Lost of contrast
Hi all, An ideal process and paper would scan the paper value as 255 and its darkest value as 0. Unfortunatly, this ideal process doesn't exist. In order to deal with this, the linearisation procedure was introduce, basically it is suggested by most people here to expand the process print range to those above value (0, 255) and using the curve tool, you manage to obtain a one to one match for intermediate values. This must satisfy most of you, otherwise the contrast problem would have been raised a long time ago. This procedure is called linearisation by most of you here, in the color management world it is called gamut or tone mapping especially in the case of monochrome images. The problem I raise is though this linearisation procedure is easy to do in practice and may pretty well give you acceptable results or prints it as the adverse effect of reducing the overall contrast of your work. In order to find a one to one match between the original and the print you have chosen to expand the range of the print and this as the effect of increasing the print contrast right? Suppose now that you would have chosen to compress the original range to print range, this of course would have reduce the contrast of the original and it would still have allow you to obtain a one to one match again. That's one of the fun things of working with numbers, one can approach a problem different ways and obtain equivalent result. Now lets look at the real thing and compare the original values ranging from 0 to 255 to the actual printed values. The maximum white of the original as been translated to some value lower then 255 and the darkest original value (0) as been translated to some value above 0. It would seem to me, this is equivalent to a compression of the original range to the print range. As explained above, we know that compressing the range of an image (in a linear fashion) causes a reduction in contrast. As I said from the start, you can be satisfied with this effective lost of contrast and keep doing this linearisation procedure as you've doing for eons. Knowing this though, I for one would certainly try to find a better way and I actually found 1 and created another that is just as easy to implement in practice as this linearisation scheme you all seem to use but without loosing as much contrast. Have a nice day to you all, Yves
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