CHROMiX

is there a neutral white balance

Hi,

I am trying to figure out if there is a certain color of light I can use to set the white balance on my digital camera so that it will preserve the color casts caused by the current lighting.

The other day I walked into a grove of trees and the lighting was very nice and I wanted to take a picture of that scene. However if I take a white balance, that would remove the attractive color of the light, I wanted to preserve that color. I want the scene I see in the camera display to match what I see with my eyes.

I’d like to bring my pda/pocket pc with me and display a .jpg of a “neutral” color on it to take a white balance from so the camera will preserve the color of the lighting when I take a picture.

As a first step: are there any rgb values such that if I display that color on my calibrated computer monitor and then take a white balance with my digital camera, the camera will take pictures that preserve what ever color casts may be present when a picture is taken?

If I display a test pattern on my computer screen and take a white balance off the white portion of the screen the colors r,g,b,c,m,y look the same to my eyes when I look directly at the computer monitor or look at the camera display with the camera pointing at the computer monitor.

However if I then point the camera around the room, everything looks too yellow. So I add a bit of yellow to the white swatch on the computer screen and take a white balance so that the camera will remove a little yellow from it’s pictures. Then I point the camera around the room and things look similar when I look directly or look through the camera.

However if I point the camera back at the computer monitor it looks too blue - which is exactly what you’d expect, actually, if you take a white balance from a yellowish light.

Can anyone suggest a “neutral” color rgb values or explain why this won’t work?

Are any of the camera presets, ie sunny, cloudy, flash, incandescent, flourescent likely to do this?

Thanks!

There are some fine responses to this question at:
http://www.dcresource.com/forums/showthread.php?p=402674

However, it seems that no one is answering your actual question of what RGB numbers to use.

It is important to remember that RGB numbers are not colors. They are just numbers. And these numbers will give you different colors on different devices. It’s rather like numbers on a toaster. What you’d really want if you’re looking for numbers at all would be “Lab” values. These actually represent color. If you want white, the Lab value would be 100, 0, 0.

These articles from our newsletter can aid in the understanding of this:
http://www.colorwiki.com/wiki/Color_Management_Myths_11-15#Myth_.2311:_Printing_a_profiling_target_is_a_good_way_to_evaluate_a_profile

http://www.colorwiki.com/wiki/The_Color_of_Toast

Keep in mind that when you are looking at your sunset through the trees, you are not actually seeing it as it “really is” either - your eyes are auto white balancing to the scene also.

So, if you want a practical answer to your question, I would recommend:
White balance to the scene as normal, then adjust in Photoshop to get the warm color back into the scene that resembles what you remember.
If you want a technical, non-practical answer:
Bring a laptop into the woods that has Photoshop installed, and is calibrated and profiled to a D50 white point using a measurement device like a colorimeter. Then open a Photoshop blank white document into a working space with a 5000 K white point like ProphotoRGB or ColorMatchRGB (NOT adobeRGB or sRGB) - and white balance to that. Then you might have some assurance that the white on your screen is producing something close to normal white daylight. But I wouldn’t guarantee it!
Fascinating question. Thanks for posting.

I don’t think using a display to white balance your camera would be a good idea.

You are on the right track though. Although the white balance setting you would need to achieve the effect you are looking for would not be the same every time (even if you could get a screen to display an accurate white).

I would recommend thinking about what the dominant light type is. In your tree grove example the dominant light was most likely shade with streams of warmer light. If you want to capture the feel of the warm light set the camera on shade (in this example). If it where a sunset you could try daylight. better yet try setting the camera to a specific kelvin setting (if you have that option) that way you could make small changes to achieve the effect you are looking for.

This is an example of one of the major differences between a camera and the human eye. Even with a good white balance setting the difference between the two types of light will be more pronounced than what you will see because of the way our brains compensate for these differences.

Saving a RAW file and making these corrections on a calibrated display would be the best option because even if you were able to get the effect you were looking for on the cameras display you would still need to correct the file some later to achieve the same look in print or on your computer screen (the cameras display is not calibrated).

Hope this helps,

Very helpful thread, thanks everyone. Found exactly what I needed here to sort the white balance on my SLR out.