Diopter correction advice

[shimokita]

... there would be no reason to divide the spherical figure in half...

Thanks for the correction Rob, my misunderstanding of the formula.

Casey

 

[Timmyjoe]

Here's how it's worked for me for decades now. I shoot Leica rangefinders, and Nikon & Canon SLR's (older ones). I was told years ago that all the cameras I shoot have a "From the factory" optic of -1.

I need to +1 the optics for my vision (so I need to make the optic "0").

With Leica, their diopters are marked by the optical change, so a +1 is a +1 diopter and when I put a +1 diopter on my Leica, the optic is then "0".

With Nikon and Canon, their diopters are marked for the final optic with the diopter attached. So a "0" diopter in Canon or Nikon adds +1 to the factory optic (-1) and brings the final optic to "0".

What I have found is a Leica +1 diopter is optically the same as a Canon or Nikon "0" diopter. I know this because I have all three, and they are all optically the same.

Hope that helps.

Best,
-Tim

 

[john_s]

Actually, the best we can do is to have an optician grind a lens specifically to your prescription. One would have to take care to see that it is rotated correctly to the prescribed cylinder axis.

Obviously ideal, but with a rectangular format camera, when turning the camera 90 degrees to go from landscape to portrait you would be worse off. There was a self-rotating eyepiece device advertised a few years ago which would have solved the problem.


An argument for square format.

 

[Rob-F]

Here's how it's worked for me for decades now. I shoot Leica rangefinders, and Nikon & Canon SLR's (older ones). I was told years ago that all the cameras I shoot have a "From the factory" optic of -1.

I need to +1 the optics for my vision (so I need to make the optic "0").

With Leica, their diopters are marked by the optical change, so a +1 is a +1 diopter and when I put a +1 diopter on my Leica, the optic is then "0".

With Nikon and Canon, their diopters are marked for the final optic with the diopter attached. So a "0" diopter in Canon or Nikon adds +1 to the factory optic (-1) and brings the final optic to "0".

What I have found is a Leica +1 diopter is optically the same as a Canon or Nikon "0" diopter. I know this because I have all three, and they are all optically the same.

Hope that helps.

Best,
-Tim

I believe this is exactly correct.

 

[Rob-F]

Obviously ideal, but with a rectangular format camera, when turning the camera 90 degrees to go from landscape to portrait you would be worse off. There was a self-rotating eyepiece device advertised a few years ago which would have solved the problem.


An argument for square format.

Oh, yes, I had not thought about that. Best to go with the 1/2 cylinder correction, then.

 

[shimokita]

Oh, yes, I had not thought about that. Best to go with the 1/2 cylinder correction, then.

Hahaha... does that mean Post #8 is back in play ... just kidding

My prescription is cylinder -0.5 and sphere -1.75
[edit: revised calculation] diopter = 1/2 x (cylinder + sphere)
my prescription calls for a -1.125 adjustment
which according to the chart (Post #8) is a -2 Nikon marked lens
... and that's the Nikon Diopter that works for me