Digital BW, The Print

> The compression probably messes up some of the transitions 
> but I think the main thing you are seeing with the vertical 
> lines is just the individual 256 steps of gray.  Photoshop 
> will create two kinds of gradients -- 256 hard edged steps 
> and smooth dithered gradients.  The "dither" option in the 
> Gradient tool there a check box for the two kinds.

I think there are more problems than just the individual steps
showing... Here I've increased the contrast on the stepwedge to make the
problem more visible, then enlarged it quite a bit:
http://daniel.staver.no/img/compressedstepwedge.jpg
 
> It's real easy to fix up the 21step.  Just select the top 
> half and make a new gradient with dither on.  Select the 
> bottom half, make a gradient with the dither off, and 
> posterize to 21 levels.

I made a new cleaned-up version without artifacts and updated the
technical.psd file with the new stepwedge. I also made a smaller version
of for test prints. All three files are available here:

http://download.petraflux.com/technical.zip (3.59mb)

--
Daniel Staver
http://daniel.staver.no