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The role of L.E.D lighting in filmmaking

L.E.D lighting lighting sharing your experience sensors lighting efficiency CRI

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#1 Aaron Takhar

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Posted 07 March 2015 - 06:08 AM

Hi all,

 

I am currently in the process of writing my University dissertation which is a comparative study between L.E.D lighting against traditional lighting fixtures in Hollywood film-making (such as Tungsten Halogen lighting fixtures) and was wondering if anyone could help me answer some questions on the subject.

 

How far a role does colour rendering index play in D.O.P’s choosing Tungsten Halogen lights over L.E.D?

With improved sensors able to operate in less light will this be advantageous for less powerful LED lights.

Is there still a need in film-making (especially Hollywood film-making) for the bigger lighting fixtures? (e.g lighting fixtures such as the Sunray 24K Fresnel light)

 

 

Thank you very much for your time. 


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#2 Chris D Walker

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Posted 07 March 2015 - 10:19 AM

One problem with LEDs is different manufacturers will have varying processes such as the number of diodes, the binning process applied, and the phosphors used to produce 'white light' that they will not match. A tungsten light from Mole will match with a tungsten light from Arri. DPs have to test for the quality of an LED and whether it is a satisfactory match with other light sources.

 

Big lights won't disappear from large budget films. Productions are not only shooting in low light scenarios; you need big units to fight against natural daylight or for long throw on a large scale set. I can think of maybe two LED lights powerful enough to match the intensity of 6K HMI and they're very expensive to rent. I can rent a kit of three blondes for the same price as a 1x1 Litepanel.

 

LEDs have vastly improved, but they have yet to fulfill the requirements and variety that tungsten lights have in size, punch and accuracy.

 

This might be of interest, too: http://www.newsshoot...rising-answers/


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#3 Tyler Purcell

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Posted 07 March 2015 - 01:52 PM

Yea, I agree with Chris. I still vastly prefer tungsten and florescent (kino's) over LED. I recently did a shoot with a new panel which has three colors and allows you to adjust the color temp so all the panels in your shot are the same color balance. It was a cool idea, it worked OK, but the amount of light they produced was only highlighting what already existed from my tungsten overhead sources. Even though we used a meter which helped match the colors, you could tell the shots were lit by LED's, even though they were on the warm side of the spectrum, they still felt cold for some reason. 

 

These are the reasons I haven't invested in LED's yet. I have a huge tungsten light kit I carry everywhere with me and I'd love to have a nice soft bag that carries 4 - 6 panels of LED. However, they just aren't bright enough and the color balance issue is a huge problem for most stuff. 


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#4 John E Clark

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Posted 07 March 2015 - 04:00 PM

I recently did a shoot with a new panel which has three colors and allows you to adjust the color temp so all the panels in your shot are the same color balance. It was a cool idea, it worked OK, but the amount of light they produced was only highlighting what already existed from my tungsten overhead sources. Even though we used a meter which helped match the colors, you could tell the shots were lit by LED's, even though they were on the warm side of the spectrum, they still felt cold for some reason. 

 

The color meter you used, did it display a spectrum, or just a number? The thought that occurs to me is that one could perhaps have the same number for different spectral components. Like a 'blue' spike may average out with a greater amount of 'red', but when used on something 'white' still give a blue cast...

 

Since I don't have any type of 'color' meter, I can't play around with what a 'meter' would read vs the spectrum produced by various settings, to see if such a conjecture has any truth value.


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#5 Tyler Purcell

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Posted 07 March 2015 - 05:07 PM

We used an earlier/older version of the C700 which allows you to set a target range and shows you how far off you are from that. It's a pretty cool tool to have when you care about color temp. The other camera operator happened to have it, that's the only reason I used it. Normally I don't even carry a meter with me because the spot meter in the blackmagic camera has a histogram and I just pan around the room to get a sense of things before shooting. When shooting film I always carry a spot/ambient meter like the 758. 


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#6 Aaron Takhar

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Posted 08 March 2015 - 08:55 AM

Thanks guys for your helpful comments on the subject matter. I was also wondering if you could offer your expertise on some additional questions I have contemplated?

 

 

Does the portability and energy efficiency of L.E.D lights make them worth selecting over Tungsten Halogen lights for this aspect?

 

How far are L.E.D lights from becoming a dominant technology both in high and low budget filmmaking?

 

Is the possible transition from Tungsten Halogen to L.E.D comparable to the transition from Brute (Carbon Arc Lamps) to Incandescent?

 

How far has technology such as Gamma Correction in post-production and accessories with such as Creamsync gone towards eradicating problems such as flickering and the green spike associated with L.E.D lights?    

 

Is this argument coming too soon in the world of film and media lighting?

 

Thank you very much for your time


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#7 John Miguel King

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Posted 08 March 2015 - 09:35 AM

LEDs are already quite important.

 

The industry embraced Celeb Flos immediately, and luminaires such as Rosco litepads & litepanels have no real competition on multiple situations. Choosing, say, a 2 foot kino over a celeb 200 makes no sense at all. Kinos can't be dimmed, and changing colour requires gels and/or the switching of bulbs. The celeb has a similar CRI, is fully dmx controllable and way easier to shape and control.

 

Likewise, a kit such as Rosco's gaffer kit litepads allows rigging a whole car interior running of one Anton Bauer dionic. ONE.

 

Another great luminaire is the Rotolight. Whenever I'm on exteriors and I want to keep it light I order a couple of them. One dionic will last for half a day of filming, and the punch is pretty amazing. Plus colour temp can be dialed, even from a phone!

 

Now, when it comes to big punchy luminaries, such as pars and fresnells, we're still a long way off. But for soft sources the change is happening now, and it's surprisingly fast.


Edited by John Miguel King, 08 March 2015 - 09:36 AM.

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#8 Chris D Walker

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Posted 08 March 2015 - 10:10 AM

It's not only the green or magenta spike DPs need to be concerned with. If you shoot a Macbeth colour chart with several LED sources there is an unpredictability in which lights will affect which colours. AMPAS did a test with a model wearing a dress with detailed hues of blue, violet and cyan under different sources where an LED didn't have the full spectrum to accurately reproduce the colour, so appeared as merely a blue dress without the fine gradations present in a tungsten-lit scene. Some LEDs can reproduce colour with fidelity but testing is needed to be sure. You can't trust manufacturers measurements of CRI.

 

LED lighting is taking over in lower budget, independent filmmaking because of their efficiency and small size. They can be great for augmentation in smaller spaces.

 

I don't know whether this practice still exists but productions shooting on a stage payed for the space and the number of days being used, not the electricity they were drawing from the stage tie-in. For this reason productions weren't concerned with the efficiency of their lights because they weren't paying the bill.

 

Carbon arcs were loud, DC, and had a short life; we're talking 30 minutes. Incandescent was quiet, AC, and had a much longer life. It made sense for studios to make the switch on stage, although carbon arcs did see use on exteriors until the 80's when HMIs were introduced on a larger scale.


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#9 John Miguel King

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Posted 08 March 2015 - 10:31 AM

Chris, there is a big difference between cheap LEDs and actual, branded, professional quality LEDs. The later have become standard issue in all productions, mostly in the higher end of the spectrum. I've seen them in big brand commercials, prestige BBC dramas and features that most definitely qualify as big budget in UK terms. I've seen them on location, on exteriors and on sound stages.

I have yet to hear anything other than "this is amazing!" on such sets. Very often they aren't even replacing previous technologies. They allow for setups that are essentially impossible with any other technology.

I don't know what you mean by "gamma correction", Aaron?. You mean colour correction? Gamma belongs to a totally different conversation. ;)


Edited by John Miguel King, 08 March 2015 - 10:33 AM.

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#10 Guy Holt

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Posted 08 March 2015 - 10:46 AM



These are the reasons I haven't invested in LED's yet. I have a huge tungsten light kit I carry everywhere with me and I'd love to have a nice soft bag that carries 4 - 6 panels of LED. However, they just aren't bright enough and the color balance issue is a huge problem for most stuff. 

 


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. Where 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.

 

 

LED_CC_34CTO_Day_Conv.jpg

 

 

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.)

 

 

 

LED_CC_34CTO_LED_Conv.jpg

 

 

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


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#11 Guy Holt

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Posted 08 March 2015 - 11:02 AM

Hi all,

I am currently in the process of writing my University dissertation which is a comparative study between L.E.D lighting against traditional lighting fixtures in Hollywood film-making (such as Tungsten Halogen lighting fixtures) and was wondering if anyone could help me answer some questions on the subject.

 

For a  accurate assessment of the color rendering capability of LED fixtures see The Academy of Motion Picture Arts and Sciences'  “Solid State Lighting  Technical Assessment" - a research project in which they systematically tested and compared  the LED technology available  at the time to Incandescent and HMI light sources. On their website they have posted not only side by side comparisons of chip charts exposed under each light source but also set pieces, wardrobe, and make-up. To maintain neutrality, no brand names are mentioned in their results, but they chose lights that reflect the various approaches taken by the major manufacturers of LED fixtures for motion picture applications. You can find a link to the Academy of Motion Picture Arts and Sciences’ “Solid State Lighting Project Technical Assessment", as well as other information regarding LEDS on our website at http://www.screenlig...enerators.html.

 

-       Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental & Sales in Boston


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#12 Aaron Takhar

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Posted 21 March 2015 - 07:37 AM

Sorry John Miguel King, 

 

What excatly do you mean by: "They (L.E.D's) allow for setups that are essentially impossible with any other technology". Do you specfically mean beause of their maluable size and excellent portability?

 

Thanks, Aaron.  


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#13 Adrian Sierkowski

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Posted 21 March 2015 - 10:23 AM

I know LEDs of many stripes have allowed me to do things I normally wouldn't be able to do. They can make life easier; and it is because of size and power plus that some of them you can custom cut and fit into places. I have recently come around to enjoying the LiteRibbons a bit. However, that said, I almost always choose LEDs just for those special instances where they make sense and never as the primary light in a project specifically because of their odd color renditions [unless the project allows for such oddities]


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#14 Guy Holt

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Posted 29 March 2015 - 08:07 PM

How far has technology such as Gamma Correction in post-production and accessories with such as Creamsync gone towards eradicating problems such as flickering and the green spike associated with L.E.D lights?    

 

While you can white balance out/time out the magenta or green bias of LED fixtures in digital video cameras/digital film intermediate, the camera/timer is not able to replace the parts of the spectrum that are missing from LEDs all together. And since gels only rebalance the spectral distribution of a light source by passing the wavelength of the color that they are, gels cannot correct for these deficiencies either because there is not much light of those wavelengths to pass in LEDs to begin with.

 

 

LED_Model_Comp.jpg

                                Left: Tungsten source, Right: White Phosphor LED source.

 

This inability of most LEDs to render color accurately is very visible in the tests performed by The Academy of Motion Picture Arts and Sciences (AMPAS) as part of their “Solid State Lighting Project Technical Assessment” I mentioned previously  (see http://www.screenlig... Output AC LEDs 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 White Phosphor LED source. The tungsten-lit footage displayed all of the subtle differences in blue tones in the fabric, while the LED-lit footage, lacking cyan output, showed just a nice blue dress, without the same richness of hue. Since the light doesn’t put out much cyan, the camera/film simply can’t record it.

 

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 (remote phosphor included) because of the steep drop off of high frequency colors (above the 600nm cut off) such as pinks, reds, oranges, and other long wave-length colors. As the illustration below, comparing the reflected spectral distribution of a Caucasian skin tone under theoretical pure white light (an even distribution of all wavelengths) to that of a Phosphor White LED demonstrates, absent these wavelengths the skin tones look pale under LEDs because light reflected by the skin tone is likewise absent these critical long wavelength colors.

 

 

LED_Effect_on_Skin_Color.jpg

                         Reflected Spectral Distribution of Caucasian skin tone under theoretical White Light and Phosphor White LED Light

 

 

In the picture above illuminated by the Phosphor White LED, both the cyan/blue dress and the skin tone, don’t reproduce well because you can't get accurate color reflected from an object unless that color is in the light in the first place. In other words, if the light source doesn’t generate the color (cyan), it is not reflected by the object (the dress) and so the camera/film simply can’t record it.  And, as Cinematographer Daryn Okada, ASC, discovered the hard way in an experience he recounts in the ICG Magazine (http://www.icgmagazine.com/wordpress/2011/06/02/it’s-a-phosphorous-world/), color gel packs, camera white balance, or digital intermediate timing can’t bring it out if it isn’t there to begin with.

 

Like many ASC cinematographer, Daryn Okada only uses LEDs as “touch up” lights to add a little something where key lights don’t cover. After a recent experience, he doesn’t use LEDs even for that limited purpose. Needing to touch up a face on one talent mark,  he hid a small LED unit behind a chair, to add some glow to an actress’s face when she reached a mark where the keys had fallen off. “The manufacturer claimed the unit to be a ‘tungsten LED source’” he recounts. “She stopped right in the doorway, where I had this LED, and looked fine. But when I got the dailies back, her face was totally magenta.” What’s worse, Okada says the image could not be repaired in post, because there wasn’t enough of the right color of light in the scanned negative for a color timer to bring out.  This is a good example of the fact that, the bottom line is that, simply by nature of their discontinuous spectral distribution, even high CRI LEDs will never accurately reproduce colors on screen regardless what can be done in post. 

 

You have to be wary of all the claims made by LED head manufacturers. Whenever a new lighting technology comes on the market, the manufacturers put a little spin on the scientific data which has a tendency to cloud issues. For this reason, to pick the right LED luminary for a particular job it helps to have a thorough understanding of the technology.  For our company newsletter I have put together an overview of the technology and what LED products are available for motion picture lighting (available at  http://www.screenlig... Output AC LEDs.)

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental and Sales in Boston


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