Is this a development problem or light leak?

[MikeS]

What brand of film holders are you using? I ask, because if you're using Linhof brand film holders, they load slightly differently than 'normal' film holders. Also, are you using 'newer' plastic film holders like Fidelity, or such, or if you're using older wooden Graflex brand film holders, that can make a big difference. It's fairly normal for a film holder to have a slight amount of play right to left even when it's sitting against the camera back properly. Do you have your film holders marked so you can tell which holder the fogged film came out of? Is it always the same one? If you don't have your film holders marked, I would suggest that you mark each one with either a notch code, or a number on a small piece of film mounted so it marks the film, such as the ones in the images attached to this message. Once you have a way to tell which film holder is fogging the film, you can go further to investigate the fogging.

[mikestr]

Did you ever solve this mystery? Assuming you haven't, I would check to see if this is the result of an incompletely inserted film holder. With many 4x5 spring backs it is necessary to give an extra shove to get the holder past the last "ridge" so that it's in all the way. Take Ken's advice regarding the need to squeeze the focus panel and rear standard when removing and inserting the dark slide so you don't all move the camera at the same time. I always check the far end of the holder after insertion to see if it's flush with the frame of the camera back. If not I will have a light leak when the dark slide is pulled. In your example I might also suspect that the holder is not lying flat and perpendicular to the lens axis, as the bottom of the image is so much less focused than the middle (lower arms v shoulders) even though the image appears to be taken straight on (this could however be the result of a tilted lens standard. This can also be the result of an incompletely seated holder. Ignore the comment about the tape on the flap: It serves only as a hinge and has no light-sealing function; the flap is designed as a light trap.