Confused about diopters

[T25UFO]

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The Leica M has a default setting of -0.5 and I have been using a diopter of +1.5.  I think that makes my eyesight setting of +1.0.  Correct?

I recently purchased the SL3 and the manual says this has a default setting of -1.0 with adjustments from -4.0 to + 2.0.  To see the readout clearly I turn the ring to the left - see photo.  Unless I' being really stupid and reading this wrong, the diopter setting would appear to be -2.5.  How can this be?  Am I missing something here?  

Advice please.

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[RobW0]

36 minutes ago, T25UFO said:

The Leica M has a default setting of -0.5 and I have been using a diopter of +1.5.  I think that makes my eyesight setting of +1.0.  Correct?

I recently purchased the SL3 and the manual says this has a default setting of -1.0 with adjustments from -4.0 to + 2.0.  To see the readout clearly I turn the ring to the left - see photo.  Unless I' being really stupid and reading this wrong, the diopter setting would appear to be -2.5.  How can this be?  Am I missing something here?  

Advice please.

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Could it possible have something to do with the effective viewing  distance of the viewfinders? I see the SL camera says something about 21mm exit pupil distance. I can't find the number right now but I though the M viewfinder was something like around a 2m effective viewing distance. I could be completely off base with this explanation.  

[Marc B-C]

I am not an SL3 owner so cannot help but does it matter where the ring turns to? Surely it only matters that you see the readout clearly?

[T25UFO]

Correct, but curiosity lingers.  I would just like to know why the values are seemingly opposite.

[elgenper]

The "default of -0,5" I interpret as a distance of 2 m to the virtual images of the frames and RF patch in the M finder.  So whatever you need to see clearly a poster or similar hanging 2 m from you should work well when using the M finder (the actual subject is seen through clear glass, just like a window).  The info in the manual is plainly misleading.  The only secure way to find your correction is to try diffferent powers (can be easily done at a dime store stall for selling cheap reading glasses:  try them when looking through the camera finder, find one that makes you see clearly, note its power, and then order that Leica diopter).

For myself, after having both my eye lenses replaced in cataract operations a few years ago I have excellent distance vision, in good light down to less than 2m.  So, I use my M11 without any diopter; works perfectly that way.  My reading glasses are +2; for work at my 30" Apple monitor, +1 is what I need.

Edited December 15, 2024 by elgenper

[jgeenen]

if you compare the scale in the manual with the turning directions in the image next to it, it seems that the manual editors might have just reversed the scale on error. Sh* happens.

[Photoworks]

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4 hours ago, T25UFO said:

The Leica M has a default setting of -0.5 and I have been using a diopter of +1.5.  I think that makes my eyesight setting of +1.0.  Correct?

I recently purchased the SL3 and the manual says this has a default setting of -1.0 with adjustments from -4.0 to + 2.0.  To see the readout clearly I turn the ring to the left - see photo.  Unless I' being really stupid and reading this wrong, the diopter setting would appear to be -2.5.  How can this be?  Am I missing something here?  

Advice please.

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that looks like  -2.5 

i think the 2 cameras are different.

My SL camera are set +0.125

My M11 takes the -1.5 lens

My glasses have -0.75 correction, but I don't use them with my camera

[T25UFO]

5 hours ago, Photoworks said:

that looks like  -2.5 

i think the 2 cameras are different.

My SL camera are set +0.125

My M11 takes the -1.5 lens

My glasses have -0.75 correction, but I don't use them with my camera

Yes, according to the SL3 manual my setting is -2.5.  Interesting that your differential is similar to mine, albeit with the camera diopter settings reversed.  I think @elgenper found the answer as to why the two cameras are different.  Thanks for the input.