Something I've really struggled with since starting to sell my yarns online has been photographing them and having the color in the pictures match (or really get anywhere close to) the yarn color. I got a good camera; I made a light box; I got some halogen lights from IKEA and set them up on the sides of the light box; and still the pictures required a lot of futzing in Photoshop to adjust the balance. Even though I saved the adjustments into a reference file so I could just drag and drop them onto new photos, it didn't always work; and besides, that's cumbersome.
I'd read something about White Balance a while back and decided tonight to see if I could investigate a little further, see if this problem could be addressed if not resolved. I read an article (here) about WB and found in the Canon 5D manual how to adjust it for my camera.
There are 9 settings, and the last 2 are adjustable further (this is color temperature. I don't understand the units but I can grok the ranges).
So I did a series of 18 pictures - without flash and with flash, on each of the settings, the last two at whatever their default temps are, I didn't pay attention. The ones without flash were too dark and orangey. With flash on, the tungsten and fluorescent settings were VERY blue, the shade and flash settings were on the orange side. The best in my opinion was the custom, at the default temp. Here's a set of thumbnails of the tests:
I think the last 2 on the left, custom balance and custom color, are the best, both in terms of not too blue and not too orange, and in terms of how true to the yarn colors they are.