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Isabelle Landers
03-05-2010, 06:31 AM
I've thought about the daylight CFL idea though for putting into Chinese Lanterns for a soft moonlight effect outside at night.

This post by David Mullen in another thread (http://reduser.net/forum/showthread.php?p=562618#post562618) gave 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/uploadedimages/products/2/9/B476534-20070423031229.jpg

http://www.inspironphoto.com/index.php?main_page=popup_image&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 as well. Granted they won't float like a helium balloon, but I could fly it with a 20' menace arm or suspend it with aircraft cable between two trees. Does anyone see any reason this setup wouldn't work?

- Isabelle Landers, Gaffer, Nashua, NH

Erik Bien
03-05-2010, 06:56 AM
Does anyone see any reason this setup wouldn't work?

The softbox head has closely-spaced medium-base (E27) sockets, but the 200W CFLs are mogul base (E39) and about 5 inches in diameter — they won't fit.

Isabelle Landers
03-05-2010, 06:44 PM
they won't fit.

That would be a problem. I guess I could make up my own fixture from outdoor lighting parts available at Home Depot. I saw Jack English use a similar set up when they were shooting "The Great Debaters" at Harvard University. It was a large (48") lantern with three mogul base 1500W DSF Quartz Halogen bulbs in it. Where their fixture was wired with a 60A Bates plug, I could wire mine with a 20A U-ground Edison plug because the nine 200W CFLs bulbs will pull around 15 amps total. It will produce the tungsten equivalent of a 7650W Tungsten balloon and I can plug it into a standard household circuit. Does anyone see any other reasons this setup wouldn't work?

- Isabelle Landers, Gaffer, Nashua, NH

Richard Andrewski
03-05-2010, 08:53 PM
With the balloon light you have one or more very concentrated point light (HMI) sources inside the diffusion of the balloon. These will have an even better throw than tungsten would. Thus they will light the surface of the ball better than the CFLs would and give more output.

In what you want to do, you are taking something that is already a very soft and diffused large source and putting it inside another diffusor. While I like the 200w bulb, and we sell it in 2 different color temperatures, I definitely wouldn't see it as a replacement for an hmi used in a balloon. I would be more likely to run a fixture with multiple 200w mogul CFL bulbs outside of any other diffusion and use it like that.

Noah Kadner
03-05-2010, 09:15 PM
They're not that expensive as a rental- especially when you realize the sorts of lighting they can take the place of.

Noah

Justin McAleece
03-05-2010, 11:34 PM
sounds like a great idea but yeah they don't need much more diffusion, they are already pretty soft without much throw. On a similar tangent, I have like 400 24w CFL bulbs and I wanted to make a poor man's wall o lite out of them on one big flat board of some sort. Does anyone know of somewhere I could buy a grid of sockets like something with 6*10 sockets on it. I just don't want to have to buy them all individually and screw them in and wire them and everything. I have been looking around but can't find anything like that. Anyone with any ideas?

Isabelle Landers
03-06-2010, 06:49 AM
They're not that expensive as a rental- especially when you realize the sorts of lighting they can take the place of.


Keep in mind I'm posting from southern New Hampshire. The closest rental houses are in Boston and none of them have Balloon lights. We have to go to NYC for them which adds considerably to the expense. And while HMI globes would be the ideal source for a balloon, they take it out or the realm of DIY (do-it-yourself.) I am confident I can wire mogul base sockets into a exterior lighting electrical box.Besides, HMI would make it too expensive to make and power. A CFL balloon would also have the ability to be lamped daylight or tungsten, and run on a standard house circuit. You all are right that the paper lantern may be unnecessary and redundant, but it would make a single coherent source out of the nine globes. So it sounds like there is not real reason this shouldn't work.

Isabelle Landers, Gaffer, Nashua, NH.

Guy Bryan Holt
03-06-2010, 11:43 AM
I am confident I can wire mogul base sockets into a exterior lighting electrical box. … A CFL balloon would also have the ability to …. run on a standard house circuit. ..... So it sounds like there is not real reason this shouldn't work.

You can make this work, but not how you envision it. First off, 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 single household circuit, you will likely overheat the neutral in the light if you don’t beef it up, 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 as she envisions it 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 (http://www.screenlightandgrip.com/html/emailnewsletter_generators.html) at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

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 Isabelle calculated a 200W bulb should draw using Ohm’s Law (W=VxA), is the difference between what is called “Apparent Power” and “True Power.”


http://www.screenlightandgrip.com/images/generators/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.)


http://www.screenlightandgrip.com/images/generators/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 milli-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.


http://www.screenlightandgrip.com/images/generators/CFL_Waveform.jpg
Current and Voltage Waveform of a Brelight 25W CFL Bulb

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.


http://www.screenlightandgrip.com/images/generators/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.


http://www.screenlightandgrip.com/images/generators/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.

Where I am just about out of space, I will pick up with how the diode-capacitor section of fluorescent and HMI electronic ballast generates harmonics in my next post.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com), Boston

Guy Bryan Holt
03-06-2010, 11:44 AM
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.

As shown in the illustration below, 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.


http://www.screenlightandgrip.com/images/generators/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.)

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 in the previous post) 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 carry 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 diode-capacitor 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.)


http://www.screenlightandgrip.com/images/generators/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 saw in the oscilloscope shot in the previous post, 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.)


http://www.screenlightandgrip.com/images/generators/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.


http://www.screenlightandgrip.com/images/generators/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.

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.


http://www.screenlightandgrip.com/images/generators/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 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.) It is also a good indication of what would likely result from operating Isabelle’s CFL Balloon along with several small HMIs on a conventional putt-putt generator. 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 (http://www.screenlightandgrip.com), Boston

Guy Bryan Holt
03-06-2010, 11:48 AM
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.


http://www.screenlightandgrip.com/images/generators/makeup_squarewave_alt.gif
Sprectrum analysis of the high frequency Harmonic Currents that induce a flat-topped 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.


http://www.screenlightandgrip.com/images/generators/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” (http://www.kinoflo.com/FYI/FAQs.htm#2).) 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 (http://www.screenlightandgrip.com/html/emailnewsletter_generators.html) at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

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 eliminating 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” (http://reduser.net/forum/showthread.php?t=40275) for more details.)


http://www.screenlightandgrip.com/images/generators/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.


http://www.screenlightandgrip.com/images/generators/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 ( http://www.screenlightandgrip.com/html/emailnewsletter_generators.html) - http://www.screenlightandgrip.com/html/emailnewsletter_generators.html - for more information about the benefits of low line noise.

Unfortunately for Isabelle, according the table at the outset, power factor correction is only available in the high voltage versions of these 200watt 8u CFL bulbs. So her best bet is to beef up the neutral in her CFL head so that it doesn’t overheat; split the load of the bulbs over two Edison plug ends that she can plug into separate circuits; and use an inverter generator when she needs to power her lantern on locations without grid power. If she takes these precautions she should have no problem.

If you still don’t entirely understand power factor and how it relates to the operation of electronic HMI and Fluorescent ballasts on generators, 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 (http://www.screenlightandgrip.com/html/emailnewsletter_generators.html) at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com), Boston

Mark Collins
03-07-2010, 11:28 AM
They're not that expensive as a rental- especially when you realize the sorts of lighting they can take the place of.

Noah

Agreed. Though I prefer lanterns to balloons, even on a small budget they aren't exceptionally pricey.

Stephen Pruitt
03-07-2010, 10:52 PM
That's got to be a typo on the MaxLite table, Guy, as the other two bulbs both follow Ohm's law almost perfectly.

On the other hand, it's ridiculous to try fly them overhead inside a China ball. They have virtually no throw at all (being so incredibly soft) and definitely will lose a ton of lumens once they are put inside anything.

Stephen

Guy Bryan Holt
03-08-2010, 09:06 AM
That's got to be a typo on the MaxLite table, Guy, as the other two bulbs both follow Ohm's law almost perfectly.

It’s not a typo. If you look at the table of harmonic distortion by type of fluorescent I have reposted below you will see that CFLs are categorically the worst offenders with a Total Harmonic Distortion (THD) over 100%.


http://www.screenlightandgrip.com/images/generators/Table_THD_Flo_Ballasts.jpg

Where most distributors of CFLs for motion picture lighting hide that specification, Lowel Light on their website does warn that their compact fluorescent (CFL) bulb, the Lowel Ego,“… may cause interference with radios, cordless phones, televisions, and remote controls.”(http://www.lowel.com/ego/lamp_info.html) which is a sure indication that it creates severe harmonic currents and has a poor power factor.

The reason that the higher voltage Maxlite 8cu 200 W CFL bulbs are Power Factor Corrected is because they are manufactured for the 230V European market. The EU requires that any electrical appliance over 75W incorporate Power Factor Correction (PFC) circuits. Where PFC circuits add considerably to the cost of a fixture, manufacturers generally do not include it in their products intended for the 120V North American market where it is not mandated.

While it is true that all major manufacturers of HMI ballasts include PFC circuitry in HMIs in the 6-18kw range - they do so by necessity. The early line of Lightmaker electronic ballasts (some of which are still kicking around ebay) proved that PFC circuitry was absolutely necessary in large ballasts to reduce heat and returns on the neutral, and to increase ballast reliability. Because of the added cost, weight, and complexity of PFC circuitry, ballast manufacturers in the US have offered PFC circuitry only 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.)

Another reason PFC circuitry has not been offered in smaller HMI ballasts 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 – I think you would have to agree that is a major boost in production capability and pertinent to any one using a portable generator as their principle source of set power.

But that is not the only benefit to using PFC electronic ballasts (both HMI & fluorescent) on 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. 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 HMI & fluorescent 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 and fluorescents 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 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.

Except for one notable exception, when manufacturers do offer PFC circuitry in smaller HMI ballasts it is at a premium, adding as much as a $1000 to the cost of a 1200W ballast for instance. The new ballast manufacturer Power-2-Light, on the other hand, is including PFC circuitry in their ballasts at the same price point as other manufacturer’s non-PFC ballasts. But where Power-2- Light is still very new to the market, it is still the case that almost every 575/1200 W ballast that you will find in a rental house in North America will be a non-PFC electronic ballast.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com"), Boston

Guy Bryan Holt
03-08-2010, 09:32 AM
On the other hand, it's ridiculous to try fly them overhead inside a China ball. They have virtually no throw at all (being so incredibly soft) and definitely will lose a ton of lumens once they are put inside anything.

While it might seem ridiculous to you to put a soft globe like a 200W 8cu CFL in a lantern, I believe Isabelle was inspired by a custom fixture used by Jack English on the “Great Debaters.”


I saw Jack English use a similar set up when they were shooting "The Great Debaters" at Harvard University. It was a large (48") lantern with three mogul base 1500W DSF Quartz Halogen bulbs in it.

The DSF globes were originally used in scoop lights and they too are incredibly soft and have virtually no throw. Yet Jack English, the gaffer of over 50 major features (including such films as the new “Sherlock Holmes”, “The Day the Earth Stood Still “, and “The Women”) thought it a good idea to put them in a lantern too. I wouldn’t disparage Isabelle’s idea – if designed and used properly she might have something usefull.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com"), Boston

Isabelle Landers
03-13-2010, 09:10 AM
I wouldn’t disparage Isabelle’s idea – if designed and used properly she might have something usefull.

Thanks for the encouragement and support. I've learned alot from your posts and will definitely follow your suggestions. I will report back when I have had a chance to try out this idea.

Thanks Again, Isabelle Landers, Gaffer, Nashua, NH

Tim Duran
04-30-2010, 09:29 PM
Guy, yes, you're a bit verbose, but lots of good information. Thanks for taking the time to continue to educate us on what many people forget about.

Q: how does the more frequent use of LED lights, and now with individual 3 watt bulbs, affect other equipment on the set from your experience? Please keep your answer to less than 50,000 words.

Jim Hoffman
04-30-2010, 11:47 PM
You rock Guy.

rod bradley
05-01-2010, 12:10 AM
Indeed, you do rock -- and I, for one, salute your attention to detail and lucidity -- in which some may find a certain elegant verbosity. Long live yours! And thanks for your generosity!

Charles Angus
05-01-2010, 02:40 AM
Off topic part of post:

In the words of forum readers everywhere, Guy, TLDR - too long, didn't read.

As I (and, I'm sure, others) have said - put this stuff on a bloody webpage, and post a SINGLE LINK to it on the forum. Interested people will read it, and you won't fill up a perfectly good thread with colossal blocks of text.

Sorry to the thread for getting off-topic.

On topic part of post:

My question would be why only 48"? If I was building something like this, I feel like I would want a bigger source than that.

Test your CFL's on a household circuit - I bet it would work. Despite Guy's research on the matter, I have never had problems running a flicker-free 1.2k HMI off of 15A circuits (even with some other small draws on the same circuit) despite the fact that he claims it would draw 19A. I don't have as much experience with CFL's, but I would bet the problem is not as severe as Guy indicates. (Sorry Guy, just my opinion. And while I didn't read this particular post of yours, I have read the page on your site, and your posts on CML, both of which I believe cover pretty much the same ground.)

I'm also wondering about how low you could get the weight, and if it would be crazy to fly it with external helium balloons...

If you take any further steps in this direction, I would love to hear about!

Joe G.
05-01-2010, 04:19 PM
It occurs to me that a big parabolic shaped plastic bowl would be useful. Something like 3, 4 or 5 feet across. Then spray the inside silver and mount a few of those big CFLs inside. The shape of the bowl would help throw the light where you want it.

Of course it won't fly without some sort of UFO technology. But you could mount it to a high structure.

Blair S. Paulsen
05-01-2010, 06:48 PM
I cast my vote for posts like Guy's as they are full of valuable information, particularly on a thread where the topic is DIY lighting gotchas. My theory is, only people who are interested in building such rigs are even on this thread and could easily overlook many of the issues described in Guy's posts.

Cheers - #19

Guy Bryan Holt
05-03-2010, 10:48 AM
Test your CFL's on a household circuit - I bet it would work. I don't have as much experience with CFL's, but I would bet the problem is not as severe as Guy indicates. (Sorry Guy, just my opinion. And while I didn't read this particular post of yours, I have read the page on your site, and your posts on CML, both of which I believe cover pretty much the same ground.

I know you think my post is tediously long. But, I find again and again that because of the brevity of the posts, online forums like this are filled with a lot of miscommunication. Since a little knowledge can be a dangerous thing when it comes to handling electricity (case in point), I felt it necessary to explain briefly (yes that was brief) why Isabelle’s set up as she envisions it will not work and even be hazardous. For a more detailed explanation, I did suggest readers follow a link I provided to an article I wrote for our company newsletter on the use of portable generators in motion picture lighting. In the article, was a more detailed explanation of the basic electrical engineering principles behind power factor. But, of course, you wouldn’t know that because you didn’t read my post, but still felt qualified to comment on its contents.


... I bet it would work. I don't have as much experience..., but I would bet the problem is not as severe ..., just my opinion. ... while I didn't read this particular post of yours ... I believe ....

Your response – “Test your CFL's on a household circuit - I bet it would work” – is precisely the uninformed speculation that is dangerous when it comes to electrical matters (Sorry Charles, just my opinion.) If you had bothered to read my post you would know that the harmonic currents CFLs generate stack on the neutral, and since there is no over-current protection on the neutral, can lead to overloading of the neutral and a fire like the one that occurred in Vice President Dick Cheney's suite of offices in the historic Eisenhower Executive Office Building next to the White House on December 19, 2007. The cause of the fire that started in an electrical closet on the building's second floor was found to be the result of uninformed staff replacing all the incandescent bulbs in the complex with CFLs.

I recently presented on harmonics to the electrical department of IATSE Local 481 as part of the “Advanced Power and Generation for Set Lighting Technicians Seminar” offered by Russ Saunders of Saunders Electric (http://www.saunderselectric.com/) (the provider of power generation services for the Academy Awards since 1952 and a recipient of a technical Emmy). Several licensed electricians in my IATSE Local told me at the seminar that new requirements for wiring buildings as a result of fires started by CFLs is a part of the continuing education they are required to take to maintain their licenses.

But, I detect in your post a note of skepticism regarding my “claims.” If you won’t take my word that the harmonics created by SMPSs can cause excessive current on the distribution system neutral, perhaps you will take Kino Flo’s. 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” (http://www.kinoflo.com/FYI/FAQs.htm#2).)

And if you don’t believe me when I say that CFLs will draw twice their rated load and generate harmonic currents that have a severe adverse effect on the governing systems of generators, perhaps you will believe Lighting Designer Kevan Shaw. In his You-Tube video, “Compact Fluorescent verses the generator,” (http://www.youtube.com/watch?v=LeCqreRMzKM)at http://www.youtube.com/watch?v=LeCqreRMzKM, he compares the effect of equal wattages of CFLs and Incandescent lights on a small portable generator. In his test, he first operates a 575W ETC Source Four Leko with Quartz Halogen bulb on an 850W two stroke gas generator without problem. However, when he tries to operate an equivalent wattage of CFLs (30-18W bulbs) the generator goes berserk. Only after turning off half the CFL Bulbs does the generator operate normally with a remaining load of 15 - 18W CFLs (270 W.) What accounts for the erratic behavior of the generator in this video under a smaller load of CFLs? It is a combination of the poor Power Factor of the CFL bulbs and the harmonic currents they generate.

Even though the 15 CFL bulbs have a True Power of 270W, the Watt indicator on Kevan's generator indicates that they draw twice that in Apparent Power (535W), or have a Power Factor of .5 (270W/535W =.504.) The fact that CFL bulbs consume double the energy (Apparent Power) for the 18 Watts of light (True Power) they generate, is only half the story here. Kevan Shaw’s video also clearly demonstrates the severe effect that leading power factor loads - like CFLs, HMIs, & Fluorescents - can have on the governing systems of conventional AVR generators.


http://www.screenlightandgrip.com/images/generators/CFL_vs_Gen_Dem.jpg

When Kevan turns off the 18W CFL bulbs one at a time until the generator stabilizes, he is not only demonstrating that 15 – 18W CFL bulbs has roughly the same Apparent Power (535W), according to the generator’s Watt meter, as a 575W incandescent light; but, also that the maximum Leading Power Factor load a 850W conventional generator can operate satisfactorily is 270 Watts (15 – 18WCFL bulbs). Looked at from another angle, 576 Watts of Apparent Power with a Leading Power Factor (16 - 18W CFL bulbs) overloaded the generator, while 575 Watts of Apparent Power with a Unity Power Factor (the 575W Quartz Leko) did not. What accounts for this difference? Since the load is almost the same (576 & 575 Watts of Apparent Power respectively), the only factor that can account for the generator going berserk with the equivalent load of CFL lights is the harmonic currents that they generate, that the Quartz Leko does not. Without a doubt, Kevan Shaw’s video is a clear demonstration of the adverse effect that harmonic currents have on the governing systems of conventional AVR generators.

For the same reason that Kevan Shaw was not able to operate more than 270 Watts of CFL bulbs (15–18W bulbs), it has never been possible to reliably operate more than a couple of 1200W HMIs with non-PFC electronic ballasts on 6500W conventional AVR generators. The adverse effects of the harmonic currents they generate, so
graphically demonstrated in Kevan’s video, limits the total amount of Leading Power Factor loads, as compared to Unity Power Factor loads, that can be reliably operated on conventional AVR generators. If a reader of this post still doesn’t entirely understand what I am saying, I would encourage them to read the article I wrote for our company newsletter on the use of portable generators in motion picture lighting before attempting to build their own lights. In it, is a more detailed explanation of the basic electrical engineering principles behind Power Factor, harmonic distortion, and it’s adverse effects on generators. The article is available on our website (http://www.screenlightandgrip.com/html/emailnewsletter_generators.html) at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com/), Boston

Guy Bryan Holt
05-03-2010, 10:51 AM
In the words of forum readers everywhere, Guy, TLDR - too long, didn't read.

You may think my posts verbose, but I am only trying to raise an awareness of the adverse effect that an increase in harmonic noise as a result of a change in lighting technology - the introduction of Switch Mode Power Supplies (SMPS) - is having on set power. But, don't just take my word for it: apparently, harmonics generated by SMPSs is enough of a problem to warrant several sections in the third edition of the "Set Lighting Technician’s Handbook." To quote Harry Box (Page 337 under "Power Problems from Electronic Loads"):

"Much of today's lighting technology relies on electronics such as DC rectifiers (electronic HMI ballasts), silicone-controlled rectifiers (SCRs), capacitors (magnetic & electronic HMI ballasts), and high-frequency switching power supplies (the IGBTs of electronic ballasts). These kinds of load can have undesirable effects on the current waveform, revealing themselves in the form of overheating or failing equipment , efficiency losses, circuit breaker trips, excessive current on the neutral wire, interference and instability with generators, noisy or overheating transformers and service equipment, and even loosened electrical connections. In the following sections, we discuss the power factor and current harmonics and look at their effects. Your awareness of these effects will help you to build systems that avoid or mitigate problems and show how to test for problems.(the parenthesis are mine)"

Now does this sound like harmonics is not a problem. The problem exists. Now you can, either deny it and be worse off for it; or as Harry Box suggests, you can accept it and "your awareness of these effects will help you to build systems that avoid or mitigate problems (on set.)" Which, incidentally is what I try to do in the article I have written for our company newsletter on the use of portable generators in motion picture lighting. (http://www.screenlightandgrip.com/html/emailnewsletter_generators.html)

In the article, I set out to demonstrate that through an awareness of the effects caused by harmonics it is possible to build a system that mitigates the problems they pose. That through a substantial reduction in line noise, as a result of using Power Factor Corrected (PFC) ballasts (both HMI & Fluorescent), it is possible to create a new math when it comes to calculating the load you can put on an electrical circuit or on a portable gas generator. According to this new math, it is possible to maximize the load that you can safely put on a circuit, or the continuous load that can run off of portable generator, by using HMI and Fluorescent lights with Power Factor Corrected (PFC) ballasts.

Where, in the past we had to de-rate portable generators because of the inherent short comings, so graphically depicted in Kevan Shaw’s You-Tube Video, of conventional generators when dealing with the harmonic noise generated by non-PFC electronic ballasts (both HMI & Fluorescent); now an inverter generator can be loaded to capacity with PFC ballasts. 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 Power Factor Corrected Kino Flo Parabeam fixtures, and combine it with the pure waveform of low impedance inverter generators, like the Honda EU6500is, you can run more HMI 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. Where an informed awareness of the effects of harmonics will enable you to operate more HMI & Fluorescent lights on a portable gas generator than has ever been possible before, uninformed speculation only creates a fire hazard.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com/), Boston

Guy Bryan Holt
05-03-2010, 12:53 PM
… I have never had problems running a flicker-free 1.2k HMI off of 15A circuits (even with some other small draws on the same circuit) despite the fact that he claims it would draw 19A.

That may be because it is harder to know the amperage of the circuit that you are plugged into than it is to know the amperage of the light you are plugging in. To know the amperage of the circuit with any confidence you have to methodically trace it by shutting of breakers to isolate the outlet in question or use a live wire tracer. Unless you take the time to trace it you can never be certain of the amperage of the circuit you are plugged into. Whereas, to find the amperage of the light you are plugging in all you have to do is look at the manufacturer’s nameplate on the back of the ballast.


http://www.screenlightandgrip.com/images/generators/ArriEBL1200_Ballast_Nameplate.jpg


Above is the nameplate from an Arri 575/1200 Electronic Ballast with DMX Control. You can see that it is clearly marked that it will draw 18A of current ("I") at 125 Volts ("U"). According to my math that works out to be roughly 19A at 120V. You will also notice that it states that the ballast has a cos@=.6 which mean that the Power Factor is .6. Given how easy it is to determine how much power this ballast will draw, if I had to speculate, I would bet that you were plugged into a 20A circuit.

Guy Holt, Gaffer, ScreenLight & Grip (http://www.screenlightandgrip.com/), Boston

Isabelle Landers
05-08-2010, 10:28 AM
You can make this work...
The electronic ballasts of self ballasted CFLs, ... 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.

This gave me the idea to use CFLs as practical bulbs for high speed work, but raised some questions that I have yet been able to get answered. I’m gaffing an upcoming realty show that uses a lot of high-speed cinematography. They shoot with the Red at 600 FPS and the Phantom at 1000FPS. They want to use of practical fixtures (table lamps, floor lamps, etc.) on the set for the first time and I am not certain how to approach it. I am looking for suggestions on how to treat the practicals so that they look realistic.

I find that practical lamps never look convincing unless one treats the lampshade as well as boost the bulb wattage. I find that after stopping down to keep the shade from burning out that the output of the practical, on the table it sits on or the wall its on, looks rather anemic. Years ago Walter Lassally, BSC, instructed me to balance practicals such that an incident reading of the direct output one foot away from the bulb is one stop over exposure. I have found that rule of thumb gives a realistic output to the practical - the light emitted downward onto the table top and upward onto the wall or ceiling is realistic - but it usually requires lining the inside of the shade with ND9 so that the shade does not become too hot.

To follow that same rule of thumb for high speed would then require practical bulbs of considerably higher wattage than 211, 212, or 213. Without larger practical bulbs, the output of practical fixtures is nullified by the light levels required for high speed which usually requires 5Ks, 10Ks, and even 20Ks. The use of multiple high CRI Compact Fluorescent bulbs in a practical lamp if the shade provides sufficient space was discussed as a possible solution in a CML thread on this same topic. But no one on CML had any practical experience (excuse the pun) using CFLs in high speed cinematography to say if they will flicker.

Lowel states on their website that “our 80 Watt daylight fluorescent lamps (provide) high output with accurate color. Its high frequency ballast is designed for flicker-free hi-res digital still, video, and slow-motion cinema use.” And, according to Guy’s posts here the screw base CFL bulbs contain tiny electronic ballasts that apply high frequency output, around 40 kHz or higher, to the lamp tube which means that they may very well be flicker-free at 1000fps. At those frequencies the period of time between the off and on pulse of each cycle is so short that the illuminating phosphors in the lamp tube may not decay in light output enough to cause a flicker. Like the 'thermal inertia’ of tungsten bulbs - metal glowing white hot - that keeps them emitting light for a short time after the power drops off, the phosphors continue to glow after the power drops off as it switches at high frequency making them possibly flicker free.

Lowel and others provide CFL bulbs with screw bases in both 3200 and 5500 Kelvin with a CRI of 90+. Where a 80W CFL has the equivalent output of a 400W tungsten bulb, three of them in the shade of a large table lamp will give the equivalent of 1200Watts of tungsten light – which just might be enough to read at high speed – yet not melt the shade because they generate very little heat. Of course as Guy has pointed out, the lamp will have to be rewired to accommodate the poor power factor of CFL bulbs. Has anyone tried using CFLs in high speed and know if they will flicker?

Isabelle Landers, Gaffer, Nashua, NH

David Mullen ASC
05-08-2010, 11:32 AM
1000 fps is something over 5-stops of light loss, not sure how a table lamp is going to read realistically bright, but in terms of the filament flicker issue, I don't know what the solution would be.

Eileen Ryan
05-17-2010, 06:07 AM
Has anyone tried using CFLs in high speed and know if they will flicker?

I have successfully used smaller tungsten fixtures (1ks & 2ks) as kickers or backlights for high speed by using three heads together and pluging each head into a separate phase of the distro. This way the rise and fall in the output of individual heads is averaged out to a continuous output between the three heads. I wonder if the same approach would work with CFLs. If the rise and fall in the output of the phosphors of individual CFL bulbs will be averaged out between bulbs in a single practical. If that were the case, you could rewire the practical fixture so that each bulb had it’s own plug end? That way you could plug each bulb into a separate leg of the distro.

Eileen Ryan, Gaffer, Boston