Rangefinder, diopters, and farsightedness

[Mike Anderson]

I don't know much about optics but I know I need a +2.5 reading glasses to read and with (Nikon) SLRs a +1 diopter adjustment seems to work well for me. I don't understand the theory but I've found +1 diopters work for me with SLRs.

When I use 35mm rangefinders it's very blurry if I'm not wearing reading glasses so I hardly use 35mm rangefinders. I've rigged up thing like taking a lens of old reading glasses and taped it to the rangefinder and that makes it usable but clunky.

Looking at images on ground glass is fine because the loupe I have has a diopter adjustment.

I'm trying to figure out what kind of diopter technology I can use for rangefinders, specifically a rangefinder like a Kalart that might be attached to a press camera. A search for "Kalart diopter" yields nothing useful. How the heck do farsighted people deal with rangefinders?

...Mike

[Paul Bujak]

I wear my regular glasses with my rangefinders and when I am finished, I wash the eyeball grease off the lens.

[Steve Goldstein]

It all depends on the optical design of the viewfinder. I recall reading a long time ago that the viewfinder of one brand of 35mm SLR (I forget which) was designed to "appear" to be about 30" or 36" away. In this case +1 would be about right as it would take infinity-corrected vision to a distance of 1 meter.

I've done this experiment with my Mamiya 7. My "computer work" glasses are +1 relative to my distance prescription. After a lot of back-and-forth I'm satisfied that I'm better off with my normal prescription, so for the M7 at least, the image seems to appear at infinity.

I don't know what range of diopters you can get in reading glasses commonly sold in drug stores, but you could bring your camera in and check them out at no cost. Alternatively, bring it next time you have a refraction (eye exam) performed.

[Mike Anderson]

It all depends on the optical design of the viewfinder. I recall reading a long time ago that the viewfinder of one brand of 35mm SLR (I forget which) was designed to "appear" to be about 30" or 36" away. In this case +1 would be about right as it would take infinity-corrected vision to a distance of 1 meter.

I've done this experiment with my Mamiya 7. My "computer work" glasses are +1 relative to my distance prescription. After a lot of back-and-forth I'm satisfied that I'm better off with my normal prescription, so for the M7 at least, the image seems to appear at infinity.

I don't know what range of diopters you can get in reading glasses commonly sold in drug stores, but you could bring your camera in and check them out at no cost. Alternatively, bring it next time you have a refraction (eye exam) performed.

I have a Canonet and with that my normal reading glasses (+2.5D) makes the image and focusing clear. But that's not a very usable setup, having to carry reading glasses and putting them on for focusing, take them off in order to walk without tripping.

If I do get a rangefinder press camera I might try and rig something so it can take Nikon screw in diopters since I have a few of those, and they're cheap and available.

...Mike