How can I use a camera viewfinder comfortably with astigmatism and avoid apparent misfocus?
Asked 1/31/2016
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I wear glasses for astigmatism, and when I shoot through an optical viewfinder my vision seems to go out of focus very quickly. This happens whether I wear my glasses or not, especially when closing one eye and using the other at the finder. It makes it hard to judge focus and review images on the camera, even though the files later look unusable on the computer. Is this a common problem, and are there ways to make viewfinder use easier or more accurate for someone with astigmatism?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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Although cameras often have diopter correction, your problem may be due to the astigmatism issue, for which there is no simple adjustment. However, if the viewfinder eye-lens is removable, a custom lens can be ground to correct for your astigmatism. Another possibility is to have such a lens made to overlay a non-removable eye-lens, but you would probably have to work together with an optician willing to experiment. An overlay might also restrict the field of view, though not as severely as do glasses. Note that the corrective lens is asymmetric and must be correctly oriented (or orientated when in GB).
BTW, I've noticed the same issue you describe, particularly after using a microscope or telescope for lengthy periods. Microscopists are taught to keep both eyes open and to ignore the view from the eye not looking through the microscope to avoid eyestrain. Alternatively, the ambidextrous (and ambiocular?) microscopist can look at paper with the off-eye to make a "tracing" of what's under the microscope. This may not be practical in photography, though, where a bright sunlit view would distract from that through the viewfinde.
Originally by user35542. Source · Licensed CC BY-SA 4.0
user35542
10y ago
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Yes—this can happen, especially with astigmatism and when using one eye at the viewfinder for extended periods. First, make sure the camera’s diopter adjustment is set correctly for your eye before shooting. That adjustment can help with normal vision correction, but it may not fully correct astigmatism.
If your camera has a removable viewfinder eyepiece, another option is a custom corrective lens made for the finder. An optician may be able to make a lens or overlay matched to your prescription, though it must be oriented correctly and may slightly reduce the visible field.
A practical technique is to keep both eyes open instead of closing one eye tightly. People who use microscopes and telescopes often do this to reduce eye strain and the rapid “defocus” feeling.
If images look sharp in the finder but soft later on a computer, don’t rely only on what your eye sees through the finder until the diopter is properly adjusted. Set the diopter carefully first, then evaluate focus again.
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