M10 Correction lenses

[Tanndoktorn]

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Hi!

Can anyone explain why Leica has chosen -0.5 as default optical correction in the OVF on the M10?

Are Leica users all wearing -0.5 glasses??

I'm using +1 glasses. According to Leica I should then use a +1.5 correction lens. Why not -0.5 +1 = +0.5 ?

When I use my +1 glasses seeing through the OVF, I see perfectly clear.  Why should I then buy a +1.5 correction lens and not a +1 correction lens?

 

Cut from Leica:

The Leica Correction Lenses M provide optimum eye-to-camera matching, making composing images in the viewfinder more precise and comfortable. They are available in grades of +/- 0.5, 1, 1.5, 2 and 3 diopters. Please note that the Leica M-Viewfinder is preset by default to -0.5 diopters, so anyone wearing glasses of 1 diopter strength would require a +1.5 diopters correction lens.

Edited January 24, 2019 by Tanndoktorn

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vor 8 Minuten schrieb Tanndoktorn:

...When I use my +1 glasses seeing through the OVF, I see perfectly clear.  Why should I then buy a +1.5 correction lens and not a +1 correction lens?

Did you check it with +1.5 too?

On the other hand, if you feel fine with a +1 correction, take that one

[a.noctilux]

Hello,

Since M3 from 1954, the -0.5 correction in VF was choosen I think that was from "market study" by then.

Nothing changed since then..

Just backward move from LTM Leica which had continous diopter correction for rangefinder.

Not so simple as math to see clear in M's VF.

Best way to sort it out first time is to go to a Leica Store to try the diopters and some people just use the M with their glasses.

[Jeff S]

I wear glasses to correct for astigmatism and for distance.  But I found by using free trial diopters at a local optician that adding a +.5 diopter (still with glasses on) optimized focusing on my M10.  Years ago, with younger eyes and a different M, no diopter was needed.  

Easy to try... the only way to really know.

Jeff

[Tanndoktorn]

Thanks, I was interested in the history and the math. I know how to solve the problem by trying different lenses 🙂

[Jeff S]

The focus patch is set at a virtual distance of 2m, so ideally one needs to see that clearly, as well as have enough eye accommodation to see the background clearly, which appears actual distance.  Eyeglass prescriptions vary for all kinds of circumstances, so one simple solution rarely fits all.  

Somewhere here others have written about the logic of the default -.5 setting.  I don’t recall the specifics, but someone will likely chime in.  Leica has obviously determined that this provides the best viewing for those with ‘normal’ vision, without resorting to aids, glasses or diopters.

Jeff

[Jeff S]

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I found what Leica has written....

 Please note that the default value of the viewfinder of the Leica M is –0.5 dioptres to guarantee a comfortable view through the viewfinder at medium distances.

Jeff

[mirekti]

On 1/24/2019 at 1:04 PM, Jeff S said:

I wear glasses to correct for astigmatism and for distance.  But I found by using free trial diopters at a local optician that adding a +.5 diopter (still with glasses on) optimized focusing on my M10.  Years ago, with younger eyes and a different M, no diopter was needed.  

Easy to try... the only way to really know.

Jeff

Does one need to buy an adapter thread for M10 in order to put the diopter?

EDIT: Please ignore this, I found it on Leica web page.

Edited January 15, 2020 by mirekti
Silly me

[Jeff S]

39 minutes ago, mirekti said:

Does one need to buy an adapter thread for M10 in order to put the diopter?

EDIT: Please ignore this, I found it on Leica web page.

Better to buy the new diopter specifically made for the M10.  This will provide better viewing as intended with the larger diameter VF, which offers higher magnification and better eye relief.  

Jeff

[mirekti]

14 minutes ago, Jeff S said:

Better to buy the new diopter specifically made for the M10.  This will provide better viewing as intended with the larger diameter VF, which offers higher magnification and better eye relief.  

Jeff

Right, that’s what I meant, I found on Leica site there are M10 version released.

[Jeff S]

11 minutes ago, mirekti said:

Right, that’s what I meant, I found on Leica site there are M10 version released.

Good... they also make adapters for the prior, smaller diameter ones... avoid IMO.

Jeff

Edited January 15, 2020 by Jeff S

[01af]

Am 24.1.2019 um 20:33 schrieb Jeff S:

The focus patch is set at a virtual distance of 2 m [...] others have written about the logic of the default -0.5 dpt setting.  I don’t recall the specifics, but someone will likely chime in.

So you know the answer but aren't aware of it: -0.5 dpt = -2 m.

The framelines in the viewfinder are just an inch or two from your eye physically but appear as if there were 2 m/6 ft away. So the eye-piece's optics is -0.5 dpt.

.

vor 6 Stunden schrieb Jeff S:

... they also make adapters for the prior, smaller-diameter [correction lenses] ... avoid IMO.

While it is preferable to use the new correction lenses which fit the M10's eye-piece immediately, the older and smaller correction lenses on the eye-piece adapter are working just fine. In particular, there's no obstruction or narrowing of the filed-of-view.

Edited January 15, 2020 by 01af

[dickgillberg]

I just bought a correction lens for my M10P. -1.5 like the prescription for my right eye. It works beautifully for distances from about 1.5-2 m to infinity, but not as good for closer distances. Might be my old eyes doesn't work as they should.

[Jeff S]

3 hours ago, dickgillberg said:

I just bought a correction lens for my M10P. -1.5 like the prescription for my right eye. It works beautifully for distances from about 1.5-2 m to infinity, but not as good for closer distances. Might be my old eyes doesn't work as they should.

One needs to account for the built-in diopter correction discussed above. See Rick’s comment in this old thread..

Better yet, experiment first with a diopter at your Leica dealer, or use a free trial diopter at your local optician.  Seeing is believing.

Jeff

[Jeff S]

4 hours ago, 01af said:

While it is preferable to use the new correction lenses which fit the M10's eye-piece immediately, the older and smaller correction lenses on the eye-piece adapter are working just fine. In particular, there's no obstruction or narrowing of the filed-of-view.

Maarten wrote in a prior discussion that the glass in the new diopter was larger in diameter than the old glass.  I haven’t verified,  but if so, it would seem that it might provide some viewing benefits, although I recognize that the focus patch is centered. But it’s always risky to assume.  I tend not to like adapted solutions (even lenses) when there is a more direct, native design, but that’s a personal bias. 

Jeff