Movements and their effect on film frames

[bwakel]

I recently built up a Linhof Technika 6x9 from bits acquired over eBay. I've got a Technika III body, Schneider Super Angulon 65 5.6 lens and a 6x9 Super Rollex back. I just got my first roll of Velvia back from the lab and I've got what appears to be a problem.

The first image is stunningly sharp and I'm really impressed with the film flatness of the back and the sharpness of the Super Angulon - it appears sharper than my Mamiya 7 lenses which amazed me. However, on the second shot I used a combination of lift on the front standard and full tilt on the back (just to see what happened - I've never had movements before!) What appears to have happened is that the frame has extended from 84mm for the other frames on the film to 90mm and the top of the image has exposed on top of the bottom of the first frame (the image was exposed in portrait rotation).

Has anyone come across this issue before? I assume it's because the frame isn't actually masked on the back and the extreme tilt on the back has thrown the image over a greater area of film. Anyone have any experience of how much rear movement I can get away with? Are there any other gotchas that I ought to be aware of before I expose my next roll of film?

Thanks

Barry

 

[roteague]

With back tilt you rarely need more than a couple of degrees or so of tilt.

 

[Dan Fromm]

See if you can look at another Super Rollex. Sacrifice a roll of film to check that yours is giving correct frame spacing. Also make sure that you withdrew the dark slide far enough.

No roll holder in good order should let the user expose any part of a frame more than once.

 

[mortimer]

I had a similar problem when I first picked up a Mamiya Press 23, the spacing was off. It was explained to me that modern film emulsions are a bit thinner (not sure if that's true or not) and to wind the start arrow an inch past the marker in the back, everything's been spaced perfectly ever since.

BTW, I picked up a 6x7 Linhof III half a year ago, and it's absolutely outstanding. If you get a chance to pick up a 240 tele arton, do it - sharpest tele I've ever used.

 

[crispinuk]

Hello Barry,
I've had another one of my random thoughts:
Your mention of the back being in portrait might be the clue. I'm guessing there must be some sort of mask on the holder, but how close is it to the film, and is there a gap at all between them ? Without back tilt the light will hit the film perpendicular, but with a lot of tilt the light will be arriving at an angle so could 'go under' the edge of the mask, the front rise might have also contributed to this. The combination of the fulcrum of the tilt not being central and the rise could explain why only one side of the frame overlaps.

Or perhaps not.

Crispin