White balance setting to match the way we perceive things

Question

A white piece of paper on my table does not look as white in the evening when the light bulb is illuminating it compared to daytime when the Sun is illuminating it. The difference is much smaller than what you would get if you assume that the brain does not perform any white balance correction at all. However, it seems to me that the brain does not perfectly compensate for the change in lighting. If I set the white balance "correctly" in my camera to make the white piece of paper white, then the picture I get is not precisely the way things really look in the room.

The question is then if there is a practical fine tuning procedure to get the picture to match what we actually observe, similar to how you would go about getting a correctly exposed picture (in that case the camera measures the amount of light to determine the exposure but that would make bright objects to become a bit too dark or very dark objects would become too bright, so we have to use exposure compensation to get it right).

Answer 1

I've been experimenting with what seems to me like a practical method of fine-tuning, which is basically just "morphing" between two white balance settings, each of which is a "correct" setting for one of the lighting situations in a mixed light image. This seems like a nice way to nudge a single slider around, rather than juggling temperature and tint. For instance, for an outdoor photo with golden hour sunlight mixed with shade, you would use known-to-be-correct settings for each, and mix between them. For a situation like streetlights (where the color is likely to be just about anything except a black body radiator these days) you might blend between a full correction for the light and a familiar baseline such as daylight balance to get something that resembles your actual perception of the scene (or at least how you want to remember it).

I'm not aware of any RAW software that implements something like this yet, but you can play with it by fading between fully "corrected" layers in appropriate image software. Meanwhile, I'm creating interpolated presets in the software I use for addressing the most common cases. Sorry if this is incoherent or less-than-relevant, I'm slightly delerious with a cold at the moment... but that's when mad science is the funnest. ;)

Answer 2

Just because the paper is white does not necessarily mean that it appears to be white in the image. Your camera can only see the light that is reflected towards it.

It's essentially the same "problem" that you have with measuring the amount of light to find the correct exposure.

• You never know if what you see is a bright object that is in low light, or a dark object in a lot of light.
• You never know if what you see is a green object that is in white light, or a white object in green light.

The available solutions to this problem caused by receiving only the reflected light from the subject are:

• eyball it In the digital age, this is what a lot of people use for either one. Take a few test shots until the exposure looks correct. Take a few more until the colors stop looking funky and the white balance is ok. If shooting raw, you have a lot freedom to adjust the exposure in post and even more so to adjust the white balance.
• meter it There are exposure meters that allow you to measure the amount of light before it bounces off the subject. This is useful in studio, to dial in ratios between different light sources. Yes, there are also color meters that allow you to measure the white balance/color of light. They are expensive (>1k$) and not as common as exposure meters. They are useful to keep color white balance consistent across many images or in video productions. You don't want everything to look like bathed in the light of the sunset just because that bulb in your flash or video light slowly decayed over the course of the production and changed its color.

There is no such thing as a correct white balance just like there's no correct exposure either. You have to adjust both to recreated the vision that you perceived when you took the photograph. How exactly you are with that is your creative freedom.