see that the period during which the capacitors must recharge is appreciably shortened. Given a shorter interval to charge, the capacitors draw current in even higher amplitude shorter bursts. The diode-capacitor circuit therefore works harder, drawing more current during an even briefer charging period, increasing it’s Apparent Power or load. As a consequence protective circuit breakers may trip or fuses blow. If you still don’t entirely understand how electronic HMI ballasts work, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting. The article is available on our website. Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rentals in Boston

To set the record straight I did not say “the Arri 1800W ballast has an Apparent Power of 2600VA” as Michael Brown purports. What I said was that the “Arri 1800W ballast has an Apparent Power of 2250VA (2600 Max according to the ballast manual.)” And, I didn’t get that specification out of the manual, but from empirically testing the ballast. If we put our beliefs aside and go by the manufacturer’s specifications on the ballast (where Arri is required by both EU and US Electrical Code to provide accurate electrical specifications) the Apparent Power is between 2250VA and 2470VA. The Electrical Specifications for the Arri EB1200/1800 Ballasts If you look at these specifications (pictured above) you see that it is marked that it will draw 19A of current ("I") at 130 Volts ("U"). This works out to be 2470VA (19A x 130V = 2470VA) on the high end. And, according to the ballast’s electrical specifications if the Voltage drops to 90 Volts, the current drawn by the ballast climbs up to 25A for an Apparent Power of 2250VA (25A x 90V = 2250VA) on the low end. There is, as Michael says, a switch that turns off the CCL (Cable Compensation Loss circuitry) if the current exceeds 19.5A, but that switch does not act as a governor that prohibits the current drawn by the ballast from climbing over 19.5A if the voltage drops severely – if it did the ballast plate would specify a max current ("I") of 19.5A instead of 25A. Rather what the electrical specifications on the ballast tell us is that, to maintain it’s Apparent Power, the ballast will draw more current to compensate for a drop in voltage which is why they are called “Constant Power” ballasts. A Honda EX5500 AVR Generator powering two Arri M18 Heads with 150’ Stinger run. Rather than simply go by the electrical specifications on the ballasts, I set up an analogous situation to that described by the Original Poster to illustrate this feature of the Arri EB1200/1800 ballast. I ran 150’ of stingers (12/3 SJO cable with high grade Hubbel 15A connectors (as Michael suggested)) from a Honda EX5500 to power two Arri M18 heads. Then using a stinger pigtail with the outer jacket removed, I put a True RMS Amp probe on the “Hot” conductor. As you can see from the photos attached here, the voltage at the ballast dropped from 115V to 102.9V (from a combination of Line Loss on the cable and load on the generator) and the current climbed to 21.51A. If we do the math this works out to be an Apparent Power of 2213VA (21.9A x 102.9V = 2213.37VA.) This set up confirms my prior experience that the ballasts draw about 2250VA, but not the 2000VA that Michael purports. After a 12V drop from Line Loss and VD from generator load, an Arri M18 drew 21.51A at 102.9V Where the Honda EX5500 is capable of 23A per leg, the two M18s maxed it out. Had the generator been a 7500W modified EU6500is with a boost transformer to, not only compensate for voltage drop from load on the generator and Line Loss, but also boost the line level on set to 126V, the M18s would have drawn 17.5A each, and we could have run three of them and still have 7.5A left over. Our warehouse and some of our 20 M18 systems My point was simply that Tom’s suggestion to use M18s and a whole bunch of stingers to power them from a portable generator or wall receptacles that are few and far between was a recipe for potential disaster. Because the M18 operates so close to the threshold of a 20A circuit, they really should be operated on a real film distro system. When you can run a 60A whip and drop a Snack Box next to the ballast you won’t have a problem. But, if your style of shooting requires that you run multiple stingers to plug into a wall or generator outlet, you will likely have problems with the plug ends or receptacles overheating and tripping breakers. Guy Holt, Gaffer, SceenLight & Grip, Lighting and Grip Rental in Boston.

To understand how voltage drop in a distro system will affect the effective load of a generator, lets take as an example it’s influence on the 1800W HMIs mentioned above. Since 1800W HMIs use “Constant Power” electronic ballasts, to maintain it’s Apparent Power of 2250VA (2600 Max according to the ballast manual) they will draw more current to compensate for a drop in voltage. For instance, an overall voltage drop in a generator/distro system of 25 Volts will cause 1800W electronic ballast to draw 4 more Amps (2250VA/95V = 23.6A) than it would otherwise (very possible when you take into account not only voltage drop as a result of line loss, but also to overheating 15A stinger plug ends, and load on the generator – use this link for details.) Since the Arri Ballast has an operating range from 90-125V, it is not likely that the ballast will shut off from under voltage but it will draw 4 more amps of power than it would otherwise. Four Amps is a considerable loss in the effective capacity of a generator when you consider that a Kino Flo Parabeam 400 only draws 2 Amps. If we are able to eliminate the voltage drop in our example we would be able to operate two more Kino Parabeam 400s on our generator – given the punch of the Parabeam 400 that amounts to an appreciable increase in production capability. For these, and other reasons as well, it is important to eliminate voltage drop wherever you can. Guy Holt, Gaffer, SceenLight & Grip, Lighting and Grip Rental & Sales in Boston

I foresee a couple of problems with Tom Guiney’s suggestion to bounce a couple of 1800s into a large frame. First, electrical outlets are few and far between in parking garages and parking lots. Bringing “enough stingers…to find enough house power circuits to run them all” is a recipe for disaster with 1800W Pars. I am afraid that Arri is guilty of a bit of hyperbole when they claim the Baby Max is “the brightest light that you can plug into the wall.” Lately, they have been footnoting that claim as follows: ““Into the wall” denotes a single, 20A 120VAC electrical outlet on a single circuit.” The reason for the footnote is that many wall outlets are on 15 Amp circuits, and those that are on 20 Amp circuits probably use receptacles only rated for 15 Amps. 1800W ballasts will trip 15 Amp breakers and 20 Amp breakers if there is something else, like a computer or light, on the same circuit. Where you can't always know what else is on the same circuit, or even if it is a 20 or 15 Amp circuit when you plug into a wall outlet, it is risky to plug an 1800W HMI into the wall. Even if you were to find a dedicated 20A circuit (by unplugging a soda vending machine for instance) you may still have problems because the draw of an 1800W HMI is just too close to the threshold of a 20A circuit to operate reliably. The Arri 1800W ballast has an Apparent Power of 2250VA (2600 Max according to the ballast manual) which means it will draw 19.5 amps at 115V. Operating this close to the threshold, if there is any line loss from a long cable run, or increased resistance from an overheated/under-rated plug end, the draw of the ballast will climb over 20 Amps and trip the breaker. It has been my experience, and the experience of others (see the online forum threads below) that more often than not the stinger plug-ends overheat because most are only rated for 15 Amps. http://www.cinematography.com/index.php?showtopic=47803&st=0&gopid=337206entry337206 http://www.cinematography.net/read/messages?id=189714 The increased resistance that results from the heat causes the voltage to the ballast to drop and so it has to draw more power to maintain the 1800W load. At 110V it will draw 20.5 Amps. The power drawn by the 1800W Baby Max is just too near the operating threshold of a 20A circuit for it to operate reliably plugged into a U-Ground Edison Outlet. The same is true of operating them on the 20A circuits of portable generators. To the problem of line loss and overheating plug ends, you have the added problem that as you add load on portable generators their voltage output drops. It is not uncommon for a generator to drop 10-15 volts under full load. The 1800W ballast that drew 19.5 Amps at 115 Volts will draw 21.4 Amps at 105 Volts. It has been my experience that the Arri 1800W Baby Max works best on a real film distribution system where every circuit is 20 Amps, you know what is on the circuit because you are loading it yourself, and because you are distributing the power yourself from a tie in or generator you can bring the receptacle to the light. When you can run a 60A whip and drop a Snack Box next to the ballast you won’t have a problem. But, if your style of shooting requires that you run multiple stingers to plug into a wall or generator outlet, you will likely have problems with the plug ends or receptacle overheating. A modified Honda EU6500is supplies power to set (far left.) A Transformer/Distro compensates for line-loss of 300’ cable run (left center) to assure 120V line level to 4K HMI (far right), Speaker Stack Amplifiers, Set Monitors, Battery Chargers, & DIT station (Center.) 60A Bates Splitters, Extensions, and Gang boxes distribute power from Transformer around set (right center.) I have found that the only reliable way to power a 1800W Baby Max on wall out-lets or on portable gas generators is from a 240V circuit through a 240v-to-120v step-down transformer. A transformer will convert the 240V output into a single large 120V circuit that is more capable of powering the 19.5A load of a 1800W Baby Max. If you outfit the transformer with a 60A Bates receptacle, it enables you to use a real film style distro system that will allow you to move the generator off set (where it won’t be heard), minimize line loss over a long cable run, and provide plug-in pockets close to the ballasts. For more detailed information on using transformers on set, I would suggest you read an article I wrote on the use of portable generators in motion picture production. The second problem I have with Tom Guiney’s suggestion is that a couple of 1800s bounced into Ultrabounce won’t be enough to fill talent against the openings and hold detail outside. Without either netting the openings or substantially boosting the light levels inside, or both, when you expose for your talent, the exterior will blow out. If you expose for the exterior to hold detail, your talent will be underexposed and become a near silhouette. In my experience, if you can’t net the openings you probably need to use at least a 4k HMI par direct to pick up the interior levels. And, if you know how you can run a 4k off of regular wall outlets. For example, my company, ScreenLight & Grip, lit a segment of a special two-hour program for British Television’s Channel 5 that presented the same problem that Gleb is facing. Host June Sarpong interviewing a marine archaeologists The show told the story of the Whydah - a pirate ship that sank off Cape Cod nearly 300 years ago. In a unique TV experiment, marine archaeologists on Cape Cod dove to the wreck to salvage pirate booty live on air. In addition to the dive on the wreck, the program also included specially shot dramatic recreations of the story of the Whydah’s notorious pirate captain Black Sam Bellamy. To link between the modern-day adventures of the marine archaeologists and those of Black Sam Bellamy, co-presenter June Sarpong hosted marine archaeologists and pirate historians from a makeshift studio under a tent situated on a bluff overlooking the dive site. Host June Sarpong interviewing a marine archaeologists Where they wanted the dive site to serve as a backdrop to the makeshift studio, the show's producers wanted the Salvage Ship to be seen clearly on the water in the shots of June and her guests. This requirement created a similar interior/exterior contrast problem to the one Gleb is facing. The task of balancing interior levels to exterior levels was further complicated by the fact that it was a clear sunny day. We rigged a couple of 4kw and 2.5kw HMI Pars into the frame of the tent in order to get them as close as possible to our subjects, but even then we didn’t have quite enough output to compete against the sun outside. A 4k HMI Par was rigged overhead as a key for each subject The final ingredient for success was a double net strung across the open backside of the tent. The net further reduced the contrast by bringing the exterior levels down and in line with the pumped-up interior. The trick in situations like this is to strike a delicate balance between the interior and exterior light levels so that the net disappears to the camera without the exterior becoming overexposed and losing important detail – the Salvage Ship out on the water in this case. Another advantage to netting the background is that it takes the hard edge off of HD. It creates the illusion of a shallower depth of field or the selective focus we associate with film. A double net was stretched across the open side of the tent facing out onto the water. Where it took a 4k Par on each of the talent, plus a double net across the back, you can see that you need a lot more light to balance interiors to exteriors than 1800s bounced into Ultrabounce. Guy Holt, Gaffer, SceenLight & Grip, Lighting and Grip Rental in Boston.

The wide open space of parking lots make recording clean audio tracks particularly difficult when power is being supplied by a generator. With no building or other sound barrier within a reasonable distance to block the sound of the generator, you usually have no recourse but to put it behind your grip truck as far from set as possible. The problem with portable generators under such circumstances, even the super quiet Honda Inverter generators, is that by the time you move them far enough off set that you don’t hear them you have significant “Line Loss” (often referred to as “Voltage Drop”) from the long cable run (if you use regular cable) back to set. Low voltage on set can cause problems such as reduced efficiency and excessive heat in equipment, unnecessary additional load on the generator, and a dramatic shift in the color temperature and in the output of lights. For example, the effect of line loss on tungsten lights can be dramatic because their output falls off geometrically as the voltage decreases. For example a 1k lamp operating at 90% rated voltage (108V) produces about 68% of its normal light output – a 1kw lamp is now a 650W lamp. But, that is not all, as the light intensity decreases, so does the Kelvin color temperature of the emitted light. In the case of fluorescents, HMIs, and LEDs, because their power supplies are typically of a “constant power” type, they will draw more current as the line voltage decreases in order to maintain constant power to the lamp. In the case of generator output, voltage loss translates into an exponential loss in power. That is because, if you double the ampere load on the cable, the voltage drop also doubles, but the power loss increases fourfold. What this means is that when a distribution system has a large voltage drop, the performance of the generator (its maximum effective load) is reduced severely. For these reasons it is worthwhile understanding the dynamics of line loss and how to mitigate it under your particular circumstances. Guy Holt, Gaffer, SceenLight & Grip, Lighting and Grip Rental & Sales in Boston

To figure out how many Foot Candles (FC) you need, all you need to know is that it takes 100 FC to get an exposure of 2.8 with an ISO 100 film with a 180 degree shutter at 24 FPS (1/50th of a second shutter speed.) If your camera is 2 stops faster than an ISO 100 film, you will need 25 FC to get a stop of 2.8. Once you know how many FC you need for exposure you can figure out which lights will give you that using the photo-metrics that manufacturers provide on their websites (be wary of the photo-metrics given for LED lights.) With a little experience you begin to develop a feel what light will give you what you need in different situations. The basic problem in the situation you describe is that the sun is so dam bright. Because it generates approximately 70’000 FC, when shooting interiors with windows you have two problems: color temperature and contrast. Without either gelling the windows or substantially boosting the light levels inside, when you expose for your talent, your exterior will blow out. If you expose for the exterior to hold detail, your talent will be underexposed and become a near silhouette. If there are not many windows you can cover the windows with a combination of 85/ND9 gel. The gel both converts the exterior daylight from 5500K to 3200K and knocks down the level outside by three stops, so that lights that you can power off the wall will be effective as fill lights. But, where a roll of 85/ND9 gel will set you back $140.00, it will be expensive and time consuming to gel the windows if there are a lot of them. Without gelling the windows to 3200K, using 3200K balanced lights doesn’t make a lot of sense. Balancing tungsten to 5500K is not very efficient because full color temperature blue correction gel (Full CTB) cuts the output of the light by 70% in converting it to 5500K. A 1000W 3200K light becomes a 300W 5500K light when you put Full CTB on it. The output you get after correction is not enough to balance the sunlight coming through a window. For example an Arri 1k Fresnel at full flood puts out 183 FC at 10’ (55 FC after correction with full CTB to 5000K.) A Diva 200 puts out 14 FC at 10’. A Parabeam 400 puts out 63 FC at 10’. In my experience, if you can’t gel the windows you probably need at least a 4k HMI par to pick up the interior levels to within one or two stops of the exterior level seen through the windows (an Arri 4k HMI Par with super wide lens puts out 3577 FC at 10’.) The problem is powering such a large light. If you know how you can run a 4k off of regular wall outlets and since the new Arri M40 4k Arrimax head has an output comparable to a 12kw Fresnel you can now do a lot with what you can plug into a wall outlet. Since I’ve covered this in other posts, I won’t go into detail here. For details see an article I wrote for our company newsletter on the use of portable generators in motion picture production. This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." Of the article Harry Box exclaims: "Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working." "Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before." The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental in Boston

It sounds like a failed attempted strike of the bulb. The cause could be that the electrodes of the bulb have deteriorated to the point where it will strike some of the time but not all the time (it eventually won't strike at all.) If changing the bulb does not remedy the problem, then the "spark gap" on the head may need to be adjusted. The purpose of the Spark Gap is to apply a jolt of electricity to the lamp electrodes to strike the lamp. When striking an HMI, the ballast ramps up the voltage to the HMI head. When the potential created by the ballast becomes sufficient to jump this gap (two small electrodes in a clear plastic box) it continues to the lamp electrodes and strikes the lamp. If the spark gap is too narrow, the voltage to the lamp electrodes is not sufficient to strike the lamp. If the gap is too wide, the ballast may have difficulty creating a potential sufficient to jump the gap (possibly the case here.) This is an adjustment you can make yourself (just mark where the original setting was so that you can go back to it if that wasn't the problem.) You can use this link for more details on how HMIs operate. - Guy Holt, Gaffer, C.O.O. of New England Studios - soon to be the regions first feature production stage complex

Paul, it is not clear from your post whether the head is running and suddenly emits a high pitch sound and then shuts itself down or whether you are shutting the head down. Also, it is not clear if the high pitch sound is during initial strike or after the head has been running a while. Please clarify. - Guy Holt

You can’t judge the color rendering capability of an LED by its CRI rating because CRI ratings are easily manipulated to give high ratings while delivering poor color rendering. While Felloni might be a little better than the Litepanels, it still suffers the inherent limitations of all Phospher White LEDs using Remote Phosphor Technology to generate colors with long wavelengths. If you compare the Spectral Power Distribution Graph for the Felloni to that of a tungsten light you will see that it does not resemble that of a true black body radiator. The reason for this is that the “Stokes shift” process by which a portion of a LED’s “pump” color is transformed from shorter wavelengths to longer wavelengths has inherent limitations. A big one is that there is a tradeoff between lumen output and warmer color temperatures. For this reason all White Phosphor LEDs, even the Felloni, cut their long-wavelength output off at about 625 nm where a tungsten filament continues to generate light all the way out. Because of this rapid drop off of wavelengths above 625nm, pinks, reds, oranges, and other long wave-length colors will look dull under the Felloni, compared with how they look under a Tungsten source which continues strong all the way out on the long-wavelength end. And, since these long wavelength colors are essential to rendering a realistic flesh-tone, as you can see in the pictures above talent will look rather pale under a Remote Phosphor LED like the Felloni compared to how they will look under a Tungsten source (see my newsletter article available at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorHigh%20Output%20AC%20LEDs for details.) - Guy Holt, Gaffer, COO of New England Studios – soon to be New England’s first “from the ground up” feature production stage complex.

There is good reason to be wary about LED's ability to render a good skin tone. The inability of Phosphor White LEDs used in the Litepanel and Coolights 1x1 arrays to render color accurately has been well established in tests recently performed by The Academy of Motion Picture Arts and Sciences (AMPAS) as part of their “Solid State Lighting Project Technical Assessment.” (see http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorHigh%20Output%20AC%20LEDs for details.) In one (below) a model was photographed wearing a dress that had a number of different blue/cyan tints. Footage was shot with both a true tungsten source and a White Phosphor LED source. The tungsten-lit footage displayed all of the subtle differences in blue tones in the fabric, while the LED-lit footage, lacking cyan output, showed just a nice blue dress, without the same richness of hue. Since the light doesn’t put out much cyan, the camera/film simply can’t record it because those wavelengths are not reflected by the dress. Left: Tungsten source, Right: White Phosphor LED source. The same holds true of flesh tones illuminated by LED light. As is also evident in the pictures above, skin tones don’t reproduce well under LED lights because of the steep drop off of high frequency colors (above the 600nm cut off) such as pinks, reds, oranges, and other long wave-length colors. As the illustration below, comparing the reflected spectral distribution of a Caucasian skin tone under theoretical pure white light (an even distribution of all wavelengths) to that of a Phosphor White LED demonstrates, absent these wavelengths the skin tones look pale under LEDs because light reflected by the skin tone is likewise absent these critical long wavelength colors. Reflected Spectral Distribution of Caucasian skin tone under theoretical White Light and Phosphor White LED Light In the picture above illuminated by the Phosphor White LED, both the cyan/blue dress and the skin tone, don’t reproduce well because you can't get accurate color reflected from an object unless that color is in the light in the first place. In other words, if the light source doesn’t generate the color (cyan), it is not reflected by the object (the dress) and so the camera/film simply can’t record it. Another drawback to White Phosphor LEDs is that their color output is very inconsistent. That is because their color output is effected by a number of factors: the binning and manufacturing tolerance of their blue pump, the thermal management of the fixture, the ageing of the phosphors, and even the ambient temperature. For example, a one degree shift in the junction temperature of the blue InGaN LED (pump color) in remote phosphor LEDs, will cause a +/- 2nm shift in the dominant wavelength. If compounded by the average wavelength variation of +/- 2nm of blue InGaN LEDs, a 5nm divergence from the prescribed 455nm wavelength of the pump color will create color inconsistency of 5 MacAdams ellispses. While not readily apparent to the eye, image capture systems will easily see this variation. And, as broadcast studios lit exclusively with Phosphor White LEDs are finding out their output depreciates overtime and their color shifts much faster than the manufacturers say (see illustration below.) For more details regarding the issues surrounding the use of LED lights in motion picture lighting see our company newsletter at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorHigh%20Output%20AC%20LEDs.) - Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston.

While Tim is correct, I would like to expound upon a few of his points. It is a common misconception that circuit breakers and ground rods are there to protect you. A circuit breaker is there to prevent fire created by heat from an over-current or short-circuit and protect the equipment. The amount of current it takes to electrocute a person is much smaller than the amount needed to trip a circuit breaker. Add the fact that a ground rod will never pass enough fault current to trip an over current device and you realize that they are not there for personal safety. The only thing that will provide personal safety in wet conditions is a GFCI. To protect against serious harm from electrical shock, the circuit must be monitored by a Class A GFCI (Ground Fault Circuit Interrupter). This type of device will interrupt the circuit if it detects current leakage that is greater than 6 mA. At 6 mA, almost all adults and children can let go of the source of the shock. At higher currents, people are progressively less able to overcome muscle contractions caused by the shock, and therefore less able to disconnect themselves from the fault source. A GFCI will de-energize the circuit in less time than it takes to receive a harmful amount of current. Unfortunately, GFCIs do not operate reliably on most portable (ie Honda) generators, because they are not neutral bonded, unless they are earth grounded (but who grounds a Honda?) To make matters worse, GFCI test circuits can be misleading when they are used on portable generators that are ungrounded because they will give a false positive - that is indicate that they will work even though they will not. For detailed information on how to use GFCIs to provide ground fault protection with portable Honda generators, I would suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting. This article is cited in the just released 4th Edition of Harry Box's "Set Lighting Technician's Handbook" and featured on the companion website "Box Book Extras." Of the article Harry Box exclaims: "Great work!... this is the kind of thing I think very few technician's ever get to see, and as a result many people have absolutely no idea why things stop working." "Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights, on portable generators than has ever been possible before." The article is available online at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. Guy Holt, Gaffer, ScreenLight & Grip, Lighting & Grip Rental in Boston

Are you planning to build the LEP Space Lights yourself or use the Helio or Hive LEP Space Lights? - Guy Holt, Gaffer, ScreenLight & Grip, Lighting rental and sales in Boston

You've got some great suggestions for “grip lighting”, but on overcast days I find you still need lights? I have always found reflector boards to be useless on overcast days because there is no light to bounce, and what bounce you get is very high in color temperature. By the time you warm it up with CTO, there is nothing left. As a gaffer in New England (about which Mark Twain famously quipped “If you don’t like the weather, just wait five minutes and it will change”) I don’t go outside without both a grip and lighting package – especially if we are shooting dramatic scenes over an extended period of time. Then the issue is matching the light as the weather changes constantly. Since you are looking for low budget solutions, you probably can’t afford big HMIs and the big generator to operate them. The approach that I find works best is to shoot under a full silk with smaller HMIs. Shooting under a silk offers a number of advantages. First, it knocks down the level under it by two and half stops, which brightens the background outside the silk so that it looks like a sunny day. Second, smaller HMI lights will have more of a modeling effect in the lower ambient level under the silk. Shooting into talents' down side under a silk, I find that a 2.5 Par through a diffusion frame is a sufficient key source to create the look of a sunny day on your talent. Third, if the sun breaks through the clouds, the silk takes the directionality out of the sun so the continuity you have established with your lights is not destroyed. The set up pictured below is a good example of this approach. It is obvious by the rain cover over the lights and ballasts, and the wet sandbags, that it was overcast and raining not too long before this picture was taken. But, now that the sun is starting to break through the clouds, the silk they set up to keep the talent dry will keep the sun from washing out the modeling on their talent that they created with the 2.5 HMI back cross keys through diffusion. You can easily power this set-up of two 2.5 HMis on nothing more than a modified Honda EU6500is generator if you use a transformer to step-down its 240V output to a single 120V circuit. To record dialogue without picking up the sound of the generator, run the generator out of the back of a van or truck 300-400 ft away from set. To avoid line loss over the long cable run to the generator use a Transformer that will boost the voltage to compensate for the drop in voltage you will get over the long cable run. If you have any questions about using transformers with portable gas generators, I would suggest you read an article I wrote on the use of portable generators in motion picture production. Harry Box, author of “The Set Lighting Technician’s Handbook” has cited my article in the just released Fourth Edition of the handbook. In addition, he has established a link to it from the companion website for the Fourth Edition of the Handbook, called “Box Book Extras.” The “Box Book Extras,” site is also worth checking out because it includes other source material used for the handbook, articles by Harry Box published in other periodicals, related websites, a list of production oriented i-phone apps, as well as more in depth discussion of topics touched upon in the handbook. You can log onto the Box Book Extras site at http://booksite.focalpress.com/box/setlighting/ with our pass-code "setlighting." Use this link for my news letter article on the use of portable gas generators in motion picture production. Guy Holt, Gaffer, SceenLight & Grip, Lighting and Grip Rental & Sales in Boston.

As an Arri dealer, I have had the opportunity to play around with the prototype of the Arri L7 Fresnel. For more details, see my newsletter article on LEDs. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston

You might want to consider Kino Flo Barfly fixtures. They aren’t much bigger than the 1x1 LED panels, put out a lot more light, can be lamped daylight or tungsten, and offer much better color rendition - especially when it comes to flesh tones which is critical when shooting interviews. A distinct advantage to Kino Flos over LED panels is that their discontinuous color spectrum can be easily corrected with gels, LEDs can not. Which makes Kino Flos, in my opinion, a better key source for documentary interviews because they will render flesh-tones better. Once the green spike of Kino-Flo’s True Match tubes have been corrected by the application of minus green (magenta) gels, the resulting spectral distribution is nearly continuous and contains a greater proportion of the long wave length colors that are so critical to rendering flesh-tones accurately (see illustration below.) As can be seen clearly in the side-by-side comparisons in my newsletter article, skin-tones are significantly altered by the steep drop-off of long wavelength colors in LED light sources. Kino-Flo’s high CRI True-Match tubes, on the other hand, contain sufficient light in that critical part of the spectrum to render skin-tones realistically. Once corrected for their green spike, Kino Flo True Match tubes provide a nearly full spectrum source capable of rendering flesh tones realistically. With Phosphor White LEDs, it is nearly impossible to correct for their deficiencies with gels (use this link to see side-by-side comparisons.) A second distinction is that while the out-put of both sources depreciate overtime, when you reach low light failure of a Kino Tube after 2500hrs you can simply replace the tube. Since the cause of lumen depreciation in LED litepanels has to do with degeneration of the complete system, the remedy is not as simple. Since it is nearly impossible, even in the best designed LED luminaries, to completely protect against system degeneration, the lumen maintenance of an LED luminary is significantly less than the 50’000 hrs given by manufacturers for a single diode. For example, recent tests from the Caliper program (US Dept. of Energy) suggest that the lumen output of many LED luminaries depreciate to less than 50% after only 500hrs (see page 27 of the summary for examples of lumen depreciation after about 500 hours.) While, this might not be representative of every LED product, the vast majority of those that were tested fell far short of the manufacturers claims of lumen maintenance over 50’000hrs. When you take into account all the factors that can cause lumen depreciation and color shift over time, the useable lamp life of Phosphor White LED luminaries designed for motion picture lighting applications are probably no more than 1500 hrs. Since these types of LED fixtures generally have no interchangeable parts that can be replaced after reaching low-light failure, after 1500 hrs the fixture can only be thrown away (use this link for more details.) With Kinos you can simply replace the tubes. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston.

Good luck trying to correct the deficiencies of LED panels with gels. Even the better LED light panels, like the Litepanels, are so deficit in certain parts of the color spectrum that by the time you came up with a color gel pack to match them to a continuous light source like a tungsten or HMI light, the LED panel would put out very little light with all those gels on it. And, to make matters worse, common color meters, like the Minolta III F, are completely useless with LEDs in determining what gels to use. The meter makes its calculation of the color temperature based on an assumption that the light source has a continuous spectrum. Color readings of an LED have been shown to be misleading for both correlated color temperature and green/magenta shift. It is also a common mistake to think that a custom camera white balance can correct for the deficiencies of LEDs in every situation. Take Daryn Okada’s situation I gave as an example above. Had Daryn Okada been shooting with a digital video camera, he would have noticed the off color of the LED source immediately. But, given the limited spectral output of LEDs, his ability to remedy the problem would have been limited. If he white balanced the camera for the LED source, the background of the room beyond the doorway that was lit by tungsten lights would turn very green. In a mixed light situation such as this, the only alternative is to match the LED source to the prevalent tungsten source with a custom gel pack on the LED head. But, since gels rebalance the spectral distribution of a light source by passing the wavelength of the color that they are, gels cannot correct for these deficiencies either because there is not much light of those wavelengths to pass in White Phosphor LEDs to begin with. In other words, White Phosphor LEDS are so deficit in certain parts of the color spectrum that by the time you came up with a color gel pack to match them to a continuous light source like a tungsten light, the LED panel would put out very little light with all those gels on it. To understand why this is so, we need only look at a similar situation: the conversion of tungsten light to daylight using full CTB gel. As you can see in the Spectral Power Distribution graph of tungsten light above, tungsten light is so deficient in the blue part of the spectrum that it takes a quite saturated blue gel to balance it to daylight. In fact, the transmission coefficient of some full CTB gels is only 24%, which means that it passes only 24% of the source (see below.) That is why gelling tungsten lights is a very inefficient way to create a daylight source (a tungsten 1000w gelled with CTB becomes a 240W daylight source.) As you can see from the Spectral Power Distribution graph of the White Phosphor LED light above left, a gel pack that would match it to tungsten light would have to include a violet gel to extend its’ spectral output below 425nm. It would have to include medium blue, cyan, and turquoise gels to fill in the missing wavelengths from 465-510nm. Finally it would have to include pink, red, and orange gels to extend its’ spectral output beyond its’ 600nm cut-off. All of these gels would have to be quite saturated, since there is very little, if any, output of these wavelengths in White Phosphor LEDs to begin with. Imagine how much light you will get out of a LED light panel with such a gel pack (LED light panels put out barely enough to begin with, and have no output to waste to such accurate color correction.) Since, under most circumstances it is simply not feasible to completely match LED sources to tungsten sources with a gel pack, in mixed light situations such as these you are left, without recourse, with the off color generated by LEDs. Left: Tungsten source, Right: White Phosphor LED source. If the actress in Daryn Okada’s shot were the model in the blue/cyan dress above, you can imagine what would happen when she stepped onto the mark lit only with the LED source by looking closely at the contrasting photos above. Since, under the circumstances, Daryn Okada could not white balance for the LED source (and it would not be feasible to match the LED source with a gel pack) the rich blue/cyan hue of her dress in the left photo would turn into the simple blue of the right photo. The vibrant skin tone of the left photo would turn into the flat skin tone of the right photo, and it would have an overall magenta cast to boot. The bottom line is that color gel packs, camera white balance, or digital intermediate timing can’t bring out a color if it isn’t there to begin with. Simply by nature of their discontinuous spectral distribution, even high CRI Phosphor White LEDs will never accurately reproduce colors on screen regardless what you do on set or in post. For more details, see my newsletter article on LEDs. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston