Blown out colors under LED party lights

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drummondb

Well-known member
I assume we've all seen this? Shooting in a party environment with strongly-colored LED party lights (reg, green, blue, etc.). The waveform and zebras all look fine. No clipping, but when you look at the footage at home, faces look clipped. Luminance on the waveform seems fine, but when you switch to an RGB waveform, certain colors are skyrocketing over 110 IRE, and are often blown out. Pulling the individual color back down below 100 does not help. If it's clipped, it's clipped.

I've been shooting a lot of weddings with C100's lately, and I'm constantly running into this. I'm not sure there's any solution using my current gear, nor even what types of scopes I'd need to use while shooting. Seems like to avoid color clipping, I' need to massively underexpose the luminance of the image. And nothing in post seems to help.

Are there any cameras or types of sensors that handle this situation better? What about esoteric options, like the F35's CCD sensor? And I'm curious, how does motion picture film handle this situation?
 
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Yeah, tricky scenario for sure. Sometimes it may not even be flipping, but when you have a fully saturated blue light, the sensor is starved of red and green, thus lacking the fidelity to fully render a good image. But yes, clipping does account for a lot of what happens.

A a monitor with RGB parade scope would be helpful. But only to a certain extent. If the lights weren't changing and were only one color, you could go into your camera settings and account for that color Chanel on its own. However, that is neither ideal or even the case ever.

If you can add fill light to bring up the ambient levels and also minimizing the saturation effect of the disco lights, that can help you to manage it better. Cameras with larger dynamic range and cleaner noise floor will also be able to handle this better.
 
Yeah even red and Arri have issues with primary colored highlights to some degree. Problem is when one channel is clipping the color science is basically guessing at how to render color since it's missing data from that channel besides that it is somewhere beyond clip. Seems to me the best way to handle this is use a camera with as much DR as possible and underexposed to preserve all channels as much as possible. Some cameras even have gamma modes that are pretty goood for this but horrible for anything else. For example Sony has rec709 800% which clips way 1-2stops early compared to all other log and cine gammas but in doing so does less guessing about how to render clipped colors... Problem is in extreme situations there may not be a lot to do especially since heavily unxerexposing is not always an option especially in cameras with limited DR. Its a lot easier to avoid color issues on skin than it is on brighter values like colored light sources in the scene.
 
drummondb said:
I assume we've all seen this? Shooting in a party environment with strongly-colored LED party lights (reg, green, blue, etc.). The waveform and zebras all look fine. No clipping, but when you look at the footage at home, faces look clipped. Luminance on the waveform seems fine, but when you switch to an RGB waveform, certain colors are skyrocketing over 110 IRE, and are often blown out.
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Yup. Waveform and zebras are about luminance levels, not chrominance. The old assumptions (for example, that only "sane" lighting would be used) mean that our old tools (waveform monitors, zebras, etc.) don't work well in the new world of single wave length light sources.

This is a problem of using cameras designed for full spectrum lighting, under very discontinuous "sparse spectrum" lighting like colored LEDs. Drives the camera sensors and firmware crazy.

I'm thinking (for better or worse) that one of the things we should all probably be doing is setting expectations for our clients. Tell them that single color LED lighting drives cameras crazy, that we'll do what we can to control it, but it is what it is.
 
I thought this thread would be about the Sony crazy color highlights (a7S and the like). Custom White balance solved that one: set it to 5000K or lower and... well, it still looks awful because those lights are atrocious, but at least it's not clipping hell.
Original thread about this here.
No idea if this will work on other cameras.
 
Wow, I didn't know about those Sony mirrorless woes. So looks like the Canon cinema EOS line are not the worst with this issue? Anyone ever use an F35 under those lights? People seem to idolize that CCD sensor.
 
Samuel H said:
I thought this thread would be about the Sony crazy color highlights (a7S and the like).
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I did too.

Has anyone tested shooting Log, & applying an ALEXA-like LUT (e.g. LC709A) in post?

Art Adams wrote, "...Alexa limits color saturation in highlights and mid-tones, something that most video cameras either don’t do or don’t do as well. As the video clip in that article shows, Alexa color saturation locks once the luma value of any hue approaches middle gray. (Middle, or 18% gray, falls at 40% on a luma waveform.) As exposure increases beyond middle gray a hue will brighten but its saturation will remain the same".

Sony's LC709A LUT was designed for SLog but should be able to be ported over to other flavors of Log using LUTCalc.

Below is some background material by Art Adams.

What Alexa and Watercolors Have in Common

http://www.dvinfo.net/article/production/camgear/what-alexa-and-watercolors-have-in-common.html

Hacking Alexa's Rec 709 LUT into a Sony FS7/F5/F55

http://www.provideocoalition.com/hack-alexa-lut-into-sony-f-cameras

LUTCalc: Trials, errors, and a full-range LC709A LUT

http://www.provideocoalition.com/lutcalc-trials-and-errors-plus-a-free-lut
 
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^ Those Art Adams articles made me change a bit how I finish my color grading: after everything is done, I apply a Colorista III filter reducing saturation A LOT, with a luma key that ramps from 100% at the brightest colors to 0% at around 40-50% brightness. Highlights look a lot better with this. But it doesn't fix stuff that's absolutely horrible to begin with, i.e. these colored LED thing.

Edit: I used that final touch it on this video, and I think the highlights look awesome, particularly in the glass house (the statues, not so much, but they were way worse before the filter) (beware of will-drill-your-brain Korean music):

 
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This is the cinematography section. So Im gonna chip in with that hat on.

-These LED are only lights - just very bright in a single channel.

Order different fixtures or Gel them, ND them, or light up to them (bright fill).. no problem.


-The second thing is 'do they do something genuinely weird?

What could this be?

The only think I can think is that they chuck out a lot of UV just off the eye visible spectrum that cameras 'read' as blue.

I certainly think testing with IR UV cut (even stacked up) could be worth consideration.

And yes post.. the highlight rolling can help.

S
 
Samuel H said:
But it doesn't fix stuff that's absolutely horrible to begin with, i.e. these colored LED thing
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Surely there isn't much that could be done to footage that has Uber-clipping already burnt-in, but what about shooting Log instead of Custom, & taming the saturation in post, perhaps with the LC709A LUT? From what I've seen on the F55/5, & FS7, this eliminates the issue.

I know shooting Log on a 8-bit camera is not ideal but it's got to look better than Uber-clipped footage.
 
I shoot log. These damn things are just way too bright and way too saturated. The only thing that really helped was the WB trick on the Sonys, and it's still ugly as hell, just not plain horrible. You can just hope for "not completely awful". I hate these LED fixtures.
 
I've started by asking everytime I shoot something (mostly live performances in my case): "is there LED lights?". If it is, I simply tell them it most likely will look like crap.
They are the bane of my existence... all these cheap skate / clueless venue owners. Even if I'm not filming I think they look like crap. Horrible.
 
Samuel H said:
I shoot log. These damn things are just way too bright and way too saturated. The only thing that really helped was the WB trick on the Sonys, and it's still ugly as hell, just not plain horrible. You can just hope for "not completely awful". I hate these LED fixtures.
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Thanks!
 
morgan_moore said:
Order different fixtures or Gel them, ND them, or light up to them (bright fill).. no problem.
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I doubt gelling will do much good. Your typical LED "party light" gives you a single spike of a single color. By design. They want blue to be blue, not mostly blue. If you then gel your blue LED with, say, some level of CTO gel, it simply acts as an ND filter.

Gels are basically low pass filters. A CTO gel lets lower frequency (longer wave lengths) like red, orange, and yellow pass, but attenuates higher frequencies like green and blue. But if an LED doesn't provide any red, orange, or yellow light there's nothing for the gel to pass. All the CTO gel does then is attenuate the blue. To the camera this looks like an ND filter because it's attenuating all the available frequencies -- in this case, the only available frequencies are blue.

The end result is not what you'd expect -- there is not a lowering of color temperature toward orange. The color temperature remains constant. Only the level of light has been lowered.
 
But if your blue light is giving f22 on a light meter and the rest of the scene is f4 Nd on that fixture is surely exactly what you want?
 
I always dial the chroma levels right down for these shooting environments - helps a bit, and then pull down the highlight saturation in FCPX
 
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