Vignetting 4x5 300mm

[SimonMaddock]

Hello everyone,

Long time reader, 1st time "writer".
I don't know if this is the correct "forum" or even if the question was already posted (I've made a quick search and didn't find anything).

I'm taking the 1st steps with a "new" lens on my 4x5 SINAR norma.
It's a beautiful Rodenstock 300mm f5.6 Sironar-N MC.
(I'm used to wider lenses, as I work manly with architecture)

I'v' already taken a few shots, but the last ones have an horrible vignetting.


I'm guessing this has to do with the image circle and bellows distance but I'm not quite sure how to solve it/ avoid it.
I would like your expertise on the matter before doing a couple of tests, exploring the distance to subject en consequently bellows expansion.

Thank you very much for your advice.

I think it would be helpful if you could share a photo of your lens. The results are not normal