> What I spoke of was for digital cameras and does hold true. > > You CAN recover between a half and one full stop of overexposure. This > is (I think) because the jpg/tiff or possibly the 8 bit lattitude is > narrower than the RAW image can capture. So you can choose which part > of the full available range is used to create the jpg/tiff from the RAW > file and adjust exposure a little if necessary. I do it regularly and > so do many other users.
Usually around 2/3 of a stop, from what I can see by poking aroung in a RAW file. But see below. > White point definition is very different from white BALANCE setting. > White balance is a colour temp thing ONLY. White/black points are > something you can do in software - I always have to do this when > scanning slides for example, and IS an exposure/contrast thing - but > this is not white balance as a digital camera user can control. You can, of course, make white balance adjustments in software, too. In fact that's how the digital camera does it, as well; by scaling the R/G/B readings from the sensor whle converting to TIFF or JPEG. (for example: the 'B' values are scaled by around twice as much if the white balance is set for tungsten lighting as they would be for daylight white balance). The camera (or the software conversion code) doesn't map the full range of the sensor to the full range of the 8-bit TIFF or JPEG, either; if all the camera settings are at normal there's a bit of slack left to allow for increases in contrast, brightness. etc. This margin (together with any extra slack introduced by the white balance scaling) means you can recover some amount of overexposure, although there might sometimes be a very slight colour shift in the most extreme blown-out highlights.
