How to change scan exposure.

[Semi79]

I'd like to scan a water color painting. I recently got help from this community when I asked how to scan to tif to a macbook. It seemed the only available app was/is HP Easy Scan. It's possible to scan in 1200 dpi to a tif file, which is what I want.

However, I've noticed that the exposure is a bit too high. Some of the light blue areas turns out grey or white in the scan, it doesn't get all the nuances of my artwork.  With my old scanner, I used to scan directly from Photoshop and was able to choose scan settings before the actual scan. I can't find anything similar in HP Easy Scan (and I can't seem to scan from Photoshop anymore).

I hope there is a solution as I bought this scanner/printer to work on my art paint -< scan -> print -> scan again et c. It just doesn't work if it's not accurate.

[Semi79]

Edit: Now I learned how to scan from the Apple menu, where I'm able to change exposure and saturation. Alas, it seems that the printer just cant detect those fine nuances of blue in my painting. Changing the settings does nothing. The only thing that's different is that the scanned tiff image doesn't even open in Photoshop. I get an error message saying that there is a missing jpeg marker.

But the real problem is that the scanner apparently doesnt see the difference between light grey and light greyish blue, or light blue/white.