do LED lights work with colour film emulsions?

[themagickite]

I'm just wondering if LED lighting is suitable for shooting 16mm colour neg or reversal.
I've heard that electronic lights like LEDs have spikes in the red green and blue, this is apparently a problem when shooting on film, but i've also heard the opposite. anybody know for real?

also,
are there any flicker issues? (at a variety of frame rates)

cheers

 

[Cool Lights]

In digital mediums we have white balance and in controlled conditions that takes any green spike that might be present out pretty well except in the worst offending CRI types of lighting. Minus green gel will be commonly used in film when using fluorescents and LEDs to correct them and let them mix well with other lighting. Fluorescents have spikes as well but people use them all the time in film going with the highest CRI and/or with minus green filtering. You can't really generalize though and you just have to do some tests to see how it comes out with the particular fixture you want to use. My hunch is with minus green, there won't be an issue.

As for flickering you can't generalize on that either. Some fixtures might and others won't. I can definitely say our LED fixture doesn't flicker.

Some of the CSI shows use LED fixtures quite extensively from what I've heard and I believe they still use film on all those.

 

[sunporchmedia]

I hope to have more experience with LED in the near future, but here's what I can say about film and the green spike issue generally:

Film emulsions are much more sensitive to the green spike than video, and much more than the eye, due to photochemical nature of film. Not all CRI ratings are created equal. Some fluo bulbs with high CRI keep some of the green spike but add extra magenta phosphors to balance it to the eye. This works well for video but not as well for film. Kino Flo bulbs achieve high CRI by nearly eliminating the green spike, but at the significant cost of overall lumens. Kino brand bulbs are still the gold standard for film, as far as I know, because of their superior taming of the green spike.

If you have ever been on a film location with "practical" fluorescents, there are three general approaches used: 1. replace all the tubes with high CRI, high output tubes such as Kino tubes. 2. Gel all of the tungsten movie lights with plusgreen and blue to match the fluorescents. 3. Gel all the practical fluorescents with minus green and possibly orange.

Film DPs use expensive color meters to read the exact minusgreen and CTO values needed to precisely correct fluorescent lights found on location. This is because even a trained eye can't see the green spike the way film renders it. In fact, once corrected for FILM, a practical fluorescent often looks very magenta to the eye.

Some modern film emulsions have been formulated to be less sensitive to the green spike than in the past. Digital intermediate processes have increased the control in color correction compared to the old photochemical color timing processes. So these factors have lessened the problem somewhat.

As compact fluorescents become more prevalent in homes and the workplace, it gets even more complicated, since there is no standardization from brand to brand or even batch to batch, as to color temperature (warm, cool white, daylight) or color accuracy (what is the CRI and how was it achieved). It's nearly impossible to find a CRI rating on a consumer compact fluorescent bulb. As Richard pointed out, video is very forgiving for all but the worst offenders (or if you are mixing a lot of different light sources), but film is a different animal.

Finally, there is the matter of the "look" you are trying to create. If you're going with a very stylized look, color balance and color accuracy may not be very important, as long as you control it for the look you want.