4x5 sheets with a white "triangle"

[ibandera]

Hi!

Today I was developing at home for the first time and I noticed that some of the negatives are having a white triangle on them.
All of them have been taken with the same lens, 105mm f8, the negatives taken with a different lens are fine.

What could be the problem with the lens? Maybe the blades aren't closing properly after shooting.

Thanks!

[djdister]

Not a lens problem. You have fogging of the film from light leaking around a badly seated bellows or lensboard perhaps.

[ibandera]

Thanks!! you are right, I did a check now and there was some light coming from one side of the lensboard