Hi there!

Raw will record values such as white balance and color space, but does not lock them in. They can then be altered in the Raw converter with no loss of information.

The "no loss of information" part is where the Raw converter differs from doing the same thing in Photoshop itself. Commands such as Levels and Curves change the image drastically, and some information is discarded.

White Balance is important to get right. Light is measured in degrees Kelvin, and the "warmer" light (such as indoor incandescent lighting) gives off a yellow glow, while "cool" light (outdoors on a cloudy day) emits a bluish tone. Get the balance wrong, and you give every color in your image an unwanted color cast.

So, how do you know what the color temperature was at the instant you took the picture? The old-school answer to that is a grey card. A grey card is just what it sounds like, a piece of cardboard with a know shade of grey (say 50%, for example). The first image you take under a given lighting condition is to fill the camera frame with that grey image. The do the rest of your shoot normally. If the lighting changes, shoot the grey card again. When you start processing your images, you open the grey card, and tell The Raw converter to alter the white balance so that that image shows up as 50% grey. Then you apply that exact same adjustment to all images shot under the same lighting conditions. Bingo! spot-on white balance conversion.

That's the theory anyway. It sometimes doesn't work that way though. If you use a flash, you can create a brighter spot on the grey card, due to reflection. Now, which area is truly 50% grey??? Besides, it's always better to get things right in the camera, if possible, right?

To learn how to do that, Google the term ExpoDisc. It's not going to be inexpensive, but how important is getting the color of your images exactly right in camera?

Food for thought,

- Joe U.