Same manual camera settings under continuous light but some pictures are yellow and some are blue

Question

I recently did a product photoshoot.
After a few pictures, I noticed that some of the photos are warm coloured, some of them are cold. I have not touched the object, my camera was on a tripod, and I used the same settings (in manual mode) for every picture. It is really annoying because I need to create a GIF from about 15 photos and some of them are yellow, some are blue. Even some photos turned out half yellow / half blue on the same picture.

Here is an example showing the different colour temperature. They are shot with the same settings, same light, same camera, same tripod, etc...:

For the shoot, I used two softboxes (continuous light) and they remained at the same place for the whole time. These are my settings (identical for all pictures):

• Focal length: 50 mm
• Aperture: f/5.6
• Shutter speed: 1/320
• White abalnce: 5260 K
• Spot metering

I was wondering if the problem was that I had my camera set to spot metering mode, but I am not sure.

Any suggestions or ideas why is this happening?

I shoot in RAW, so I know that I can fix this in Photoshop, but it's a lot of work with 15-20 images. Especially that it says that the yellow and the blue images have the exact same level of temperature and tint. So I probably have to reduce the temperature of the yellow one to match with the blue images but that's very complicated, because not all the images are the same.

Answer 1

Your LED lights are likely using pulse width modulation (do you have dimmers on them?). White LEDs attain their light using a fluorescence effect that creates yellow light via fluorescence from the LED's "native" blue light. When the LED is driven with pulsed current, the blue light will change faster than the yellow light follows, particularly on the on-off transition.

The other possibility is that room lighting, like fluorescent light bulbs, adds pulsed light with a different color balance.

Of course the elephant in the room would be if you have a setup with adjustable colors where separate dimmers using pulse width modulation are on different-colored LEDs.