Please see the attached screenshot of the preview scan from the scanner. I'm seeing a dark band down the center of the negative, running the length of the film. Not sure where I should start looking to eliminate the problem. Light leak somewhere? Chemical problem? This is not the first roll I've seen this, but it's not consistent, and has happened with 2 entirely different cameras. I'm doing something wrong somewhere. Hasselblad 500C/M, HP5+ in D76 1:1 for 12 minutes. Reasonably fresh chemicals. Thanks for any suggestions.