Light leaks on 4x5 negatives

Hello everybody,

Today was the first time ever getting back my 4x5 film developed from the lab.
Very pleased of the result at first, I started to notice some bad light leaks from both the down corners of the film.
It seems to be the same source in every negative which makes me think the problem aren't the holders but I can't explain why I'm getting this problem (the lens, the box during the trip to the lab, the camera,.... ).

Does any of you here more experienced than I am have an idea of what is going on ?

The gears used for the shoots are :
Sinar P
Schneider Kreuzach Super-Angulon 120mm F8
Kodak Portra 160

Thanks in advance for any reply,
Best regards,

Pierrick

Holders were not seated correctly in the camera back.
The lock rib was not in the lock rib grove. This makes the holder at the lock rid stick out 1/16 of an inch.

Very often, the photographer pulls the spring back away from the camera body when pulling/inserting the darkslide. The solution is to pinch the spring back to the camera body when doing this.

As Richard points out, you should also make sure the holder is seated correctly (before pulling the slide).

Also check to see if there is any light baffling material that may be missing and causing the leaks.

Best,

Doremus

I once developed a light leak with my Sinar Norma that was caused when the light baffle in the camera back was letting loose near its trimmed end at the corner of the back, and it had doubled back over itself thus becoming twice its thickness locally at the corner. The film holder could not then lay flat against the camera back. Fortunately I had previously bought some extra baffle material from Sinar just in case I ever had a problem, so I replaced the baffle entirely and have never had an issue afterwards. I don't know if the Sinar P is the same as the Norma, in which the baffle material is glued into a shallow groove that's about 1/8-inch wide.

Another thing you might do...looking at the negs that the leak is on top, you might after you finished focusing on the ground glass is to cover the bellows and camera itself with your focus cloth to make sure no chance of light coming in.