White Balance

Copy and paste the link below or click on the post title "White Balance" to go to a short article about White Balance:

http://www.scribd.com/doc/6455684/White-Balance

Color Problems: Part 3

I then take a second exposure, using values that bring the red histogram back within reasonable range. I say reasonable because there may be spikes of red and yellow which are simply NOT capture-able (is that a word?) by your sensor. This looks like a pretty under-exposed image on the LCD, but I take it anyway.

When both images are opened in Camera Raw (or whatever software you use), there is visible detail in the darker one within the areas of red that were blown out on the original exposure. When I blend those two together, I have one image which maintains detail throughout.

Color Problems: Part 2

So here is the original image. Again, the luminance histogram (the black-and-white one) tells me that the exposure is just fine. Experience tells me, however, that red is n easy color to overexpose, and I check the RGB histogram. Imagine my (lack of) surprise when it shows me that the red channel is way blown out!

I take my first exposure based on the luminance histogram, and you can see above the areas of red next to and in front of the Japanese beetle that have no detail whatsoever.

Color Problems: Part 1

Yes, I know it's not a bug, but I will use it anyway to illustrate a point that I stumbled over recently while photographing birds with Matthew Studebaker, who is a superb workshop leader and an encyclopedia of avian knowledge.

The luminance (black-and-white) histogram for this bird read just fine in the field, with no obvious burnt-out highlights. Imagine my surprise when I opened the image in Camera Raw and found that there was a color highlight burnt out to the point where it was not even retrievable! The yellow on this bird's chest and throat contains NO detail. I could not even use my trick of bringing over two images and blending them--even grossly underexposed, sorry, NO detail in the yellow. Ray Klass, Photoshop Guru extraordinaire, showed me an another technique, an old printer's trick called "plate blending", which has to do with bringing detail from one channel back into the original image. The problem is that there has to be detail in one channel to begin with. In this image there was none. A potentially interesting shot, but unusable.

This image awakened me to the purpose of the RGB histogram which Nikon has so kindly included in most of their newer cameras.