4x5 light leaks?

I received these two transparencies back from my normal lab this week with what appear to be light leaks on both. I am a relative beginner and have only been making LF photos for about 18 months but never had this problem before.
These shots were taken with my new Intrepid 4x5 but I pretty sure it isn't a camera fault because I took the same views with different types of film at the same time. I am using used Fidelity Elite film holders. I have 8 of them and they appear to be in reasonable condition. I have a knotch code on the film holders so I can see which holder was used and both of them have been used before without problems. I can't see any obvious faults on these holders. There are no splits or cracks on the dark-slides and no gaps in the slots around the holders. I'm also pretty sure the film was loaded correctly. The only nagging doubt I have is the length of time the transparency film (Velvia 100) was in the holders. I don't shoot much colour and these films were in the holders for several months.
I am going to take some test shots today with these holders with B&W negatives and develop them tomorrow. Someone with lots of LF experience has suggested this might be a processing error but I haven't gone back to the lab yet because I want to get my facts straight.
I have a big overseas trip coming up and I want to get this sorted out ASAP. Nothing worse than worrying about equipment failure or if I'm doing something wrong. Anybody had problems like this before and what advice can you give me? Thanks.

I looks like a light-leak to me. You can see that in both cases the light leak was from the flap end of the filmholder (i.e., not the darkslide/light trap). I would examine your holders for defects in this area just to be sure, but it may not (probably isn't) the holders, especially if the photos you posted were from two different holders.

Most likely, you have a defect or seating problem in the camera back. Insert a holder and examine closely the area that leaked for any grooves, holes, unevenness, etc. that might cause this. A flashlight from the opposite side while you're examining the back may illuminate the problem.

Some things to consider:
Have you shot other photos with your new camera without this problem? Where was the sun when you took these photos? Any chance of dirt or debris being part of the problem?

Good luck finding the leak,

Doremus

Thanks Doremus and Ian for your replies. I made test photos using the offending holders yesterday and developed the B&W negs this morning. No problems at all this time! Here are some iPhone pics of the holders. I'm baffled... I don't like mysteries and I like intermittent faults even less...

I am willing to bet you did not keep your dark cloth over the holder and camera at all times.That would solve the problem.

Thanks for the input. You are right, the dark cloth wasn't on the camera or covering the film holders all the time. I think this must be a case of the holders being subjected to too much direct sunlight. I will run another test soon and be more careful in future.

The fact that the rebate is exposed points to the problem being outside the holder. It is possible the lab did it, or you had a pinhole in the bag you stored the film in before/after exposure.

Thanks Patrick, I see what you mean about the origin of the leaks. I don't think my film handling is at fault because I use a proper changing tent and always put the exposed films into the original film boxes. I will have a chat with the lab tomorrow.

Read this:

http://www.largeformatphotography.i...p?138269-Stop-Light-Leaks-Use-your-dark-cloth

If you are not yet a member then you should also join Large Format Photography Forum. A lot of us APUG members who shoot large format are members there as well.

is it possible that the holder was slightly pulled away from the back of the camera when drawing out the darkslide? it has happened to me a few times.

Agree with monst. Film and film holder handling can be have inconsistencies, which lead to light leaks. When I insert the holder into the spring back, I check to be sure it is seated flat against the camera back, and that the spring back is flat against the film holder, and that the film holder is inserted fully/not too deep. The camera back > film holder > spring back sandwich needs to be parallel and flat. Normally anything improper here is due to the operator inconsistency.