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Chinese Lanterns


Jase Ryan

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So where do you get the right Chinese lanterns for film lighting? I know you don't use the paper ones you get at the dollar stores, so what do the professionals use? And what about the bulbs???

 

Thanks!

 

The paper ones do get used on professional shoots.

It all depends on the budget.

 

I like to put a photoflood in those.

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I get mine from Ikea, but that's only so I can grab a cinnamon bun on the way out.

I use clear tungsten bulbs or photo floods or sometimes those new fangled halogen screw ins. Depends what I bought for the production in terms of practical bulbs.

Make sure you get a big enough lantern for the bulb you wanna use.... some of 'em get hot!

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I get mine from Ikea, but that's only so I can grab a cinnamon bun on the way out.

I use clear tungsten bulbs or photo floods or sometimes those new fangled halogen screw ins. Depends what I bought for the production in terms of practical bulbs.

Make sure you get a big enough lantern for the bulb you wanna use.... some of 'em get hot!

 

The paper ones from Ikea work fine, I generally stick with the two larger sizes (12", 16"?). I've put 200w tungsten and 150w medium screw base halogen bulbs in them without issues. But you get what you pay for, low purchase cost + cheap soft light = light source that is difficult to control or flag off from unwanted areas.

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I think it's 12" and 18" but i'm not sure, from Ikea. My biggest issue with them is mounting, but that's what gaff tape is for. As for flagging/control, I use black construction paper and tape. What I like to to is buy a few of the lanters as extras so once ons is tapes to say kill the bottom 1/2 I leave it like that for duration and use it till it's to torn up to work. I think the largest I went was a 300W bulb, in the big one but, if you do this, only strike it when you're about to roll and kill it on cut so as to keep fire risks down. I have a switch wired into a few extension cords for this purpose (works great with any light!)

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Paper lanterns are nice and cheap. There are more expensive types made from fabric. Chimera, JEM, etc.

 

You get photofloods and photo enlarger bulbs (211, 212, 213) from camera supply stores and expendable supply stores, or online. But there are regular light bulbs sold up to 300w too.

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I've successfully used as much as 1000 watts in 23" china balls.

I'd keep an eye on them then and not run them for extended periods, though.

You don't need to switch them off after every take, but I wouldn't keep them on for hours.

Also don't cover the top and bottom hole so natural air convection won't be hindered.

At those power levels you also have to be a bit careful with flagging (or even spraying!) them black,

because this is what will absorb heat radiation and thus burn them up.

 

You hear the paper crackling from the evaporating residue humidity when you switch the lamp on... :ph34r:

 

Greetings,

Marc

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It makes sense not to cover the top to keep airflow going, but are you saying not to cover the bottom either? is this with any size bulbs or only 1000W? Because that would kinda be bad if there was a harder spot coming straight down!

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Here ya go: http://www.filmtools.com/lantern-lock-china-ball-system.html

 

I really like the Lanterlock fixtures, they make it easy to rig them anywhere you want with standard grip gear. They are also a lot safer than having a free hanging fixture inside. You can always build your own if you're electrically inclined. I like the 24" and 12" sizes, wrap them in blackwrap or pin some duvetyne to the outside to control the spill.

 

Paper lanterns are cheap and work well, they'll get trashed after a few shoots anyway so just buy more for a few bucks. If you want something built to last, the Chimera pancake lanterns are the way to go. A lot more expensive though.

 

*I always keep china balls on a hand squeezer (500w dimmer) and turn them off whenever they're not in use.

Edited by Satsuki Murashige
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I prefer the quality of light from the paper lanterns to a chimera. I got a dozen or so a few years back from here: http://asianideas.com/naturalwhitepaperlanterns.html

 

Filmtools has them: http://www.filmtools.com/chinlan.html

 

Regular photo floods get extremely hot, so I’ve started getting these and they’re great-they are much larger than a regular photo flood. I’d recommend at least a 30” lantern.

 

Eiko sp85 50 med: http://www.amazon.com/Eiko-Self-Ballasted-...t/dp/B000IBQ68G

 

I go to home depot, buy ceramic sockets, and ungrounded stingers (I’m not an electrician so that’s probably bad advice), cut off the female end and assemble the socket to the cable.

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I find duvetine cloth too heavy to hang on one side of a lantern without it tipping in that direction.

 

What I like to use is this thin black plastic tablecloth material you can get at any cooking supply store like Smart & Final.

 

The ikea china balls are cheap enough that I got a bunch and spraypainted some of them for spill control. I have a few that have the top half spraypainted flat black. A few have one side hemisphere painted black. It's not the same as a skirt but it saves you from having quite so much fabric or blackwrap hanging there.

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The ikea china balls are cheap enough that I got a bunch and spraypainted some of them for spill control. I have a few that have the top half spraypainted flat black. A few have one side hemisphere painted black. It's not the same as a skirt but it saves you from having quite so much fabric or blackwrap hanging there.

What kind of paint are you using Chris? Some kind of non-flammable variety?

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Regular photo floods get extremely hot, so I’ve started getting these and they’re great-they are much larger than a regular photo flood. I’d recommend at least a 30” lantern.

 

Eiko sp85 50 med: http://www.amazon.com/Eiko-Self-Ballasted-...t/dp/B000IBQ68G

 

I go to home depot, buy ceramic sockets, and ungrounded stingers (I’m not an electrician so that’s probably bad advice), cut off the female end and assemble the socket to the cable.

 

This post gives me an idea. I love the quality of Helium balloon lights but they are too expensive for anything but a feature budget. To create a poor mans version of a helium balloon I have thought about using a large paper china lantern (48”) and the 200 Watt 8u CFL bulbs pictured below in the fixture pictured below.

 

http://img.tradekey.com/images/uploadedima...70423031229.jpg

 

http://www.inspironphoto.com/index.php?mai...mage&pID=51

 

With this fixture, I can cluster nine of the 200W CFL together and produce the tungsten equivalent of a 7650W Tungsten balloon. Since CFLs generate hardly any heat there is no fire hazard. The CFL bulbs will pull around 15 amps total so shouldn’t overload the fixture or a standard household circuit. For night exteriors I can lamp it with 5000K CFL bulbs and power it with a portable generator and still have enough power on the generator to run several small HMIs and as well. Does anyone see any reason this setup wouldn't work?

 

- Isabelle Landers, Gaffer, Nashua, NH

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Genny could cause flicker or fry the ballasts of 'em, also they won't like being too cold. I've used CFLs that just won't strike well, or at all, below 40f. Aside from that, not really. Biggest issue would be getting it up as high as easily as a helium balloon light.

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What kind of paint are you using Chris? Some kind of non-flammable variety?

 

Just plain old cheap flat black spraypaint. This is for about 300W and down, so I can't really comment on how flame retardant the paint is or isn't.

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Genny could cause flicker or fry the ballasts of 'em, also they won't like being too cold. I've used CFLs that just won't strike well, or at all, below 40f. Aside from that, not really. Biggest issue would be getting it up as high as easily as a helium balloon light.

 

Why would they flicker on a generator? The high-frequencies at which CFLs operate, 20,000 - 50,000 Hz, make them essentially flicker-free.

At those frequencies the period of time between the off and on pulse of each cycle is so short that the illuminating phosphors do not decay in light output. Like the glowing tungsten coil of an incandescent lamp, the fluorescent phosphors become essentially continuous and so are flicker free at any normal frame rate or shutter angle.

 

Does anyone see any reason this setup wouldn't work?

 

To address the original poster’s question. The bulb pictured won’t fit in the Softbank fixture pictured. The softbank fixture has closely-spaced medium-base (E27) sockets, but the 200W CFLs are mogul base (E39) and about 5 inches in diameter. Even if they did fit, it wouldn’t work. Nine 200watt 8u CFL bulbs will not draw 15 amps but close to 30 Amps. You will not be able to use it on a household circuit, you will likely overheat the neutral in the light, and if you were to power it on a portable gas generator you can expect power problems (not flicker) because this set up will generate severe harmonic distortion in the power supplied by the generator.

 

I know I can have a tendency to go on too long in my posts. But, I find again and again that because of the brevity of the posts, online forums like this are filled with blanket assertions based upon erroneous assumptions or conventional wisdom. Since a little knowledge can be a dangerous thing when it comes to handling electricity, I feel it necessary to explain briefly why Isabelle’s set up will not work. For a more detailed explanation, 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, is a more detailed explanation of the basic electrical engineering principles behind power factor and how it can adversely effect generators. The article is available on our website.

 

What Isabelle is failing to take into account is that the 120V versions of the 8u CFL bulbs have a power factor of .5.

Since power factor is commonly overlooked in the design and implementation of lighting systems in motion picture production applications, I would like to take this opportunity to explain it in detail and show how it effects Isabelle’s ballon set up.

 

If we look at the technical specifications for a representative 200 watt 8u CFL bulb below (available at http://www.maxlite.com/PDFs/FocusSheets/HighMax.pdf), we find that with a power factor of .5 the bulb in fact draws 3.3 Amps. The difference between the actual current drawn by the bulb (3.3A) and the 1.66A Elrosten calculated a 200W bulb should draw using Ohm’s Law (W=VxA), is the difference between what is called “Apparent Power” and “True Power.”

 

200w8uCF_bulb_spec.jpg

Specifications for Maxlite 200W 8u CFL Bulbs

 

If, in this case, you were to measure the current (using a Amp Meter) and voltage (using a Volt Meter) traveling through the cable supplying the CFL bulb and multiply them according to Ohm’s Law (VxA= W) you would get the “apparent power” of the bulb (120V x 3.3A = 396W). 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 of the CFL bulb you would get the “true power” of the bulb which in this case is specified by the manufacturer as 200W. The ratio of “true power” to “apparent power” is called the “power factor” of the bulb.

 

A favorite analogy electricians like to use to explain power factor is that if apparent power is a glass of beer, power factor is the foam that prevents you from filling the glass all the way up with beer. When lights with a low power factor are used, the distribution system must be sized to supply the apparent power (beer plus foam), even though only the true power (beer) counts. What accounts for this discrepancy between Apparent Power and True Power?

 

To understand the power factor of a CFL bulb, and its’ effect on the power supply, it is helpful to compare it to an incandescent bulb. An incandescent light is a simple resistive load. The high resistance of its tungsten filament creates heat until the filament glows - creating light. As we see in the oscilloscope shot below, of a 25W incandescent bulb operating on grid power, the current is always proportional to the voltage (current is represented on the scope as the voltage drop on a 1 Ohm resistor.)

 

Incan_Waveform.jpeg

Current and Voltage Waveform of a ACEC 25W Incandescent bulb

 

If the applied voltage is sinusoidal, the current generated is also sinusoidal. That is, the current increases proportionately as the voltage increases and decreases proportionately as the voltage decreases. Since the peak of the voltage corresponds to the peak in current, the voltage and current are also in phase and so have a unity power factor (Power Factor of 1.)

 

The voltage and current waveforms below of a CFL bulb operating on grid power is very different from that of the incandescent light above. The most noticeable difference is that the current, generated by the CFL bulb, no longer proportionately follows the nice smooth sinusoidal voltage waveform supplied to it by the power grid. Rather, it has been distorted by electrical components in the ballast of the CFL bulb so that it instead consists of sharp spikes in power that quickly drop off over a short duration. A second distinguishing characteristic is that the peak of the voltage no longer corresponds to the peak in current. The current now “leads” the voltage by 1.7 micro seconds. The voltage and current are no longer in phase as in the case of an incandescent bulb, but instead exhibits what we call a leading power factor.

 

The distorted current waveform and leading power factor exhibited here is caused by components in the electronic ballast which use only portions of the voltage waveform, draw current in quick bursts, and then return the unused portions as harmonic currents that stack on top of one another, creating harmonic distortion that pulls the voltage and current out of phase. This creates an opposition to the flow of current that is called capacitive reactance. Where capacitive reactance leads to an inefficient use of power (lots of foam), and the harmonic currents generated can have severe adverse effects on other equipment operating on the same power, it is worth exploring the cause of capacitive reactance and the source of the harmonic currents in more detail.

 

schematic_CFL_ballast.jpg

Typical schematic of CFL electronic ballast: L-to-R consists of half-bridge rectifier, conditioning capacitor, DC/AC Inverter

 

The electronic ballasts of self ballasted CFLs, are very similar in design to the high frequency ballasts used in fluorescent movie lights in general (Kino Flo, Lowell, etc.) All electronic fluorescent ballasts are essentially AC-to-AC power converters in that they convert line-frequency power from the utility line (60Hz) to a high-frequency AC power (20’000-50’000 Hz) to excite the gases in the fluorescent lamp so that they glow continuously. The diagram above illustrates the typical components that make up the high-frequency electronic ballasts found in most all high frequency fluorescent movie lights and CFL bulbs.

 

SMPS_Rectified_Power_Flo.jpg

Step 1: Rectifier Bridge converts AC power to rectified sine wave. Step 2: rectified sine wave is flattened to DC by conditioning capacitor.

 

They consist, first, of a diode-capacitor section that converts the AC input power to DC power, and then an inverter section that converts the DC power back to a high frequency AC power that ignites the lamp gases. The diode-capacitor section converts the AC power to DC power by first feeding the AC input current through a bridge rectifier, which inverts the negative half of the AC sine wave and makes it positive. The rectified current then passes into a conditioning capacitor which removes the 60 Hz rise and fall and flattens out the voltage - making it essentially DC. The DC is then fed from the conditioning capacitor to the inverter section which typically consists of a pair of MOSFETs (metal–oxide–semiconductor field-effect transistors) which generate the high frequency (20-50kHZ) AC waveform. Where, the harmonic currents produced by electronic fluorescent ballasts are primarily generated by the diode-capacitor section of the ballast, lets look at how this circuit works in more detail.

 

Working_of_CFLs.jpg

Yellow Trace: Rectifier Bridge converts AC power to rectified sine wave. Blue Trace: Stored Capacitor Voltage. Red Trace: Current drawn by capacitors once input voltage is greater than voltage stored in the capacitor (Blue trace.)

 

As shown in the illustration above, the diode-capacitor circuit only draws current during the peaks of the supply voltage waveform and charges the conditioning capacitor to the peak of the line voltage. Since the conditioning capacitor can only charge when input voltage is greater than its stored voltage, the capacitor charges for only a very brief period of the overall cycle time. 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. Since, during this very brief charging period, the capacitor must be fully charged, large pulses of current are drawn for short durations. Consequently, electronic ballasts, draw current in high amplitude short pulses. The remaining unused current feeds back into the power stream as harmonic currents.

 

These simple diode-capacitor circuits are used in CFL bulbs and in many fluorescent movie lights because they are compact and inexpensive. However, they have a number of drawbacks. For instance, notice how big the input current spike (red trace above) of the diode-capacitor circuit is. Without power factor correction, the in-put bridge rectifier requires a large conditioning capacitor at its output. This capacitor results in line current pulses (as seen in our oscilloscope shot above) that are very high in amplitude. All the circuitry in the ballast as well as the supply chain (the generator, distribution wiring, circuit breakers, etc) must be sized to carrying this high peak current (the foam in our analogy). Also notice that the line current pulses are narrow, with fast rise and fall times. Since the rectifying circuit uses only the peaks of the voltage waveform, they generate high harmonic content as the unused portions of the voltage waveform are returned as harmonic currents (see graph below.)

 

CFL_Harmonic_Distro.jpg

Distribution of Harmonic Currents generated by CFL bulb

 

These harmonic currents stack on top of one another creating harmonic distortion that creates an opposition to the flow of current; and, as we see in the oscilloscope shot above, pulls the voltage and current out of phase. When the power is supplied by a conventional generator, these harmonic currents can also lead to severe distortion of the voltage waveform in the power distribution system (see below for more details.) Finally, the fast rise time of these harmonic currents can cause Radio Frequency Interference (RFI) problems. For this reason, on their website Lowell warns about their compact fluorescent (CFL) fixture, the Lowel Ego, that: “The lamps may cause interference with radios, cordless phones, televisions, and remote controls. If interference occurs, move this product away from the device or move to a different outlet” (http://www.lowel.com/ego/lamp_info.html.) While self ballasted CFLs generate the most severe harmonics, all electronic ballasts (both fluorescent and HMI) generate harmonic currents (see table below.)

 

Table_THD_Flo_Ballasts.jpg

 

Besides possible RFI problems, you need not be concerned about current harmonic distortion producing voltage distortion when you plug an electronic ballast (fluorescent or HMI) into a wall outlet. The impedance of the electrical path from the power plant to the outlet is so low, the distortion of the original applied power waveform so small (less than 3%), and the power plant generating capacity so large by comparison to the load, that harmonic currents fed back to it will not effect the voltage at the load bus (electrical outlet.) However, it is an all together different situation when plugging an electronic ballast (fluorescent or HMI) into a portable generator. In this case, the impedance of the power generating system (generator and distribution cable) is sufficient enough that a harmonic current will induce a voltage at the same frequency. For example, a 5th harmonic current will produce a 5th harmonic voltage, a 7th harmonic current will produce a 7th harmonic voltage, etc. Since, as we saw above, a distorted current waveform is made up of the fundamental plus one or more harmonics currents, each of these currents flowing through an impedance will, result in voltage harmonics appearing at the load bus, a voltage drop, and distortion of the voltage waveform.

 

Creation_of_Harmonics_Flow.jpeg

Each harmonic current in the electrical distribution system will cause a voltage at the same harmonic to exist when the harmonic current flows into an impedance. [/img]

 

Since electronic ballasts consume current only at the peak of the voltage waveform (to charge the smoothing capacitor), voltage drop due to system impedance occurs only at the peak of the voltage waveform. In this fashion, the pulsed current consumed by electronic ballasts produces voltage distortion in the form of flat-topping of the voltage waveform.

 

CFL_FlatTop_Waveform.jpg

The pulsed current consumed by electronic ballasts produce voltage distortion in the form of flat- topping.

 

For example, the power waveform above (from my article) is typical of what results from the operation of a 2500W load consisting of non-Power Factor Corrected electronic Kino & HMI ballasts on a conventional portable generator (a Honda EX5500 with a Barber Coleman Governor.) Since the voltage waveform distortion exhibited here can adversely effect other equipment operating on the same power, the generation of harmonic currents by electronic HMI & Fluorescent ballasts should be eliminated whenever possible.

 

Where I am just about out of space, I will pick up with how Isabelle could mitigate the problems caused by harmonic currents and make her CFL balloon light work in my next post.

 

Guy Holt, Gaffer, ScreenLight & Grip, Boston

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Guy, without getting into too much technical info, It'll flicker because I've observed them flicker before both on mains and Genny power on an SR3 @180, an EX1 @180 and a 2M @150 shutters respectively. Now, will all of them flicker, probably not, and I am sure there are brands which do no flicker. But point being that Temperature and voltage getting to 'em (over and under) seems to producer flicker results on the camera. It's visible on monitors for video in my experience, for film, though can be a bit of a pain. I can only speak from my own experience with CFL bulbs, which is both good and bad (i had an awesome 300w CFL bulb that was flicker free no matter what I threw at it, and I've had bad experiences with others. Hit or miss and something to test if you want to try it out).

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Since the voltage waveform distortion exhibited in my post above can adversely effect other equipment operating on the same power, the generation of harmonic currents by electronic HMI & Fluorescent ballasts should be eliminated whenever possible. Otherwise they can build to a point where they will have a disastrous effect upon other equipment. As more and more electronic components, like lap top computers, hard drives, and HD monitors, which are themselves sources of harmonic distortion (but of a lower amplitude than solid state lighting ballasts) are integrated into the typical location production package, harmonic currents begin to combine with unpredictable consequences. In fact, a viscous cycle can get started. The more harmonic orders that are generated, the more distorted the power supplied by the generator becomes. The more distorted the power waveform becomes, the more harmonic currents are thrown back into the electrical distribution system, which in turn, creates additional voltage distortion. In this fashion, something akin to a feedback loop can get started. Very often, the operation of electrical equipment may seem normal, but under a certain combination of conditions, the impact of harmonics is enhanced with unpredictable results.

 

makeup_squarewave_alt.gif

Sprectrum analysis of the high frequency Harmonic Currents that induce a flat-topped a voltage waveform at the load bus.

 

The severe voltage waveform distortion exhibited above can cause overheating and failing equipment, efficiency losses, circuit breaker trips, and instability of the generator's voltage and frequency. In addition to creating the radio frequency interference (RFI) mentioned on the Lowell Light website, Harmonic noise of this magnitude can also cause component level damage to HD digital cinema production equipment and create ground loops. Harmonics can also cause excessive current on the distribution system neutral (see below.) And, since the neutral conductor of a distribution system is not fused, it can cause the neutral to overheat and possibly catch fire.

 

High_Nuetral_Return_CFL.jpg

Substituting incandescent lamps with the equivalent wattage of CFLs in a small single phase distribution system substantially increases the current on the system neutral.

 

For this reason, on their website Kino Flo cautions users of their older style fixtures, 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.

 

 

The first step in mitigating the problems caused by harmonic currents is to eliminate the currents. Where customarily the largest source of harmonic currents in a typical lighting package are HMI and Fluorescent lights with electronic ballasts, using only ballasts with power factor correction (PFC) circuitry will go a long way in reducing the number of harmonic currents in the power stream. By simply eliminatng the generation of harmonic currents, a PFC circuit realigns voltage and current and induces a smoother power waveform at the distribution bus. As a result, the ballast uses power more efficiently with minimized return current and line noise and also reduces heat, thereby increasing their reliability (see my post on “How Power Factor Correction Works” for more details.)

 

Effect_of_PFC_in_Flos.jpg

 

The second step in mitigating the problems caused by harmonic currents is to use inverter generators. The combination of the improved power factor of the ballasts and the nearly pure power waveform of inverter generators makes it possible to reliably power larger lights, or more smaller lights, than has been possible before on a small portable gas generator. For example, the power waveform below, is the same 2500W load but with power factor correction operating on our modified Honda EU6500is Inverter Generator. As you can see, the difference between the resulting waveforms is startling. Even though the load is the same, the fact that it is power factor corrected, and the power is being generated by an inverter generator, results in virtually no power waveform distortion. For this reason, sensitive electronic production equipment will operate reliably and without damage on the same power. And, the generator is capable of operating larger, or more smaller, lights than has ever been possible before on a portable gas generator.

 

waveform_Inv_PFC_kino.jpg

The nearly pure voltage waveform of Power Factor Corrected ballasts operating on an inverter generator. Note: No Flat Topping

 

The extremely low line noise exhibited in the inverter generator power waveform above creates a new math when it comes to calculating the lighting load you can put on a portable generator. Where before you could not operate more than a couple 1200W HMIs with non-PFC ballasts on a conventional generator because of the consequent harmonic distortion, now 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.

 

According to this new math, when you add up the incremental savings in power to be gained by using only PFC HMI ballasts, add to it energy efficient sources like the Kino Flo ParaBeam fixtures (which are also PFC), and combine it with the pure waveform of inverter generators, you can run more HMI and Flo lights on a portable gas generator than has been possible before. For example, the 7500W capacity of our modified Honda EU6500is Inverter Generator can power a lighting package that consists of a PFC 2.5kw HMI Par, PFC 1200, & 800 HMI Pars, a couple of Kino Flo ParaBeam 400s, a couple of ParaBeam 200s, and a Flat Head 80. Given the light sensitivity of HD cameras, this is pretty much all the light you will need for a low budget HDV production. Use this

link for more information about the benefits of low line noise.

 

Unfortunately for Isabelle, according the table at top, power factor correction is only available in the high voltage versions of these 200watt 8u CFL bulbs. So her best bet is to use an inverter generator when she needs to power her lantern on locations without grid power.

 

If you still don’t entirely understand how power factor correction works in electronic HMI ballasts, 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, is a more detailed explanation of the basic electrical engineering principles behind harmonic distortion and how it can adversely effect generators. The article is available on our website.

 

Guy Holt, Gaffer, ScreenLight & Grip, Boston

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Guy, without getting into too much technical info, It'll flicker because I've observed them flicker before both on mains and Genny power .... point being that Temperature and voltage getting to 'em (over and under) seems to producer flicker results on the camera.

 

If you observed the flicker on both mains and Genny power than it probably does not have to do with erratic voltage supplied by a generator. To get technical, what you probably experienced is a type of flicker problem called an “eratz ripple.” Even though the bulbs of CFLs operate at high-frequency, the cycles can stack 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 using CFLs in fluorescent soft banks or using solid-state high frequency fluorescent ballasts for built-in set practical light fixtures, it is necessary to shoot tests with the CFL or ballast you plan to use to make sure you will not get an “eratz ripple.”

 

Guy Holt, Gaffer, ScreenLight & Grip, Boston

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