Sinar reflex housing focus problem

[Vic Carson]

I’ve come across a problem with the Sinar binocular reflex housing that I’m wondering if anyone has any experience with.

I’ve just started using one and discovered that what I shoot with it on isn’t sharp. After comparing it with the focus obtained from a loupe on the ground glass, it appears the housing impairs the focus by -3, based on the Sinar rotating dial scale. So if the focus obtained through the loupe on the ground glass is set to 0, then the focus for the reflex housing comes in at -3 on the scale. The difference appears to be even across different focal lengths of lenses and differing subject to camera lengths. And the housing impairs focus in the same way when the magnifying lenses are flipped up or down. It's possible the explanation could involve the mirror, but this housing appears to be in good original shape.

I’m wondering if anyone has experienced this problem and perhaps found a way to solve it.

Cheers,
Vic

[mikec]

Vic,
I have a model P and just had a check with mine and found no issue. After focusing with a loupe,focusing remained spot on with the reflex on, magnifiers up or down, or after pivoting of the mirror. Do you wear glasses?
I do notice that I get better focussing, even when using my Schneider x4, when I have the right pair on :) . Maybe all you need is a trip to the opticien.

[W K Longcor]

I've used one of these viewers for a long time and never really had any problems -- at least not with the focus of the camera. I would think ( and Anybody with a better knowledge of optics may correct me) , that the reflex viwer is just giving you a reflection of the actual ground glass image -- if the image on the ground glass is NOT sharp, no amount of magnification, reflection or shift of the VIEWING optics is going to make it look sharp. Is it possible that something is a little loose on the rear standard of your camera -- and the added weight of he viewer is promoting a shift or movement when you open the back to insert the film holder?

How about focusing on a subject with your loupe and a dark cloth, then -- with everything locked firmly in place -- clip on the viewer and see if there is a shift?

I'd say that that was my 2 cents worth -- but it's probably only worth half that.:D

[Peter De Smidt]

Different diopter magnifiers are available for the Sinar viewer, I seem to remember. Perhaps you have one that's not compatible with your eyes? The lens unit, the part that flips in and out of the viewing path, should have a part number on it somewhere. When you find it, you could then contact Sinar, or perhaps Bob Watkins at Precision Camera Repair to see what rating it is. Either of these should be able to help you out.

[Vic Carson]

Thanks for your insights.

I had actually wondered if the difference in focus was attributable to the monocular use of a loupe as opposed to the binocular use of the reflex housing. But using the loupe with my non-dominant eye, or using the reflex housing in monocular fashion yields exactly the same result.

I also considered the problem mentioned by WK Longcor, where looking into the viewer, if pressure is put on it, tilts back the ground glass, altering the focus. But this isn’t the source of the problem either.

I suppose the next step would be to compare it with another reflex housing, or to see if the results I’m getting hold for someone else, although I’m not sure why they wouldn’t. I can get the image as it appears in the reflex housing sharp, it’s just sharp at a slightly different bellows extension.

One way or another I need to figure it out, or else get ready to throw my hat in with the legion of shooters whose battle cry is “it looked sharp at the time”.