Black text was showing chromatic shift in front of and behind the focus point (at the center of the sensor). (It is not limited to text — you can also see it in the remote control button at the top.) So, of course, I had to do some testing. I designed this text target:
Then shot it under different light sources and angles.
The foreground text is consistently slightly warmer (redder) and the background text slightly cooler (greener).
The Fuji lens also shows this color shift.
As well as the Canon lens on a Canon 7D.
So this effect appears reproducible in multiple cameras and lenses from multiple manufacturers in various lighting situations.
So what is it???
- Doppler Shift?
- Chromatic aberration in the lens? (unlikely?)
- Which usually affects high contrast transitions at the edges of the lens and this is usually one color (purple)
- This is dead in the middle and different between foreground and background
- or something else?
I’ve searched all over Google for information, but no luck. Here are some search terms in hopes that someone is also searching Google:
- Black text looks warmer or cooler, redder and cooler, bluer, greener
- Out of focus text looks warmer or cooler, redder and cooler, bluer, greener
- Foreground text warmer color
- Background text cooler color
If anyone knows, I would love to hear from you.
I know this is probably easily fixed with software*, but I’m trying to do as much in-camera as I can.
*I was a professional graphic designer for years and know Photoshop intimately. I’ve also used a number of photo workflow programs for color correction. I can easily fix this (mostly with just white balance correction), but I will always know that something interesting is underlying the surface, and I want to know why it is there. Call me curious.