What diopter do I need (or want) for my M9?

[Your Old Dog]

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I just had an eye test and have my script in front of me. Either with or with out glasses I do not see the two squares as clearly as I think I should. How can you tell what diopter you would benefit from? When do you go with - and when do you go with +?

 

My normal script is OD sphere -75 Cylinder -50 Axis 090 prism none Add 150

OS sphere -75 Cylinder -100 Axis 090 prism none Add150

 

I shoot left with the left eye which is wierd because I'm right handed so I always have nose grease on the lcd to wipe with my thumb!

 

 

thanks for any help or suggestions (keep in mind, going back to the doctor is a big pain)

[Gary I]

My last exam a few months ago showed I needed a -3 diopter correction in my right "shooting" eye. I am near sighted. The research I did when looking for a M9 diopter correction lens showed that the M9 has -.5 diopter built in. So technically I needed a -2.5 correction lens which Leica does not make to the best of my knowledge. I tried a -3 and it works great. I have tried contacts and eyeglasses with my M9 with inconsistent focus accuracy. For me the diopter correction lens did the job. I can even focus my 75mm Summicron!

 

A word of caution. I found while taking a long walk with my M9 the correction lens can come loose as I lost mine. Luckily I found a used one on eBay for a decent price to replace it.

[jaapv]

http://www.l-camera-forum.com/leica-forum/leica-m9-forum/130720-m9-faqs-frequently-asked-questions-answers-2.html#post1938741

[Your Old Dog]

Thanks for the post Gary and welcome to the forum, hope you enjoy your stay.

 

What is the process short of just buying these diopters to see what's going to be better for you? That's what has me confused. I don't know whether to start with the plus or minus diopters. I suppose I can buy several on ebay but they are pricey and then I'd have to sell the ones I didn't need. There must be some formula protocol for figuring it all out?

 

Thanks for the - (.)5 diopter already in the M9. It would have taken me awhile to figure that out.

 

All the best and happy shooting

Ray..............

[Your Old Dog]

Jaap, thanks a lot for the info. I'll try the reading glasses at the drugstores and see if I get lucky. That's a big help.

 

ray..........

[JT07]

This worked for me, might be worth a try if you haven't already. I simply called my eye doctor and told him what I was looking to do. He checked my chart from my most recent visit and he told me which diopter to purchase. Took him all of 20 seconds maybe. Good luck.

[jaapv]

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Yes and no. The mathematical approach can work, but there are many cases that users get better results from a diopter that has a different value from the theoretical one. The reason being that the markings in the viewfinder are at a virtual 2 m distance and the subject matter, which must be seen sharply in order to focus correctly, can be at any distance. The system brings everything within an acceptable DOF for the average human eye, but if a correction is needed one needs to find a compromise that only can be determined experimentally.

[elgenper]

I just had an eye test and have my script in front of me. Either with or with out glasses I do not see the two squares as clearly as I think I should. How can you tell what diopter you would benefit from? When do you go with - and when do you go with +?

 

My normal script is OD sphere -75 Cylinder -50 Axis 090 prism none Add 150

OS sphere -75 Cylinder -100 Axis 090 prism none Add150

 

....

 

Since you need a substantial cylindrical correction (meaning astigmatism), no diopter is going to cut it for you without your own glasses on. Even if someone made a special lens that would work for horizontals, it would be twice as bad as no lens for verticals...(I had one such lens custom made for my Hasselblad once, but the Hassy image was square, so one never had to turn the camera).

 

There is someone who sells special diopters with rotating lens that should work (I forget the name, but it has been discussed here recently).

 

Your left eye astigmatism is only half of that for your right eye, which may explain your preference for left eye shooting, btw.

 

FWIW, I have rather strong astigmatism myself, and at my age (70) need varifocals. I shoot my M9 with these on, and have no problems.

[Your Old Dog]

Thank you Per,

I'll see how far I get with the drugstore reading glasses and if that don't work I'll just use my poor eyesight as an excuse for my out of focus shots, either that or shoot everything at f16.

 

Thanks for your help, it may save me a lot of fruitless searching.

 

Ray........

[}{B]

I picked up a used +1.5 diopter lens yesterday and it has made focussing so much easier. I would recommend trying before buying though if at all possible.

[Jeff S]

Having astigmatism, I prefer keeping my glasses on, which allows me to both focus properly and look around me to more clearly find photo opportunities in the first place. And, since my eyes are sensitive to outdoor light, I usually stick to prescription sunglasses. Fortunately, my correction suffices without use of a diopter. YMMV.

 

Jeff

[Gary I]

Thanks for the welcome to the forum Ray. What I did to determine my diopter needs was just explain what I was doing to my optometrist and he told me what my diopter correction was. Then just did the math including the -.5 built in to the M9. Since I only needed the -2.5 technically I was afraid the -3 would be too strong but it worked out for me. I had tried magnifiers in the past but found the diopter correction lens worked best for me. Hope you find one that works for you.

 

Gary

[jaapv]

Common misconception: to work the -0.5 into the equation. It is there for a reason: easier accommodation to middle distances for a 20/20 eyesight. So when you calculate the correction for your eyes, the end result should be -0.5 again. But do check with a test lens, as simple theory is not always a substitute for reality.