I shot this long exposure(either 2 or 4 seconds) at about 4:30 in the morning as the sun was rising. I didn't realize until I had scanned and edited the photo that it had some vignetting on it. Is this normal? I was using a Bronica SQ-A w/ Bronica PS 110mm macro...any insight on this? I'm not too worried as vignetting can be fixed in photoshop, just curious.