Inconsistant color balance with inexpensive LED lights?

[pixelpete]

Has anyone had difficulty with consistent color balance with inexpensive LED light sources?

For a good many years, I shot class composite images for a faculty friend who was the director of program at a university. I placed the images in InDesign, and output a jpg composite image for printing. The composite was eventually mounted on the wall to show the past students who had graduated.

I retired, and their program purchased a set of lights and did their own photography. I agreed to do the InDesign work. While assembling the images, I found the color balance was all over the place. I assumed that it was because they did the shots themselves. The next year, I shot the composites for them using their set up. I set up the white balance with a gray card and made sure no one touched the lights between settings. The shoot consisted of students arriving on two different days and capturing a minimum of 24 students per session.

I had the same problem. The color balance was all over the place. The only thing that I could think of was the color temp of the lights varied. Control of the lights consisted of a slider to adjust the color temp.

Has anyone experienced anything like this?

[Manfred M]

Short answer - yes.

Cheap LED lights don't have a smooth spectral response and you will get spikes in certain colours, which gives you the colour responses that your see. Cheaper LED lights reduce the driver current to dim the lights and that results in some strange colours and I suspect that is what you are seeing. The other way of dimming LEDs is to turn them off and on quickly, so for instance, if you run the LED at a 50% setting, the LED is on half the time and off the other half. I believe this technique tends to be used in more expensive dimmable LEDS.

Rule of thumb, for good colour rendition is to use lights with a CRI (colour rendering index) of 95 or higher. I've seen this with non-dimmable LEDs, but can't recall seeing CRI stated on dimmable ones. If the package does not state a CRI value, you can assume that the colour performance won't be particularly good.

[DanK]

Yes, it’s a matter of the entire spectrum, not just white balance. A high CRI is essential but not enough because that scale, created during the days of fluorescents, excludes some of the reds. The best bulbs will give you a measurement for R9 also. That too should be over 90, ideally over 95.

For years, I’ve purchased Soraa bulbs, which are high on both indices and dimmable. However, their BR 30 bulbs have become ridiculously expensive. I used to pay something like US $ 22 each, but they were in short supply when I last needed one, and I had to pay almost twice that. Hopefully they will go back down.


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