Peanut_the_cat Loc: Bradenton, Florida

I have always assumed that if the camera is set to "Auto" white balance the color temperature was measured at the, say single focus point. But now I wonder if it is based on an average of what is displayed in the viewfinder?

Or again is is measured from your shooting position. Like if you're in a tungsten light flooded room, 10ft from a open window, and shooting through it with a telephoto lens. Is the camera taking a WB reading from your room position, assuming no part of the room is included in the composition. I doubt that scenario would be true.

PixelStan77 Loc: Vermont/Chicago

Nearly all cameras will have an Auto White Balance setting where the camera will meter the light and do its best to figure out the proper white balance automatically. It is taken from what you are trying to meter. Conventional photographs strive to attain the most correct White Balance where the whites remain neutral, without any tainting of other hues. Some cameras are better at this than others.

burkphoto Loc: High Point, NC

AWB = Awful (automatic) White Balance. The camera averages all the colors it sees, acts *as if* that color were neutral gray, and balances the color response to that average. It's only accurate if everything in the scene averages out to neutral!

If you're photographing a sequence of differently-colored subjects, then each may have a UNIQUELY WRONG color balance!

White balance settings affect JPEG files generated by the camera. While they are stored in raw files, they do not matter, because you can change the white balance any way you like when processing the raw files.

If you use AWB to photograph a red-headed girl in a red dress against a red background, her face will be ashen cyan! If you photograph a blond guy in a yellow sports uniform against a yellow gym wall, his skin will be blue! If you photograph a green car in a green grass field, the person leaning out the window will have magenta skin!

These are extreme examples, of course. But they illustrate the principle. It's the same as the light meter — For perfect results, you must point it at a neutral gray, 18% reflectance test card or target. That's why pros who record JPEGs on site use tools such as the Delta-1 Gray Card, Photovision One Shot Digital Calibration Target, or Expodisc.

There are many similar test tools... Search "white balancing accessories" and you'll find many.

In the film days, we used finicky color temperature meters and Wratten gel filters to balance lighting to color slide film. Now, we just custom white balance against a target... It is generally MUCH more accurate.

BebuLamar

The Nikon D2 series have a sensor on top of the prism to aid for WB. I think it's a good idea but Nikon dropped it from the D3 on.

LoneRangeFinder Loc: Left field

Are you certain this is how AWB works? Nikon says: "...We can simply set auto white balance and the camera will read the scene's color temperature (basically the hue and intensity of a particular light source, measured in degrees Kelvin) and choose a setting from its collection of pre-programmed adjustments."

They suggest the camera is reading the color temperature of the light source(s)….-- not the color of objects in the scene. It seems (to me) that you are confusing AE with AWB.

Perhaps if you posted some examples to clarify?


Before the advent of digital… I used to do film/video lighting and we might gel the window light to balance that light with the indoor lighting. We would also white balance before shooting individual scenes and then fine-tune with the camera generated color bars when in post production.

GoofyNewfie Loc: Kansas City

I've been curious about that myself. Seemed like a good solution if your shooting position had the same light as your subject. Must not have been that much better if they dropped it.
For those with inquiring minds, the white receptor above the logo on the prism housing is where the WB is read.

Brian in Whitby Loc: Whitby, Ontario, Canada

I use daylight colour balance all the timecand correct in in LR if necessary. The only situations requiring accurate colour balance are product photography and portraiture. In some cases using colour balance is counter productive. Fot example if youvare shootingbin the golden hour, you will lose that beatiful warm lighting and a sunset will be corrected out existrnce.
Some colour balance issues cannot be corrected using colour balance settings. In som cicumstsnces different adjustments have to be made to various parts of photo. In camera colour balance is at best an approximate solution.

Jim Bob

Nice info. Great job.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

I've done a web search to answer your question but came up empty. For certain, auto white balance is not determined on a single spot. It is an average, probably more like having a built-in Expodisk, or some means of averaging all the colors in an image, then producing an ad-hoc white balance.

I did a write up several years ago on how to do this white balance method manually in Photoshop:

http://pixeldiarist.blogspot.com/2012/01/correcting-color-cast-in-photoshop.html

TucsonCoyote Loc: Tucson AZ

....I believe every company has that special "Sealed-off" room where they keep all the real great stuff they've pulled off their products ! :)
....I noticed the same thing in the automotive industry (was my line of work) ...whenever they added something that obviously worked and made sense....instantly the next year it was shelved ! :roll:

anotherview Loc: California

A simple tweak in Photoshop can set the Mid-Grey Point, obviating a color card or other accessory.

MtnMan Loc: ID

Unless you have that one camera with a separate sensor or point your camera at the light source to set the white balance your camera is using reflected light.

If you shoot jpeg it can be an issue. In that case you can use a white or grey card or coffee filter to set it manually.

I just shoot RAW and change in Lightroom when needed.