Adjusting W/B for RAW

I see talk about adjusting white balance when converting RAW files, but I am not sure where to pick to provide a good WB. What if there is no real white in the photo to choose from. Am I missing the concept somehow? What is the best way to know if you NEED to adjust WB?
Steve

Sometimes there is NO WHITE POINT at all (or black point - shadow). In such case you can't use Custom WB while converting from RAW to TIFF. But there are some options:

1. Use Custom WB while shooting (it's not a problem to find a piece of white paper)

2. Use one of the preset WB setting and try to choose the best one while converting

3. Convert as is and use PhotoShop + Curve (Level).

And also,

In ZoomBrowser

Step 1. select a picture with a simple WB point
Step 2. select the picture without a possible WB point
Step 3. select a custom conversion from RAW
Step 4. a dialog opens for the 1st picture you selected
Step 5. set the WB with picker, adjust settings, click OK
and the second picture will get the picked WB and settings from the first image. Voilá! (NOT "Viola!" like most people seem to shout, viola is an orchestra instrument )

I didn't even know that ZB can keep settings for WB from previous picture (Or I got you wrong). Thank you, Pekka.

Pekka wrote:
And also,

In ZoomBrowser

Step 1. select a picture with a simple WB point
Step 2. select the picture without a possible WB point
Step 3. select a custom conversion from RAW
Step 4. a dialog opens for the 1st picture you selected
Step 5. set the WB with picker, adjust settings, click OK
and the second picture will get the picked WB and settings from the first image. Voilá! (NOT "Viola!" like most people seem to shout, viola is an orchestra instrument )

The custom WB picker does not require a white point: it just requires a neutral shade of grey, anywhere between 0% (white) to 100% (black), and it corrects the image accordingly by shifting the color curves.

My workflow is simple: I have a cheap Kodak Grey card (18%) that I used to use to set-up exposure in the old non-digital world. I've changed its use in the following: if you have the time, take a shot of this grey card as your first image in the series with the same lighting.

With the Twain Driver (or Zoom Browser), this grey image will appear first.. Select it with the other images you want to convert, and apply the custom WB to it.

I have cheap tungstene lights that are not white calibrated, and a couple of building projectors. I use this technique to have a quick color correction after the fact... no need to use gels to correct the light, at least as long as you don't mix different light colors.

nadim