Leica and diopters.....

[DigitalHeMan]

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Today I visited the optician for an eye test. I don't particularly have any issues with my sight, but wanted to have them checked.

 

Basically, the results were that I don't need glasses yet, but my eyesight is becoming slightly negative, so will probably need some +1 readers within a year or two, which is not unusual at this time of life.....

 

But it led me to think about my Leica viewfinder. If I am correct, the M9 has a -0.5 diopter viewfinder adjustment by default, and I was wondering why Leica chose -0.5 if the majority of the population as they get older need + correction, rather than - correction?

 

Should I already be thinking about getting a +1.0 viewfinder attachment to correct my slightly negative vision? Or is it not worth worrying about?

 

Thanks

 

Simon

[wlaidlaw]

Simon,

 

On the basis of my experience, you may find +0.5 is enough, remembering that the virtual image is generated at 2 metres distance. I am only just considering needing to change to a +1.0 after some years with a + 0.5. A friendly Leica dealer may let you try before you buy. Leica Mayfair certainly will.

 

Wilson

[satijntje]

Indeed, try before you buy :-)

 

I'm happy with the -0.5 factory setting, and the additional -3.0 diopter that gives me -3.5 which is perfect for me.

 

John

[Jeff S]

...I was wondering why Leica chose -0.5 if the majority of the population as they get older need + correction, rather than - correction?

 

I'm no optician, but my understanding is that a diopter is the reciprocal of the focal length measured in meters, so (minus) .5 diopters corresponds to the 2m virtual distance of the focus patch.

 

More discussion, including rationale for this distance, is provided here.

 

Personally, I prefer using prescription (sun)glasses, as they provide not only distance correction and sun protection, but also correction for my astigmatism. Since I don't like contacts, and don't like to take glasses on and off to see both the VF and distant subjects (which would be necessary for me to use the Walter diopter eyepiece that also corrects for astigmatism), this is my best solution. But eyes are of course specific to individuals, as is comfort level with various means of viewing and, if necessary, correction.

 

Jeff

[jaapv]

I've one of these dioptre wheels that let you find the optimal correction. If you want you can come by to try it out. I'm out of the country now, but I'll be back in the first week of November.

[DigitalHeMan]

Thanks Jaap, that's very kind. I may take you up on that offer when you return

[tobey bilek]

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you need not remove eyeware. As we age , the eye loses ability to focus close.

 

Generally the answer is bifocals with a + correction in the bottom or readers which are + all over. You will then impair distance vision so they come off and on.

 

When you can no longer focus sharply however the VF is set, it is time to introduse some + correction.

 

If bifocals are worn, then the + is in the bottom is set for reading distance, around 14". It is nearly impossible to see through the bottom in the camera. Solution is to add some +. Eventually all focus ability is lost, then I wear my normal negative correction for distance and overcome it with + diopter on the camera.

 

Or use my Nikons which have built in variable correction.