White Balance

David Hunt

A recent comment I made on one of Craig Wilson's KAP photos posted at flicker got me to thinking about how my camera handles White Balance. I have always used the Auto White Balance setting on my Canon SD 20, but I thought it would be interesting to see how each of the camera's seven White Balance settings handled an identical shooting situation.

The HAP (Human Aerial Photography) image below was taken outdoors on an overcast day. Sunny and partly cloudy conditions might yield different results for some of the settings. The RGB values where measured in the snow areas of each strip. Ideally all values should be the same, in real life there is always slight variations. The values listed are just representitive of the average.

This is probably a worthwhile exercise for those using digital cameras. It would help you make more educated decisions about camera setup before each flight. You would want to perform the test for the three main outdoor lighting situations; Sunny, Partial Clouds, and Overcast.



SUMMARY
AUTO - slightly elevated blues
SUNNY - Cyan color cast
CLOUDY - normal
Tungsten - Strong Blueish-Cyan cast
Fluorecent - Cyan color cast
Fluorecent H - normal
Manual - normal

Fluorecent H is for daylight fluorecent bulbs
Manual is set using a white object under the same light conditions.

www.kaper.us

Craig Wilson

Thanks for this interesting tuitorial David. So if I take a shot made for instance with cloudy white balance and adjust the RGB levels to the SUnny white balance values, will the image adjust to look like the colors in your example?

David Hunt

Actually this is not a tutorial, it is an exercise to help me understand how my particular camera (Canon SD20) handles White Balance. To completely understand my camera I would want to perform this same test in Sunny and Parial Cloudy conditions because the light temperature will be different for each situation.

In most situations you want your camera to record the colors as accurately as possible. One way of checking how accurately your camera rendered the colors is to read the RGB values in a known white or grey area in the image. The area of the image will appear pure white or grey if the RGB values are equal to each other. This measurement is done with your photo software after you take the picture.

So what I learned form the image above is ,with an overcast sky, my Canon SD20 renders the most accurate colors using either the Cloudy setting, the Fluoresent H setting, or the Manual setting. The Auto setting was close and even with its slightly elevated blue value the image looked ok.

The auto setting is easy to use because you set it and forget about it. Any minor color problems that arise using Auto WB can be corrected in Photoshop. If you want to always exercise total control then use the Manual setting with a grey card or a known white object. As a videographer I carry a white card.

Once you have your White Balance set correctly, all your nice pretty pictures can be modified any way you wish using your digital darkroom. If you like a warmer or cooler look then use the Levels or Curves tools.

Carl

When we received our first DSLR, we went through a slew of tests and white balance was an important one.
One day I showed test images done on Auto White Balance to my boss.
He said; That's a nice looking denim shirt you've got there.
I said; no, it's the green one I'm wearing now.

So now we knew the camera will look at a scene, if it can't find a part of the image which doesn't have neutral colours (Black, white or grey, but not specular reflections), it will make something neutral.

I give photo workshops to professional museum curators and conservators.
For the white balance test , we shoot 2 colour cards. One MacBeth colour checker, because it has neutral sample squares. Images will be neutral.
The other card I made up using sample paint chip from the hardware store.
Using everything except whites, blacks or greys, removed all white borders and glued them in 6 x 5 matrix (30 samples).
Want to guess what the camera did?
That's right, one of those square became neutral.

Most scene do have something neutral, or close to. As the scene changes, so will the white balance. If you're processing images in Photoshop, correcting one is not bad, but forget about doing batch processing, because they're all have a slight variance.
Stick with using one the fixed white balance setting.
If you're shooting RAW, then it doesn't matter what the setting is because it's only an instruction to the complete data set. The instruction can be changed in the RAW software to the appropriate one without losing image quality .

No two camera operates the same.
If your camera only works on auto white balance, DON'T go buy another camera.
Just go have fun and enjoy yourself.