Post by Stephen on Nov 10, 2012 16:56:24 GMT -5
I have an older Tokina wide angle 17mm F3.5 lens, which was made for OM mount, but although it was optically OK, the mechanics were a bit poor, and the auto diaphragm was not working properly, so it was duly stripped down to repair.
But as I am short of a good really wide angle for the Exakta cameras, and repair to the OM mechanism proved difficult, broken lever internally, I decided to look at the feasibility of conversion to Exakta mount, with manual diaphragm only.
Fortunately the lens defaults to manual aperture operation once the sprung OM mount was removed, and there is enough space to make an adaptor, by dropping out the OM mount and replacing with Exakta.
I have a spare Exakta mount, in brass, from an old tube set, which can be machined to fit, with a spacer to adjust the infinity focus. Because the Olympus body is thick and the film to flange distance is far greater than Exakta there is plenty of space to add a lathe turned spacer in aluminium. Final adjustment for focus can be done with very thin paper shims.
With 17mm focal length, the depth of field is large, to say the least, the Tokina is a retrofocus design, and being only F3.5 means the back element is small and the lens will also work on the Exa, and the element clears the mirror shutter, which vignettes some lens.
Stephen.
But as I am short of a good really wide angle for the Exakta cameras, and repair to the OM mechanism proved difficult, broken lever internally, I decided to look at the feasibility of conversion to Exakta mount, with manual diaphragm only.
Fortunately the lens defaults to manual aperture operation once the sprung OM mount was removed, and there is enough space to make an adaptor, by dropping out the OM mount and replacing with Exakta.
I have a spare Exakta mount, in brass, from an old tube set, which can be machined to fit, with a spacer to adjust the infinity focus. Because the Olympus body is thick and the film to flange distance is far greater than Exakta there is plenty of space to add a lathe turned spacer in aluminium. Final adjustment for focus can be done with very thin paper shims.
With 17mm focal length, the depth of field is large, to say the least, the Tokina is a retrofocus design, and being only F3.5 means the back element is small and the lens will also work on the Exa, and the element clears the mirror shutter, which vignettes some lens.
Stephen.