Digital BW, The Print

.  I can 
> cope with correcting converting verticals but I have not found a 
> method to correct pincushion distortion in Photoshop.  

Try http://www.andromeda.com/
They have a photoshop filter called Lens Doc.
You can purchase it via download. It corrects pincusioning as well as
barrell distortion. I use it all the time. Works very well. It also
has perspective tools that let you square up 
the image as an option to the photoshop perspectine/distortion edits.
The Lens Doc fixes everything perfectly. Once set up. you place 2
pairs  dots on  curved lines you want 
the software to "bend" straight.  You don't have to pace the dots on
lines if there aren't any. They can be placed anywhere on the image.
These dots are just a reference for the 
software to grab something to straighten. You can see the effect all
the way into the center of the image. I was noticing a lot of curved
lines on the edges of my frames, especially 
if there was a bank of windows or french doors on the edge of the
frame. I thought my lens was pincushioning. I use an Arca Swiss 6x9
and I also configure it to shoot 4x5 with a 
conversion back.The problem was confined to the 6x9 roll film only,
and after searching the photo net posts, I believe that my lenses are
fine, the curving was caused by the film 
not laying perfectly flat. I guess roll film can develope a permanent
reverse curl near the roller if more than a few minutes pass between
advancing the roll. This results in the film 
not sitting prefectly flat at the edges, it gets a slight wave,
hence, my getting curved verticles at the edges towards the corners.  

John Luke