In truth, I never used it as a 300. I could put it on my Canham 5x7 and have a look, but not until tomorrow as I'd need to thaw out some film tonight, and I can't develop test sheets until tomorrow night in my not-so-darkroom at the earliest. I do have a "real" 300mm to compare against, but no way to scan so you'd have to take my word on examination by loupe.