focusing--binocular vs ground glass lupe

[raymond_bleesz]

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.

[simon_gammelin]

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.

 

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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.

 

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.,.,.,.,

[glenn_kroeger]

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.

 

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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.

 

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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.

[alpshiker]

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?

[larry_huppert1]

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.