All scans were Raw which gave me uncompressed. I ran VueScan at 4 passes for both 24 and 48 bit scans. I ran the 48 bit test with answering both Yes and No to the 48 bit linear question. I ran comparisons on two printer targets I had made a while ago - Costco Kirkland Glossy and Staples Matte. My PP setup is an Epson V500 scanner and VueScan Pro - profiles for a Canon ip4500. I tried your suggestion of the 24 bit scan instead of 48 bits. Mike: do you recommend scanning for printer profiles using 24bit or 48 bit mode? Incidently the colour space generated from the 48bit image is generally slightly larger than the 24 bit Hence 'No' in my case is the correct answer as you suggest. This histogram looked good and the prints very close to how they should be. In response to your suggestion I regenerated the profile choosing 'No'. And subsequent prints were much lighter than they should be. The resultant PP histogram was quite semi-circular ('bubble') rather than a linear shape decreasing towards the right. Of course, PP presented the 48bit linear question and I answered 'Yes'. I decided to scan the printer profile images in 48bit mode rather than my usual 24bit mode on my Epson 4990 scanner using 'Epson Scan' (no raw mode). In a normal scan processing modem you would answer NO (it is not a RAW scan) and Profile Prism knows what to do with your gamma curve, If you can set the software (and many of the scanner software twain drivers do not have it) to process teh scan in RAW mode, and save that as a TIF or JPG then you would answer YES. That question that Profile Prism asks is relevent to how the software you used processed the scan. For what I understand from the instructions for a printer profile I need to always select 'yes' to the message 'Is this a 48 bit a linear (gamma 1.0) image and it is being used to profile a printer?'. If I select 'no' to the message I have perfect results.

Epson perfection v500 scanners