Guy Holt

Jokers are great lights, and have some very innovative accessories. The one drawback to Jokers is that their ballasts are not Power Factor Corrected. Their poor Power Factor causes them to use power inefficiently and the harmonic currents that they generate can have a severe adverse effect on the power waveform of portable generators. Since the poor Power Factor of Jokers is commonly overlooked because of their small size, I would like to take this opportunity to explain it in detail and show how it might impact Matthew’s decision. If we look at the technical specifications for Joker Buglites, we see that the ballast of the Joker 800 draws 12.5 Amps rather than the 7 Amps you would think using Ohm’s Law (800W/115V=6.956A) This difference is between what is called “Apparent Power” and “True Power.” The ratio of “True Power” to “Apparent Power” is the “Power Factor” of the light. The Joker 800 then has a power factor of .56 (6.956A/12.5A=.556 ) Used on wall outlets, this relatively inefficient use of power is negligible because the power draw of the Joker 800 fits easily in a standard wall circuit. However, the greater Apparent Power of lights with a poor Power Factor must be factored when using portable generators. For instance, you would think that you could operate a Joker 800 on a 1000W. But, in fact, you would overload the generator because the “continuous load” rating of 1000W Generators is typically only 850W and the actual load of the Joker 800 is 1437W (12.5A x 115V = 1437W.) The greater Apparent Power of Lights with a poor power factor is not the only consideration when operating them on a generator. When you use lights sources like HMIs, Kinos, CLF lamp banks, and even LEDs, on generators it matters not only what type of ballasts the light uses, but also what type of generator you use to power it. The harmonic currents that ballasts with poor Power Factor, like the Joker 800 electronic ballast, draw can have a severe adverse effect on the power waveform of some generators. Normally, when you plug a HMI, Fluorescent, or LED light into a wall outlet you need not be concerned about the current harmonics generated producing voltage distortion. 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, that inherently noisy loads placed upon it will not affect the voltage at the load bus. Left: Waveform of grid power. Right: Waveform of conventional AVR Generator (Honda EX5500) operating non-linear lighting pkg. consisting of two Arri 1.2kw non-PFC ballasts and a Kino Flo Wall-o-Lite. However, it is an all together different situation when plugging non-power factor corrected HMI, Fluorescent, or LED ballasts, into conventional portable generators. Given the large sub-transient impedance of conventional generators even a small degree of harmonic noise being fed back into the power stream will result in a large amount of distortion in its’ voltage. Add to that, the fact that the original supply voltage waveform of a conventional generator is appreciably distorted to begin with, and you have a situation where the return of any harmonic currents by an HMI, Fluorescent, or LED ballast will result in significant waveform distortion of the voltage at the power bus (see oscilloscope shots above.) The waveform distortion caused by these harmonic currents can have a severe adverse effect not only the generator, but also other electronic equipment operating on the same power. The ballast of the Arri M8, on the other hand, has a power factor of .98 (near unity) and so draws less power (approx. 7A) and generates no harmful harmonic currents. When you consider that a Kino Parabeam 400 draws only 4A, the 5.5A difference between the power factor corrected M8 and non-power factor corrected Joker 800 can make a big difference in your production values when using a portable generator. The poor Power Factor of HMIs, Kinos, CLF lamp banks, and even LEDs, have been vexing set electricians for years. Use this link for an article I wrote for our company newsletter that explains the electrical engineering principles behind these issues and how to resolve them. 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 Rental and Sales in Boston

As long as you are shooting into the house, and not out over the lawn, you should have plenty of level from an M40. How had you planned to power it? Guy Holt, Gaffer Screenlight and Grip Lighting Rental & Sales in Boston

I know it is too late for Sean, but I thought I would update the archive for future searches. The brand doesn’t matter as much as the method of calculation used in the meter. All of the commonly used types of multi-meters are calibrated to give an “RMS” value for the measured signal, but arrive at that value using a number of different methods. Unfortunately, most of these methods assume the waveform to be sinusoidal and so when used to measure nonlinear voltages and currents, errors occur that result in false readings. For example, in an IATSE Local 481 Power Quality Workshop I developed we do an exercise where the students meter the voltage and current on a putt-putt generator (non-inverter type) while running a non-pfc 2.5kW HMI light. Since, invariably, the meters brought by the students range in quality, the readings they get range from being 84% over to 40% under what they should be. Since the consequences of under measurement can be significant - overloaded cables may go undetected, bus-bars and cables may overheat, fuses and circuit breakers will trip unexpectedly - it is important to understand how meters work and why only meters based on "true RMS " techniques should be used on power distribution systems supplying nonlinear loads.To see why use this link. Guy Holt, Gaffer ScreenLight & Grip Lighting Rentals & Sales in Boston

I don’t know the particulars of where, when, and on what HMIs were first used, but I would be very surprised if they came about as a consequence of HID lamps being used on set first. The output and color rendering of HID lamps is and always has been not up the requirements of motion picture imaging. One distinguishing feature of HMI lamps that separates them from HID lamps is the precious metals incorporated in HMI lamps to generate a near daylight spectrum. HMI lamps are also designed with a comparatively short electrode gap in order to increase output, improve luminous efficacy, and color rendering. Their increased luminous efficacy places an increased load on the bulb wall which accelerates the devitrification of their quartz envelope; which, in turn, leads to increased lumen depreciation. In other words, their brilliance comes at the expense of lamp life. Over their relatively short life of 500-750 hrs, it is not uncommon for HMI lamps to lose 15-20 percent of their initial lumen output before they fail all together. For this reason, HMI lamps were never adopted for general illumination. It took a while for manufacturers to work out all the bugs in HMI power supplies, so any discussion of “the technological developments that made them credible film lights” would have to include the advancements we have seen over the years in ballast design. Today you have a choice between magnetic and electronic ballasts; and to complicate matters even more, you have a choice between Power Factor Corrected electronic ballasts and non-Power Factor Corrected electronic ballasts. Power Factor Correction (PFC) is relatively new to HMIs and adds considerably to their cost and so you will still not find it in smaller HMI ballasts. In fact, I wouldn’t be surprised if you were not even familiar with Power Factor Correction. Since Power Factor Correction (PFC) is not mandated in this country, as it is in Europe for any electrical device that draws more than 75W, we are pretty much ignorant of Power Factor and effect that poor Power Factor can have on a distribution system and power generation source. However, any veteran film technician who has worked in the industry for more than twenty years will be quite familiar with Power Factor and Power Factor Correction (PFC.) That is because after a false start back in the 90s, all major manufacturers now include PFC circuitry in HMI ballasts in the 6-18kw range. They do so by necessity. The early line of Lightmaker electronic ballasts were nick named by film electricians “Troublemaker” ballasts because they were not Power Factor Corrected and proved that PFC circuitry was absolutely necessary in large ballasts to reduce heat and returns on the neutral, and to increase ballast reliability. But, because of the added cost, weight, and complexity of PFC circuitry, ballast manufacturers in the US still only offer PFC circuitry as an option in medium-sized 2.5-4kw ballasts. And, until very recently manufacturers did not offer PFC circuitry in HMI ballasts smaller than 2.5kw in the US (in the EU PFC circuitry in mandatory in all HMI ballasts sold.) Part of the reason PFC circuitry was not incorporated in smaller HMIs was that it did not offer a huge advantage when plugging into house power. A typical 1200W Power Factor Corrected electronic HMI ballast will draw 11 Amps at 120 Volts verses the 19 Amp draw of a non-PFC electronic ballast. While not a huge advantage when plugging into house power, the added efficiency of a PFC 1200 ballast can make a huge difference when powering a lighting package off of a portable generator. For example, when you consider that a Kino Flo Parabeam 400 draws only 2 amps, the 8 Amp difference between using a PFC 1200W electronic ballast and standard non-PFC 1200W electronic ballast, can mean the difference between running four additional Parabeam 400s on a portable generator or not. Unfortunately, it is still the case that almost every 575 - 1200W electronic ballast that you will find in a rental house or for sale used in North America will be a non-PFC electronic ballast. To this day older magnetic HMI ballasts offer a number of benefits over a non-Power Factor Corrected electronic ballast. A 1.2kw electronic ballast draws 19amps (verses the 13.5 amps of a magnetic ballast) so it will always trip the common 15amp house circuit and will trip a 20 Amp circuit 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, a 1.2kw magnetic ballast drawing only 13.5 Amps is the safer bet since it can operate on a 15 amp circuit even with other loads on the circuit. Non-Power Factor Corrected electronic ballasts are meant to be used on film sets where every circuit is 20 Amps and you know what is on the circuit because you are distributing the power yourself from a tie in or generator. If your style of shooting requires that you plug into wall outlets, you will be better served by a magnetic ballast. But that is not the only benefit to using a magnetic ballast over a non-PFC electronic ballasts. If you don’t have access to the newest PFC electronic ballasts, the older magnetic ballasts are in fact cleaner running on portable gas generators than non-PFC electronic ballasts. As mentioned above the harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional AVR generators limited the number of HMIs you could power on a portable generator. Characteristic voltage waveform of a non-PFC electronic HMI ballast on grid power (left), on power generated by a conventional AVR generator (middle), and power generated by an inverter generator (right) The adverse effects of this harmonic noise that can be seen in the middle oscilloscope image above, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral wire, and instability of the generator’s voltage and frequency. For these reasons it has never been possible to operate more than a couple of 1200W HMIs on a conventional 6500W portable gas generator. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference. The increasing use of personal computers, hard drives, and microprocessor-controlled recording equipment in production has created an unprecedented demand for clean, reliable power on set. However, now that inverter generators, like the Honda EU6500is, do not require crystal governors to run at precisely 60Hz, magnetic ballasts offer a cost effective alternative to dirty non-PFC electronic ballasts because you can operate magnetic HMI ballasts “flicker free” on inverter generators. And as mentioned above, the smaller magnetic ballasts (575-2500W) offer the distinct advantage of being less expensive and draw less power (once they have come up to speed) than the commonly available non-PFC electronic equivalents (13.5A versus 19A for a 1.2kw.) 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.” While older HMIs with magnetic ballasts are less expensive to purchase or rent, Power Factor Correction (PFC) makes the newest electronic ballasts worth the extra money when it comes to lighting with portable generators. The substantial reduction in line noise that results from using power factor corrected ballasts on the nearly pure power waveform of an inverter generator creates a new math when it comes to calculating the load you can put on a generator. Left: Grid Power w/ 1.2Kw P-2-L PFC Elec. Ballast. Center: Conventional AVR Power w/ 1.2Kw P-2-L PFC Elec. Ballast. Right: Inverter Power w/ 1.2Kw P-2-L PFC Elec. Ballast. In the past we had to de-rate portable gas generators because of the inherent short comings of conventional generators with AVR and Frequency governing systems when dealing with non-PFC electronic ballasts. The harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional AVR generators limited the number of HMIs you could power on a portable generator to 75% of their rated capacity (4200Watts on a 6500W Generator). But now, where inverter generators have virtually no inherent harmonic distortion or sub-transient impedance and power factor correction (PFC) is available in small HMI ballasts, this conventional wisdom regarding portable gas generators no longer holds true. Where before you could not operate more than a couple 1200W HMIs with non-PFC electronic ballasts on a conventional generator because of the consequent harmonic distortion, now according to the new math of low line noise, you can load an inverter generator to capacity. And if the generator is one of our modified Honda EU6500is inverter generators, you will be able to run a continuous load of up to 7500W as long as your HMI and Kino ballasts are Power Factor Corrected. And, since after ramping up, PFC electronic ballasts top off at a lower current draw than non-pfc electronic ballast, it is now possible to operate a 12kw HMI off of a couple of paralleling Honda EU6500 generators. And if that 12kw globe has one of the CAD designed ARRIMAX reflectors behind it, you have output comparable to that of an 18kw HMI Fresnel on Honda generators. Since there is nothing else that can run portable generators that can compare to an 18kw Fresnel, HMIs will continue to be the go to source when it comes to lighting day exteriors or the deep background of night exteriors. Guy Holt, Gaffer, ScreenLight & Grip Boston Lighting Rental & Sales in Boston

Given the evolution of the technology this is a huge topic. In head design you have (in chronological order) Fresnel, Par, and the new CAD designed ARRIMAX reflectors. The basic difference in head design between a Fresnel and Par is that a Fresnel gives you less output for the wattage, but the light is crisp and you will be able to cut a clean shadow edge. The subsequent Par on the other hand gives you more output, but the light is sloppy and you will not be able to cut a clean shadow edge. The newest CAD designed ARRIMAX reflectors give you nearly the crispness of a Fresnel, and more output than a Par since they do not use spreader lenses like a Par head. HMI globes were originally double-ended and then single ended globes were introduced. The newer single ended globes put out approximately 10% more light than the older double end globes and allowed manufacturers to make a more compact head design. The newer single ended heads are smaller and lighter for that reason. The history of HMI ballast design is not quite as linear as that of head design in that its’ progress is characterized by the proverbial two steps forward while making one step back. When electronic square wave HMI ballasts came on the market, they were at first thought to be the solution to all the problems inherent in running HMIs with magnetic ballasts on portable generators. Since they are not frequency dependent, it was thought at first that electronic square wave ballasts would operate HMIs more reliably on generators – even those without frequency governors. By eliminating the flicker problem associated with magnetic ballasts, they also eliminated the need for the expensive AC governors required for flicker free filming with magnetic HMI ballasts and portable generators. 

For these reasons, as soon as electronic square wave ballasts appeared on the market, many lighting rental houses replaced the expensive crystal governed Honda EX5500 with the less expensive non-synchronous Honda ES6500. The theory was that an electronic square wave ballast would operate reliably on a non-governed generator and allow filming at any frame rate, where as a magnetic HMI ballast operating on an AC governed generator allowed filming only at permitted frame rates. In practice, electronic square wave ballasts turned out to be a mixed blessing. The leading power factor caused by the capacitive reactance of the new electronic ballasts proved to have a more severe effect on conventional AVR generators than did the old magnetic ballasts. 

Since magnetic ballasts worked reasonably well on AVR generators with governors, in the past, attention was only given to portable generator features such as automatic voltage regulation, speed regulation and AC Frequency. But, given the leading power factor of electronic HMI ballasts and the problems they cause, an increasingly more important feature today is the quality of the generated waveform and the impedance of the power system. For this reason, it is imperative that today’s power generation and electrical distribution systems be designed for capacitive lighting loads, not just inductive lighting loads. This is especially true of the systems to be used in low budget independent production because these productions have traditionally relied upon portable gas generators that are more susceptible to the adverse effects of harmonic distortion. These productions are also increasingly embracing the use of HD digital cinema production tools, like inexpensive HD camcorders, laptop computers and hard drives, that require cleaner and more reliable power on set to operate effectively. If some of this terminology is foreign to you, I would suggest you read an article I wrote for our company newsletter on the use of portable generators in motion picture lighting. In it I cover the evolution of HMI ballast technology, basic electrical engineering principles behind ballast Power Factor, harmonic distortion, and how it adversely affects generators. The article is available at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. Guy Holt, Gaffer, ScreenLight & Grip Lighting Rental & Sales in Boston

The new Astra 1x1s are a vast improvement over the old 1x1 Bicolor Litepanels. They have a Television Lighting Consistency Index (TLCI) in the high 90’s, which means, according to the developer of the test, that "their color rendering deficiencies are so small that a colorist would not consider correcting them." By comparison, the old 1x1 Bicolor Litepanels tested had TLCIs in the mid 50’s, which means that a colorist would certainly want to correct the errors, and could probably achieve an acceptable result, but it would take significant time. For those not familiar with TLCI ratings, it is a means of analyzing the performance of a luminaire in the context of what color correction would be required for television broadcasting. The new Astra 1x1s are also power factor corrected with a pf of .99, where the old 1x1 Bicolor Litepanels were not and had a pf of .62. What this means is that nearly 40 percent of the power consumed by the old 1x1 Bicolor Litepanels did not go into generating light. With a near unity power factor, the new Astra 1x1s are much more efficient. One problem I find with the Astra 1x1s is that, like most LEDs, their power factor decreases as they are dimmed. In tests I recently conducted with a number of LED fixtures, the pf of the Astra 1x1 dropped from .99 to .54 when dimmed 50% (use this link to see the complete results of my tests.) (Bottom left dimmed 50%. Bottom right dimmed to 25%.) This drop in efficiency is less worrisome than the harmonic currents it also draws when it is dimmed (see the Fast Fourier Analysis above.) The harmonic currents it draws are worrisome because they can affect portable generators adversely. (Left: Grid Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Center: Conventional AVR Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Right: Inverter Power w/ 1.2Kw Arri non-PFC Elec.) Given the large sub-transient impedance of conventional portable generators, the generation of even a small degree of harmonic noise will result in a large amount of distortion in its’ voltage. Add to that, the fact that the original supply voltage waveform of conventional portable generators is appreciably distorted to begin with, and you have a situation where the generation of any harmonic currents, whether by non-PFC HMIs, Fluorescents, or LEDs will result in the significant waveform distortion of the voltage seen in the oscilloscope shot above which can lead to operational problems with the generator voltage and frequency regulation. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

The idea that you can achieve a nominally correct CCT for any color temperature between 3200 and 6500 Kelvin by mixing “tungsten” and “daylight” LEDs doesn’t stand up to scrutiny. While it seems intuitively correct that one can obtain fractional CTO and CTB color correction by means of an intermediate color balance, this approach does entail a compromise non-the-less. If on the chromaticity diagram above, you were to plot the color point of the two LEDS, all the colors that are possible by mixing them will be located on the straight red line drawn between the two points. However, the line (black line above) that would be charted by heating a black body radiator (as it turns red, orange, yellow, white, and finally blue as it is heated) is not a straight line, so it is not possible to create light that remains neutral in terms of their green/magenta shift, while mixing only two colors. And, since neither the "tungsten", nor the "daylight" LEDs in bi-color fixtures emit frequencies above their 625nm cut-off, blending them is not going to correct their deficiency of long wavelength colors, nor improve their generally poor rendition of flesh-tones. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

Not necessarily. If the issue is heat projected by a light onto delicate artwork, he can use heat-shield in front of the lamp. If the issue is raising the ambient temperature of the room, he can use a portable room air conditioner to keep the room from becoming too hot. There are better solutions than using LED sources. Even if the OP was willing make do with less than accurate color rendering, the bigger problem IMO is that gels are not calibrated for the discontinuous spectrum of LEDs and so you get unexpected and undesirable results from their use on LEDs. A good example of this is what happens when you try to convert the 6500K out-put of LEDs to 3200k with Full CTO gel. Where you can do it with some success with HMIs because there are long wavelengths in it’s more or less continuous spectrum to pass disproportionately to the blue part of the spectrum to achieve a nominal 3200K, since LEDs don’t put out much beyond 625nm, there is not much for a filter to pass to rebalance the light output to 3200K, so the “corrected” light is too cool. As indicated by the its' spectral transmission curve, Full CTO passes a disproportionate amount of the green portion of the spectrum. Another undesirable consequence comes from the fact that Full CTO is designed to pass extra green (there is a bump in the spectral transmission curve of Full CTO in the green portion of the spectrum) and so it creates, given the abundance of green inherent in Daylight LEDs to begin with, a disproportionate amount of green (creating an overall green bias) to the "corrected" light when used on 6500K LEDs (use this link to see more color tests.) Left: Tungsten lit scene with Lee 147 Apricot gel on backlights and no gel on side lights. Right: Daylight LED lit scene with Lee 147 Apricot on backlights and side lights corrected to 3200K with Lee 204 Full CTO. Note greenish cast to corrected LEDs. To remedy this problem of remote phosphor LEDs, the Photon Beam 80 has a 3200K color correction (CC) phosphor panel to use in place of Full CTO, but it lacks the intermediate grades of color correction like ¾, ½, and 1/8 CTO that are frequently used to create a warm daylight effect with HMIs. And, since the conventional approach to creating moonlight with a 3200K balanced camera/stock is to put ½ CTO on HMIs, the absence of a 4300K color correction phosphor panel is a major drawback IMO. Other manufacturers like Cineo make partial CC phosphor panels available, but at a cost well over $200/panel they are an extremely expensive alternative to a $6.50 sheet of gel. Not only are the CC phosphor panels extremely expensive, but the choice is limited to just CC equivalents to the CTO gel series. So if you are like me, and prefer to use Half CTS (Color Temperature Straw) rather than Half CTO to create warm sunlight because it is less orange, than you are out of luck. Likewise, if you want to use any of the hundreds of color gels that are available because the blue light spike that is present in LEDs, but not in Tungsten or HMI lights, means that the resulting color will be unpredictable and possibly undesirable. The OP doesn’t have to compromise his color and creativity. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

This video clearly demonstrates the point I was trying to make above. The reason the flesh-tones in this demonstration video look so pasty is that LEDS, including Remote Phosphor types, put out very little light beyond 625nm where a tungsten filament continues to generate light all the way out. Because of the rapid drop off of wavelengths above 625nm in the spectral distribution graph above for the Tungsten Photon Beam 80, pinks, reds, oranges, and other long wave-length colors look dull under the PB80, compared with how they look under a Tungsten source which continues strong all the way out on the long-wavelength end. This is very clear in the red and magenta MacBeth Chart swatches for the Tungsten PB80 below. As is evident in these swatches from the TLCI test results for the PB80, the red rendered by the PB80 (the inner square) is dull by comparison to the vibrant red rendered by tungsten light (the outer square.) Lacking vibrant long wavelength colors flesh-tones rendered by LEDs lack vitality. Yes, tungsten heads consume a lot of power and generate a lot of heat but they render healthy vibrant flesh-tones. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston.

Not necessarily. Even if the focus of this production was not the artwork or antiques in the house, but the house was only serving as the set of a period drama, there are good reasons not to use LED fixtures. Another problem with LEDs (remote phosphor included) is that color correction gels are not calibrated for their discontinuous spectrum and so you get unexpected results from their use on LEDs. This is because certain parts of the color spectrum simply are not present in the light they emit, while there is an overabundance of other parts of the spectrum compared to the light source for which the gels were designed. This problem is further compounded by the fact that white LEDs are simply blue LEDs with a phosphor counting. This presence of a strong blue light base has a huge impact on their color rendering and the way in which colot gels affect their output. For example, you know what to expect when you put a color correction gel, say ¾ CTO, on HMI or Tungsten lights, you don’t know what you will get putting that same gel on an LED light. The reason is that because of their discontinuous spectrum, the use of CC gels on LEDs have unintended and undesirable consequences. 3/4 CTO gel passes only certain wavelengths (represented by the spectral transmission curve (center)) of daylight (left) to create the color spectrum approximating that of a 3200K tungsten light (right.) The same 3/4 CTO gel applied to a daylight LED (left) passes the same wavelengths (represented by the spectral transmission curve (center)) to create an unknown color spectrum that does not approximate a 3200K tungsten light. A good example of this is what happens when you try to convert the 5500K out-put of Phosphor White LEDs to 2900k with Full CTO gel. Where you can do it with some success with HMIs because there are long wavelengths in it’s continuous spectrum to pass disproportionately to the blue part of the spectrum to achieve a nominal 2900K, since LEDs don’t put out much beyond 625nm, there is not much for a filter to pass to rebalance the light output to 2900K, so the “corrected” light is too cool. Another undesirable consequence comes from the fact that Full CTO is designed to pass extra green (there is a bump in the spectral transmission curve of Full CTO in the green portion of the spectrum) and so it creates, given the amount of green inherent in Daylight LEDs to begin with, a disproportionate amount of green (creating an overall green bias) to the "corrected" light when used on Phosphor White LEDs ( link to test results demonstrating this with a Lightpanel 1x1 Daylight Spot.) The gel pack that eventually made the Lightpanel 1x1 Daylight Spot in the test marginally similar to a tungsten light, was only able to do so at the expense of two stops – so much for the greater efficiency of LEDs. Guy Holt, Gaffer, ScreenLight & Grip, Lighting & Grip Rental and Sales in Boston

I took a look at the TLCI results for the Photon Beam LED with 3200K remote phosphor panel available on The Guild of Television Cameramen website. While the color rendering is an improvement over that of a Phosphor White LED, it suffers from the same shortcomings and is still marginal. If you compare the Spectral Power Distribution Graph for the Tungsten Photon Beam to that of a Phosphor White LED, they are similar and in no way resemble that of a true black body radiator like a Tungsten filament. The inherent limitation to the “Stokes shift” process by which a portion of a “pump” color is transformed from shorter wavelengths to longer wavelengths in Remote Phosphor LEDs is that it works in only one direction – that is why Remote Phosphor LEDs don’t emit color wavelengths shorter than their pump color. Another, inherent shortcoming to this approach to generating “tungsten” light from an LED is that there is a tradeoff between lumen output and warmer color temperatures (see my newsletter article for details.) The Tungsten Photon Beam clearly suffers from these limitations. If you compare the spectral distribution of its light output (the black trace above) to that of a Tungsten filament (the cyan trace above), the output of the Tungsten Photon Beam drops off steeply below its pump color (which is at 450nm verses 465nm of the Blue LED used in typical Phosphor White LEDs) so that it puts out no wavelengths below 400nm. By comparison a Tungsten filament continues to generate light with wavelengths well below 400nm which is why tungsten light will render violet colors better. While the Tungsten Photon Beam appears to generate more light in the medium blue-cyan-turquoise range from about 465-510nm than the typical Phosphor White LED, it is still much less than a tungsten light which is why these colors don’t reproduce as well either. Finally, its’ long-wavelength cutoff is still 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 look dull under the Tungsten Photon Beam, compared with how they look under a Tungsten source which continues strong all the way out on the long-wavelength end. Even by the TLCI rating system the output of the Tungsten Photon Beam is marginal and will require color correction in post in color critical projects like this. Yes, tungsten heads consume a lot of power and generate a lot of heat (which can be directed away from sensitive artifacts with heat shield) but they will render color faithfully. I guess the question comes down to whether you want to get the colors right in the camera or pay a colorist to fix it in post. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

If the purpose of the production is to showcase the art and antiques in the house I would not use LEDs without first conducting extensive camera tests. The problem you are likely to encounter using LEDs is that, given the discontinuous nature of their spectral output, LED fixtures are simply not capable of rendering colors accurately. You will get much more faithful color rendering from tungsten lamps with heat-shield on them, then you will get from LED lamps. Left: Tungsten source, Right: White Phosphor LED source. This inability of LEDs to render color accurately is very visible in make up, wardrobe, and props tests performed by The Academy of Motion Picture Arts and Sciences (AMPAS) as part of their “Solid State Lighting Project Technical Assessment.” (use this link for details.) In one (above) a model was photographed wearing a dress that had a number of different blue tints. Footage was shot with both a true tungsten source and a 3200K 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. 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 3200K 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 a 3200K 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. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

If you plan to plug the 1.2kw HMI Pars into wall outlets you want to make sure their ballast’s are Power Factor Corrected (PFC.) If not, they will surely trip a 15A circuit and maybe even trip a 20A circuit. The reason for this is that non-PFC HMI ballasts draw current in high amplitude pulses that include harmonic currents. I won’t go into detail here on the adverse effects that the harmonics generated by non-PFC electronic HMI ballasts can have, but anyone operating HMIs, Kinos, and even LEDs should make them selves acquainted with harmonics. (use this link for more details.) How much current a HMI ballast will draw is indicated on the manufacturer’s nameplate. Let’s take a look at one of these nameplates, since deciphering them can be as difficult as deciphering Egyptian Hieroglyphs if you don’t know how to read them. Manufacturer’s nameplate from an Arri 575/1200 Electronic Ballast specifying its’ electrical characteristics (learn how to read it.) Above is the nameplate from an Arri non-PFC 575/1200 Electronic Ballast. The first thing to look for is the ballast’s Volt-Amperes (VA), which is called “Pmax” here. Calculated as the RMS voltage times the current measured at the input to the device, Volt-Amperes is the measurement of "Apparent Power" delivered to a load, which is different than Wattage. Wattage is the True Power dissipation of the lamp calculated by integrating the product of current through the lamp and voltage over time. These may sound like they would be the same (they are in the case of incandescent lamps), however one characteristics of HMI, Fluorescent, and LED power supplies is that some of the current flowing into them is not used in the generation of light. The relationship between True and Apparent Power is called the Power Factor (PF.) Since, the Wattage will always be lower than or equal to the Volt-Amperes, PF varies from 0.0 to 1.0. As indicated on its’ nameplate, this ballast has an Apparent Power of 2290VA - which means it draws nearly twice the load of its’ 1200W output. Next to the Pmax, it also indicates that the Power Factor is .6 (cos@=.6) meaning the ballast has to draw 40 percent more power than it uses to generate lumens. The greater Apparent Power drawn by the ballast consists not only of high amplitude short pulses of current, but also harmonic currents that the ballast also draws. The next thing to look for is the relationship between Voltage (U) and Current (I). As this nameplate indicates this ballast will operate with line voltages ranging from 90 to 125 volts (US), and 180 to 250 volts (European.) You will also notice that the current (I) the ballast draws varies with the supply voltage. That is because this ballast is a “Constant Power” ballast. With constant power ballasts, if voltage drops the ballast will draw more current to maintain a constant Apparent Power - 2290VA in this case. For example, according to the nameplate it will draw 18A of current (I) at 125 Volts (U) (2290VA/125V = 18.32A.) If the voltage drops to 90V, it will draw over 25 Amps (2290VA/90V = 25.44A.) This is an important characteristic of this ballast that should be taken into account when used outside the studio on location. With an Apparent Power of 2290VA, this non-PFC constant power HMI ballast will operate very close to the threshold of a 20A circuit – too close to operate reliably unless precautions are taken. For example, according to its’ nameplate, it takes 19 Amps at 120 Volts to generate 1200 Watts of light (2290W/120V = 19A). If there is any line loss from a long cable run, the ballast will possibly draw over 20 Amps in order to compensate for the voltage drop. For instance, at 110V it will draw 20.8 Amps. To the problem of line loss, usually there is also increased resistance from an overheated plug end, which makes the voltage drop even further. Since most stinger plug-ends are only rated for 15 Amps they tend to overheat with 1200W non-PFC electronic ballasts. The increased resistance that results from the heat causes the voltage to the ballast to drop even further and so it will draw more power to maintain the 2290VA load. If the light is operating on a small generator, there will also be voltage drop on the generator because of the greater load. The voltage output of generators can drop 5-10 volts under load. At 105V, the ballst that drew 19A at 120V, will now draw 21.8 Amps and cause circuit breakers to overheat and potentially trip. For more facts/tips about power/HMIs/safety, check out an article I wrote for our company newsletter 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.” "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." Use this link for my FREE 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

Definitely Tungsten. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

It could be a light tent for table top photography of very reflective objects like jewelry. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

I'd say it was the old studio 5k. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

+1. Given your frame rate you will need some sizable fixtures and a sizable distribution system to power them. Whatever fixtures you decide to use be sure to use GFCIs on all branch circuits supplying your lights as well as your main feeder trunks. GFCIs are a must when working around water in order to avoid someone taking a potentially lethal shock. For tungsten heads larger than 2kw you will need film style GFCIs, like Shock Blocks, that are specifically designed for high amperage motion picture lights. To prevent nuisance tripping while providing Class A protection for your crew you should use an interlocking zone system approach of both Class A and Class C GFCIs. If you want to learn more about ground fault protection in wet situations, I have made available online an IATSE training curriculum that I developed for Local 481. It covers ground fault protection for everything from battery boxes to Crawford Studio generators. You will find it at this web address: http://www.screenlightandgrip.com/html/481_GFCI_Workshop.html Guy Holt, Gaffer ScreenLight and Grip Lighting Rental & Sales in Boston

This is going to be difficult to accomplish in a studio. You would need a very large one in order to get enough separation between the reflective surfaces and the chroma key wall so that the wall doesn't reflect in the mirror surfaces. But then, you would see the studio ceiling and possibly even the lights reflected in the mirror surfaces. A better approach would be to do a simplified version of the Pinewoods Malaysia water tank pictured below. That is shoot outside on an overcast day with a 20x40 greenscreen rigged at a distance so it won't reflect in your mirror surfaces. This way you will see the actual sky reflected in the mirror surfaces. You will have very naturalistic even light for the overcast segment because you are using natural light. The greenscreen will be lit very evenly by the natural light as well. For the sunny day sequence, all you will need to do is add a large HMI to create some contrast on your talent. As long as you don't use the HMI to back light your talent, it won't reflect in the mirror surfaces. To avoid the expense of renting a large diesel generator to power the HMI, you could use the new Arri M90, which has the output of a 12kw par, but will run on the 120A output of a couple of paralleled Honda EU6500 generators. Since the M90 draws only 84A, you will have 36A left over for set power, which is more than enough. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

Two more things I forgot to mention. You must also make sure the generator is running +/- .25 cycles of 60Hz (i.e. 59.75-60.25Hz.) Make sure the generator has a Hz tuning knob on its' control panel and if it doesn't, make sure you find out how to tune the generator's speed on it's governor inside the alternator compartment. Most of the 45kw WhisperWatt generators don't have digital meters, so be sure to bring a digital multi-meter in order to get an accurate measurement of HZ. And since, a 12kW magnetic ballast wastes roughly 25% of the power that it uses in Inductive Reactance, only a true RMS meter is capable of reading the load drawn by magnetic HMI ballasts, so be sure to bring one with you. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental & Sales in Boston

You won’t run out of juice, but there are a few traps that you can easily get caught in if you are not careful. First, magnetic HMI ballasts will draw more current than you would think. Because of something called Power Factor (PF) a 12kW magnetic ballast will draw more than the 50A that you calculated using Ohm’s Law (W=VA.) In realty, a 12kw magnetic ballast may draw up to 130-140 Amps (65-70 Amps per leg at 208V.) In magnetic HMI ballasts, through a phenomenon called Inductive Reactance, the multiple fine windings of the ballast transformer induces considerable current, called Reactive Power, that is in opposition to the primary current, causing the primary current to lag behind voltage, a reduction of current flow, and an inefficiency in the use of power. Put simply, the ballast draws more power than it uses to create light. If, in this situation, you were to measure the current (using a Amp Meter) and voltage (using a Volt Meter) traveling through the cable supplying the magnetic HMI ballast and multiply them according to Ohm’s Law (W=VA) you would get the “Apparent Power” of the ballast (expressed as KVA.) But, if you were to instead, use a wattmeter to measure the actual amount of energy being converted into real work (light) by the ballast, after the applied voltage overcomes the induced voltage, you would get the “True Power” of the ballast (expressed as KW.) The difference between Apparent Power and True Power, or the additional power required for the applied voltage to overcome the induced voltage, is the Reactive Power (expressed as KVAR.) The ratio of True Power to Apparent Power is called the “Power Factor” of the ballast. The favorite analogy electricians like to use to explain these terms is that if Apparent Power is a glass of beer, Reactive Power is the foam that prevents you from filling it up all the way, so that you are left with less beer or Ture Power. In other words, the thirst-quenching portion of your beer is represented by KW in the figure above. The foam is represented by KVAR. The total contents of your mug, KVA, is this summation of KW (the beer) and KVAR (the foam). In our beer mug analogy, Power Factor (P.F.) is then the ratio of Beer (True Power) to the entire volume of the mug (beer plus foam or Apparent Power.) Thus, for a given KVA: the more foam you have (the higher the percentage of KVAR), the lower your ratio of KW (beer) to KVA (beer plus foam). Thus, the lower your power factor. Or, the less foam you have (the lower the percentage of KVAR), the higher your ratio of KW (beer) to KVA (beer plus foam). In fact, as your foam (or KVAR) approaches zero, your power factor approaches 1.0. When lights with a low power factor are used, a generator must be sized to supply the apparent power (beer plus foam), even though only the beer (true power) counts as far as how much actual drinking is possible. Our beer mug analogy is a bit simplistic. In reality, when we calculate KVA, we must determine the “vectorial summation” of KVAR and KW. Therefore, we must go one step further and look at the angle between these vectors. To understand this concept let’s use the analogy of a man dragging a heavy load as illustrated above. The man’s Working Power (or True Power) in the forward direction, where he most wants his load to travel, is KW. Unfortunately, the man can’t drag his load on a perfect horizontal (he would get a tremendous backache), so his shoulder height adds a little Reactive Power, or KVAR. The Apparent Power the man is dragging, KVA, is this “vectorial summation” of KVAR and KW. The “Power Triangle” below illustrates this relationship between KW, KVA, KVAR, and Power Factor: In an ideal world (one without gravity), the man wouldn’t have to waste any power along his body height and so the KVAR would be very small (approaching zero.) KW and KVA would be almost equal and so the angle (formed between KW and KVA) would approach zero and the Cosine would then approach one. Power Factor would then approach one. For a light to be considered “efficient”, the Power Factor should be as close to 1.0 as possible. Where a typical 12kW magnetic HMI ballast draws 130-140 Amps to generate 12000 Watts of light (KW), the Power Factor is .74 (PF = KW/KVA=12000W/16200W= .74). In other words, a 12kW magnetic ballast wastes roughly 25% of the power that it uses in Inductive Reactance. A second 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, which is different than their higher reactive load discussed above. 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.” Users of 2.5kw HMIs on portable generators constantly make this mistake. Even though a 2.5kw magnetic ballast draws approximately 26 amps they find that they do not run reliably on the 30A/120V twist-lock receptacle on putt-putt generators. That is because even though the twist-lock receptacle is rated for 30 Amps conventional 6500W generators are only capable of sustaining a peak load of 27.5 Amps per leg for a short period of time. Their continuous load capacity (more than 30 minutes) is 23 Amps per leg. And if there is any line loss from a long cable run the draw of a 2.5kw magnetic ballast will climb to upward of 30 Amps. Add to that the higher striking load and you begin to understand why the breaker trips. To make matters worse, the lagging power factor caused by the inductive reactance of the magnetic ballast kicking harmonic currents back into the power stream causes spikes in the supply voltage that can cause erratic tripping of the breakers on the generator or ballast. In my experience the load of a 2.5kw magnetic ballast is too near the operating threshold of a 6500W generator for it to operate reliably except on the generator’s 240V outlet using a 240V-to-120V step-down transformer/distro like the one we make for the Honda EU6500s & EU7000s. For these reasons, I would not put any other loads on the two power legs supplying the 12kw ballast. If you have additional lighting loads on the same leg, and no head-room, the higher striking load of a 12kW magnetic ballast may push the entire load over the breaker’s threshold. If you must add additional lighting loads to the same legs, always strike the 12kW magnetic ballast first and wait until it settles down before turning on any other lights on those two legs. Finally, magnetic ballasts in general are not forgiving when it comes to flicker. The problem with them is that the light intensity of a HMI powered by a magnetic ballast follows the waveform of the supply power and increases gradually until it peaks and then decreases. Since there are two peaks per cycle (+ & - ), the light pulses twice every AC cycle or 120 times a second (see illustration below. ) This fluctuation in the light output is not visible to the eye but will be captured on film or video if the frequency (Hz) of the AC power is not precisely synchronized with the film frame rate or video scan rate. If the AC Frequency of the power were to vary, a frame of film or video scan, would receive more or less exposure depending upon the exact correspondence of the film/video exposure interval to the cycling power waveform because the light intensity is pulsating at twice the AC frequency. 
 The sinusoidal 60Hz current of a magnetic ballast (left) creates a pulsating light output (right) Electronic square wave ballasts eliminate the potential for flicker by squaring off the curves of the AC sine wave supplying the globe. Squared off, the changeover period between cycles is so brief that the light no longer pulsates but is virtually continuous (see illustration below.) Even if the AC Frequency of the power were to vary, a frame of film or video scan, would receive the same exposure because the light intensity is not pulsating but nearly constant. In other words, electronic ballasts are “flicker free” because they square off the power sine wave which causes an increase in the duration of the peak level of light output so that the light is on more than it is off. Electronic HMI ballasts are also called “square wave” ballasts for this reason. The refined square-wave signal of an electronic ballast (left) creates virtually even light output (right)(Illustrations courtesy of Harry Box So the last downside to using magnetic ballasts is that you are restricted to using only certain safe frame rates and shutter angles (use this link to tables of safe speeds.) 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. For more detailed information on using magnetic HMI ballasts on portable generators, I would suggest you read a white paper I wrote on the use of portable generators in motion picture production that will be available soon as an e-book from the Academy of Production Technology Press (APT.) Harry Box, author of The Set Lighting Technician’s Handbook has cited my article in the 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 original white paper is still available online for free at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html. - Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

If it is a day scene in the typical above ground parking garage Litepanels won't cut it because of the extreme contrast between the exterior and interior of the parking garage. They are usually poorly lit and very dark, so unless you can shoot your talent as silhouettes against the exterior city-scape you will need to do some lighting in order to keep the exterior from blowing out. I would think you would need at least 1200 Pars through diffusion frames to light any size scene. The problem is going to be powering them since parking garages are not well wired. You can usually find an outlet next to the stairwell that was put there for a vending machine. If there is a vending machine there already you will have to generate your own power. The problem with using portable power in garages is that they are echo chambers, so what I would suggest you do is put a Honda EU6500 on the level above, and then drop down from the outside a cable plugged into its’ 240V receptacle. The reason to go 240V is that it will enable you get 400-500ft away from the generator so that you don’t hear it and then you can use a step-down transformer/distro with boost taps to compensate for the voltage drop on the long cable run. That way you will have full 120V line level on set and won’t hear the generator on your audio tracks. Use this line for more details. Guy Holt, Gaffer ScreenLight & Grip Lighting Rental & Sales in Boston

Not exactly, the reflector has nothing to do with filling the back side of the Fresnel lens. It is a common misunderstanding is that the reflector collimates the light of a Fresnel head. In fact, the purpose of the reflector is to double the intensity of its' output. When the light-emitting filament of the bulb is placed near the center of curvature of a spherical, concave polished mirror reflector, the reflecting surface creates an image of the filament. That image is located in the same plane, but slightly displaced from the filament itself. This has the effect of doubling the amount of light forward projected from the locale of the lamp filament. In other words, without the reflector, "this reflector light" (the dashed lines in the illustration above) would have been lost in the back of the lamp housing. With a reflector, these rays of light are collected and sent back to their point of origin where they emanate forward, parallel with the direct rays of light from the filament (the solid line in the illustration above), towards the back of the Fresnel lens where they are together collimated by the lens (for this reason the filaments of the bulbs used in Fresnel heads are designed with an open geometry to minimize blocking of the retro-reflected light - making them not quite an ideal point source.) Now that all the light that emanated forward and back, emanates forward from a single point within the fixture (the filament and its mirror image), the light projected forward is doubled. Quantum dot LED fixtures like the one being discussed here do not benefit by this light doubling action which is why they tend to be weak by comparison to traditional tungsten Fresnels. Use this link for other features of traditional quartz Fresnels that LED Fresnels have not been able to duplicate. Guy Holt, Gaffer ScreenLight & Grip Lighting Equipment Rental and Sales in Boston

One of the biggest challenges in situations like this is getting light into the eyes of your talent – especially kids since they are so low to the ground. If you don't, their eyes will look dark and bruised because the very toppy light of the overhead fluorescents won't dig into their eye sockets. You also may want to consider using a combination of hard and soft light to create contrast in a situation where the overhead fluorescent lighting is usually very flat. The pictures attached are from short film I lit called "Act Your Age" that takes place in a senior center, but I have taken a similar approach to school classrooms whenever there was an opportunity to do rigging. To create contrast, we brought a 6k HMI par in the windows on one side of the room. But, with contrast comes the necessity to fill. If you are fortunate enough to have a drop ceiling in the classroom, you can take the approach we did in "Act Your Age", where we hung 4'-4 Bank kinos with Opal coved below the fixture to make a "Bay Light." Coving the Opal under the light, redirects it horizontally so that it will dig into the talents eyes. As you can see here, with the right rigging equipment, you can use drop ceilings like a studio grid. Use this link for more pictures of productions that used drop ceilings on location as if they were a studio grid. Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston

A 10k doesn't necessarily require more hands. You can parallel two unmodified Honda EU6500 or EU7000 generators for 100A output thereby eliminating the need for a large diesel tow plant. But, since that 100A is at 240V, you will need a 100A 2 40-to120V step-down transformer/distro. Use this link for more details about this approach. Guy Holt, Gaffer, Lighting and Grip Equipment Rental & Sales in Boston

As bright as some 18k Fresnels, the new Arri M90 is a less expensive option. Pairing a new 9 kW HMI lamp with the MAX reflector of the ARRIMAX, the new ARRI M90 creates diverging parallel rays to produce a crisp light with even distribution through a wide spot/flood range. (The light generated by the CAD designed Max Reflector of the new M90/60 is incredibly bright and sharp.) The result is a lens-less open face fixture with a quality of light close to that of a Fresnel. The elimination of spread lenses like those used on HMI Pars makes the ARRI MAX reflector lamp heads comparable in output to par configurations of a higher wattage. In fact, the M90 is brighter than some 18K Fresnels on the market. (The Active Line Filtration (ALF) of the new ARRI EB 6000/9000 ballast makes it an incredibly efficient and clean load.) To power the new M90 head, ARRI has engineered a dual wattage ballast (6 & 9kw) with Active Line Filtration (ARRI's system of Power Factor Correction.) The advanced electronics of the ballast makes it incredibly efficient and it generates virtually no harmonic noise. (The combined 100A output of paralleled Honda EU6500s is sufficient to operate the new Arri M90 as well as additional set lighting.) Drawing only 84 Amps, the M90 can operate on the combined 100A output of paralleled Honda EU6500s. Not only is this approach a lot less expensive than using an 18kw, it is also a lot easier to set up. Use this link for more details about this approach. Guy Holt, Gaffer, Lighting and Grip Equipment Rental & Sales in Boston