Another use of CWB is to enhance Black & White photography in digital camera. Once again, in a nut shell (me going nuts, ha ha ha) :
Traditionally, we use green, blue, yellow, orange, red to increase the contrast in B&W photo, depending on the color of the subject and its surrounding.
Now, IMO, adding any filter infront of the lens will degrade the image quality, though human eye may not be able to tell. But if a low grade filter is used, the expert can tell, only if you compare both shots (with & without) side by side (of cause the contrast will also be different).
Adding color filters also reduce the light reaching the film / sensor. Modern camera wil auto everything will take care of this with you noticing. For cameras of yester-years, one has to compensat this diff. manually.
Digital camera has the power to over come the a/m. You guess it, CWB!!!! So grandfather story continue :
Place the filter infront if the lens (dont need to screw on). Set CWB. Remove the filter. Shoot. Will see color cast, but never mind. Load to PS, use grey scale. Done.
Actually those camera that has color temp adjust. function can just offset the color temp, shot, load to PS, use grey scale. Done.
Do you think 20D (with B&W function) actually has collor filters inside the camera??? Ha ha ha.
I stress again, a/m is my opinion. You can disagree. No problem. :thumbsup: