focusing--binocular vs ground glass lupe : LUSENET : Large format photography : One Thread

having recently purchased a used binocular Acra Swiss viewing devise, I'm inqiring if additional "fine focusing" is necessary, ie., taking the unit off & using a lupe on the ground glass------my eye accuity is not as it once was, and I'm doing the additional "fine focusing" just to be sure.. Your comments please.

-- Raymond A. Bleesz (, February 23, 2001


It really depends on what works for you. If you find you're never changing the fine focus when you double-check with the loupe, you can just leave on the binocular device. But if you're always altering the focus when you put on the loupe, then the binocular viewer should just be used for composition.

I usually leave on my viewer for most wide-angle shots and others done in bright light, but when the light falls and/or focus is critical or tricky I unsnap the viewer and put the loupe to the ground glass.


-- Simon (, February 23, 2001.

Raymond: I use the Arca-Swiss binocular viewer, and have tested focusing accuracy with it. In most situations, with adequate illumination, the accuracy of the viewer is no worse than with a 4x loupe. If I am using radical movements, or if the lighting is dim, I will use a loupe. It depends in large part how much of a hurry I am in, but since I find that the light is almost always changing, I prefer to get off at least one or two shots quickly.

The effective viewing distance with the binocular viewers is slightly closer than standard reading distance, so make sure you use the latest prescription. I had my eye doctor add about 0.25 diopter to my reading prescription for this purpose.

I had an opportunity to visit with Martin Vogt, the president of Arca- Swiss last summer. He said that in their experience, focusing accuracy with the viewers was very good. What they have found, with both the viewer as well as loupes, is that focusing accuracy declines the longer you "fiddle" with it. Your first impression, as the image contrast snaps into focus, is the most accurate. The longer and harder you stare, the more your eye begins to compensate for focusing inaccuracy. It reminded me of multiple choice questions, always go with your first answer.

-- Glenn C. Kroeger (, February 23, 2001.

Hello Raymond, I use a similar device and I always check for fine focussing with a 6x lupe. Most of the time, there is a slight correction to be made. I agree, this can be optional in bright sunlight. But we dont shoot much in bright sunlight. Do we?

-- Paul Schilliger (, February 23, 2001.

I believe the binocular viewer has ~2x magnification. If a 2x loupe works for you, then the viewer should be all you need. My eyes need more help than 2x.

-- Larry Huppert (, February 23, 2001.

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