Quote Originally Posted by Xander Fischer View Post
I'm talking about barrel distortion that causes verticals/horizontals to bow or bend. I've read that some 300mm lenses do exhibit some barrel distortion, and given that I shoot a lot of subjects with strong vertical/horizontal lines, I want to be sure that I'm getting the lens with least distortion.
Be careful what/where you read. I've used and owned 300s from turn-of-the-last century Goerz Double Anastigmats to modern Symmar-S Schneiders, and have yet to see noticeable barrel distortion from any of them.

Also, be wary of lenses with huge image circles, they can cause bellows flare. A 12" Red Dot Artar would be very sharp, distortion free, with superb color balance and still have a large enough image circle for movements on 4x5.