Interesting. Let's see if we can solve this. Do you see this shading on both vertical and horizontal compositions, and is the shading always on the left and right in both vertical and horizontal compositions? Also, have you tried traditional tank development or tray development and if so, do still see this shading when developing by either of those methods? Lastly, I've assumed that the sample image seen above is a direct negative scan. Is that correct, or is this instead a print scan?

N. Riley
http://normanrileyphotography.com