Highway 61
Revisited
True - this is called not blanking the lowlights out and not clipping the highlights.No, but you need a device to measure the value, like a lightmeter. If you do not measure and adapt it, it can become 0 or 255 and that is what you do not want. You want your darkest part 1 and your lightest part 254 or lower.
Erik.
This can be achieved without any special device, you just need a calibrated screen and a 16 bits per channel full-res. TIFF or DNG file. And, of course, you have to carefully look at your histogram. In case of any doubts, PhotoShop can tell you at what level the darkest parts of the image are, thanks to the pipette. The same for the clearest highlights.
But - this must not be done by advance on the file the scanner will create and save. Otherwise you will post-process a source file having been modified already - not good.
Markus Hartel on his own website and Bob Michaels here have confirmed this.