About the -0.5 diopter of the M11 viewfinder

[Jeff S]

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Agree with everything Jaap wrote before I could.  My 1.25 magnifier has stayed in a drawer for over 10 years.  
 

Trust your eyes, not the mathematics.  If still fuzzy, be sure that you have corrected for any astigmatism.  For decades I was fine just using glasses to correct for astigmatism and distance (and sun glare); only recently having to add a diopter for minor correction due to aging eyes.  

Jeff

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[Besprosvet]

20 hours ago, Jeff S said:

Agree with everything Jaap wrote before I could.  My 1.25 magnifier has stayed in a drawer for over 10 years.  
 

Trust your eyes, not the mathematics.  If still fuzzy, be sure that you have corrected for any astigmatism.  For decades I was fine just using glasses to correct for astigmatism and distance (and sun glare); only recently having to add a diopter for minor correction due to aging eyes.  

Jeff

Only with -0,5 was still (slightly) fuzzy, with -1 looked perfect. Unexpected since my right eye is -0,4ish

[jaapv]

12 hours ago, Besprosvet said:

Only with -0,5 was still (slightly) fuzzy, with -1 looked perfect. Unexpected since my right eye is -0,4ish

It all depends on the accommodation flexibility of your eye. Mild normally irrelevant astigmatism may also influence the result.
A variation of 0.5 is quite normal, reason we advise to try it out instead of following your prescription. 

[jk356]

just to clarify

is the Leica viewfinder lens a +0.50. that makes sense to ensure that 2m is in focus.  This means that a -0.50 over the viewfinder will neutralize this distance and make the viewfinder focus at infinity.  

For instance -if the viewfinder was set at infinity, you would need a +0.50 is focus a 2m.

consider an eye that has no accommodation (cannot focus from infinity to near, such as a person over the age of 65 that needs reading glasses for near vision.  this person will need +0.50 to see clearly at 2m.  

If a person is near sighted and their spectacle correction is -2.00, they will need a -1.50 [-2.00 +(+.50)} Leica correcting viewfinder lens to see the focus patch clearly.

 

if a person is farsighted and has a correction of +2.00, they will need +2.50 [+2.00 +(+.50)] . for the focus patch to be clear

 

if the person can accommodate under age 40, use the nearest distance correction for the Leica viewfinder lens and they will be able to accomadate the +0.50 to make the focus patch clear

Edited April 6, 2024 by jk356
correction