Bronica 500mm S lens issue

[che]

I would be grateful for any input with this issue especially if you have and use a bronica 500mm S lens.

When mounted, my new to me 500mm S lens shows what looks like a vignette parallel to the top edge of the focus screen.
The 3 other edges of the focus screen are sharp to the edge.
after much obsession and testing, it seems that the vignette is the lower edge of the mirror.
with the mirror up, there is no vignette to the film plane.
the vignette is not the internal rear baffle of the lens.
same results with 3 different camera bodies and no sign of this issue with any other lenses, including a 250mm with a 2x teleconverter.
I added an extension tube to the equation and the vignette is now further down the focus screen by about 1.5mm

I don't understand the physics and geometry of this issue, but if i dismount the body, hold it close to the rear of the lens and raise it up, the image circle then fills the focus screen with a sharp edge along the top.

misaligned lens elements? lens shows some scuffs and use, but no dents or obvious signs of damage anywhere
thanks
the second image (1054) shows the mirror almost fully seated during winding but not 100%. As i wind and the mirror moves back in place, i can watch the shadow of the edge of the mirror on the focus screen move up to almost disappear at the edge of focus screen, but not fully, leaving the vignette (edge of mirror shadow)

thanks

 

[MattKing]

That may simply be a consequence of how the viewing system is designed - with very long lenses, you can't see all of the field because the mirror isn't big enough.
The older Hasselblads exhibited the same issue.
If this is the situation, there will be no consequence to it on the film.
Which camera body is this being used with?

 

[wiltw]

Hasselblads had the image cutoff issues with long FL, until Hassy changed the mirror design.

 

[che]

the lens was tested on 2 SQ-a bodies and an SQ-b which all look to have the same mirror. It does seem that there will be no affect on film plane. I held a thin piece of paper up to the back of the bodies and could see the image through the paper. image looks fine. I should just get out and shoot. It would be great to hear from another user of this lens. thanks

 

[MattKing]

Which model are you using it with?

 

[Klaus_H]

Hello che,
I just mounted the S 500 on my SQ A and tested it.
The botton of the 'picture' including the edges are presented sharp.
The top of the 'picture' including the edges is vignetted.
It is a shaddow (about 8% of the 'picture') at the upper border of the focus screen.
I think it is caused by the construction of the mirror. It seems to be too short to work with a 500 mm lens without vignetting.
I got the same results with a SQ b and a SQ Ai body.

It is not a fault, it is a feature.

Klaus


P.S. I remeber some models of Hasselblad did have the same issue.

 

[Sirius Glass]

That may simply be a consequence of how the viewing system is designed - with very long lenses, you can't see all of the field because the mirror isn't big enough.
The older Hasselblads exhibited the same issue.
If this is the situation, there will be no consequence to it on the film.
Which camera body is this being used with?

Hasselblads had the image cutoff issues with long FL, until Hassy changed the mirror design.

I agree. I see the same thing on my Hasselblads, but the problem does not appear on the negatives.