QTR-Quadtone RIP

>... The test strip looks good; I can certainly see the different 
> shades at 4, 3, and 2. 

>So it has to be the scanner (Epson Perfection 3590.) I¹ll 
> see if there anything that can be done with the controls. 

Using just the gray card to adjust the gamma of a scan was a simplification
of using a Kodak Q13 card to do a more serious scanner calibration.  See
pages 3-4 of http://www.paulroark.com/BW-Info/Making_B-W_ICCs-1.pdf   I
found that most scanners can produce reasonably linear grayscale scans if
the gamma is corrected, but if yours can't it becomes much more work.  Your
scanner may have also come with some system to calibrate it. 

Paul
www.PaulRoark.com