Today I received a new batch of prints from a lab. This time I used two new digital post processing steps that I didn't used before: I used Topaz sharpen AI for the final sharpening, and I used some pre-toning bias to compensate for B&W of the color process.
I observed two things, but I am not sure if my conclusions are correct.
First thing is about sharpening. On my display, I could see some white hallows (at some sharp edges). On the print of the same image, I can't see the hallow! It looks like what I saw on display was just some pixel aliasing and it disappeared on the print because the print resolution is much higher than display resolution.
The second thing is about my pre-toning to achieve true black & white prints. When sending gray scale image to the print lab, the prints generally come out with a slight blue cast (bright white paper, color process). So, my idea was to add a slight warm tone to the file (not a gray scale file anymore), and yes, I compared the new prints (with the warm tone bias added) to the previous batch (without bias), I can see the biased batch is closer to true black & white. However, the white areas of image don't match the white of the white borders! So, I came to the conclusion that my lab didn't calibrate their machine to have pure black & white, but they probably calibrated the machine so that the white of the print (color silver process) matches the white of base paper
. Hence the impression of blue cast of prints sent as gray scale images. Is my conclusion correct? If it is correct, it means I have to select the types of paper that are naturally neutral white, so that no toning / bias is needed to achieve true black & white. Is this correct?
Last edited by biz-engineer; 04-21-2021 at 09:00 AM.