Diopter correction advice

[frank-grumman]

Hey folks, I just picked up a perfect Nikon FM3a here. Would that my near distance vision were so good. I need + 3 diopter correction. Leica, if it fits, is 109$, Nikon, which does fit, bout 20$. Any advice you all might have I'd appreciate.

 

[rhl-oregon]

Stick to Nikon optics for Nikon SLRs. I use Nikon -3 on my Fuji GF670 and GA645. I don't think Leica screws are compatible, and the price is comparatively wrong! good luck.

 

[Shac]

If you mean a Leica M Diopter they are too small a diameter to fit the Nikon eyepiece (I just checked) and Leica R diopters (R4-R7) are square and unthreaded. As Robert says - stick to Nikon

 

[peterm1]

Not sure of the Leica one fits Nikon in any event. But as you say the Nikon ones are much cheaper to buy and more readily available. (I recently looked on eBay and the price difference was stark. I dont imagine there would be much if any difference in quality.)

Now here is something you must be aware of. Both Nikon and Leica camera viewfinders come standard with a non-neutral diopter. ie the viewfinder glass is not optically flat but rather has an inbuilt correction. I think in both cases it is -1 or thereabouts so you need to make allowances for this if you are trying to calculate which diopter you need from a theoretical perspective. Also this will not be the same as your reading glasses if you use them. The apparent distance of a Leica finder is about 2 meters. The distance assumed for reading glasses is much closer. So be careful that you really know which diopter correction you need.

If you know for certain that the diopter you need is +3 thats fine but if you are basing this on an assumption about your eye glasses, be careful.

I have found that the best way of checking which diopter to use is by trial and error. I go to a pharmacist where they sell cheap non-prescription reading glasses taking my camera with me. Then, using their reading glasses with various diopters I peer through the viewfinder to see which one gives the sharpest result. Eventually this allows me to find the diopter that works best. Thats the viewfinder adjustment lens I buy. As these reading glasses come in half diopter increments and so do the viewfinder diopter adjustment lens it will work reasonably OK (although bear in mind sometimes what you need can be a quarter diopter and neither Nikon no leica provides these). Alternatively if you are friends with your optometrist take your camera to him / her. They usually have little eye test lenses with different diopters and if you ask nicely they may allow you to hold up various of these as you peer through your finder. Again this allows you to know exactly which diopter works in practice with your camera.

If you still have questions try Googling. I know from when I was buying a diopter adjustment lens a couple of years back and researched it that there are lots and lots of threads on this on the internet.

The following will not work for you but may help others. The following store (see link) also sells a very nice magnifier / diopter adjutment lens that is infinitely adjustable between I think -3 and +1.5 its not cheap but it works well and if your eyes change over time (mine did) you do not need to buy a new lens - you just change the setting by rotating the adjustment ring. The lens in this link is for a Leica - anuyone interested needs to check to see if they make one for the Nikon, I cant recall. It also comes in various magnifications but most people find it most useful for its variable diopter adjustment.

http://www.japanexposures.com/shop/accessories/ms-mag-x1.35-magnifier-for-leica-m.html

 

[awilder]

Nikon is best way to go. All their correction lenses are labeled indicating the total system power of the viewfinder power (-1 D) with the power of the diopter lens. For example, a +3.0 actually measures +4.0 but combined with the finder's -1, it becomes +3.0. Pick the number that matches your spectacle Rx for distance. If your spectacle distance correction is +3.00 (in your shooting eye), get the +3.0 correction lens. If you don't know the spectacle Rx, ask your eye doctor or optician that made the glasses.

 

[brusby]

I found the variable type diopter the most useful because, as someone who is a bit farsighted, one setting is not correct for all focusing distances. If I'm focusing near infinity I need one setting on the diopter, and if I'm focusing on something very close I need to readjust the diopter quite a bit for things to be sharp. For that reason, my Leica fixed diopter has been sitting unused in the drawer ever since I bought it.

So, while the advice above about checking at your local optometrist seems sound, you might want to include both distant and near focusing tests on your checklist.

 

[john_s]

The OP needs +3 or thereabouts, so the japanexposures variable unit will not get to that degree of + correction. I agree with the above comments about trial and error, if possible. Try +3 and the adjacent values in poor light (where your eyes have less depth of field). For -ve corrections, I find less is better than more if the values are widely spaced (1 diopter increments) and I need an in-between (I'm -1.5), but for far sight I'm not sure.

 

[Rob-F]

Nikon is best way to go. All their correction lenses are labeled indicating the total system power of the viewfinder power (-1 D) with the power of the diopter lens. For example, a +3.0 actually measures +4.0 but combined with the finder's -1, it becomes +3.0. Pick the number that matches your spectacle Rx for distance. If your spectacle distance correction is +3.00 (in your shooting eye), get the +3.0 correction lens. If you don't know the spectacle Rx, ask your eye doctor or optician that made the glasses.

This is what I have always understood, that Nikon marks their diopter lenses, not with their actual power, but the resulting power together with the prism. That way, you can just pick the lens with the number that matches your prescription.

However, that is not what Nikon is now saying online:

https://www.nikonimgsupport.com/eu/BV_article?articleNo=000004869&configured=1&lang=en_GB

Has anyone else noticed this apparent discrepancy?

 

[Luke_Miller]

I read the link to say that the diopters are still marked with the total correction. That is why Nikon makes a "0" correction diopter (actually a +1).

 

[john_s]

This is what I have always understood, that Nikon marks their diopter lenses, not with their actual power, but the resulting power together with the prism. That way, you can just pick the lens with the number that matches your prescription.

However, that is not what Nikon is now saying online:

https://www.nikonimgsupport.com/eu/BV_article?articleNo=000004869&configured=1&lang=en_GB

Has anyone else noticed this apparent discrepancy?

I just read the nikon article and it does coincide with my experience with nikon cameras, i.e. my prescription at the time was -1 and I used a nikon -2 diopter. The description might be a bit confusing, i.e. the item labelled -2 is a -1 piece of glass.

 

[peterm1]

I found the variable type diopter the most useful because, as someone who is a bit farsighted, one setting is not correct for all focusing distances. If I'm focusing near infinity I need one setting on the diopter, and if I'm focusing on something very close I need to readjust the diopter quite a bit for things to be sharp. For that reason, my Leica fixed diopter has been sitting unused in the drawer ever since I bought it.

So, while the advice above about checking at your local optometrist seems sound, you might want to include both distant and near focusing tests on your checklist.

I can see that (no pun intended) but we should bear in mind that this may be regarded as a further advantage (if one wants to count it as such) of a rangefinder camera. With an SLR the focus may well change with distance to the subject (not sure how the optics of this works in relation to the internal optics of the camera vis a vis the human eye ) but with a rangefinder camera the view at all subject distances is the same virtual distance from the viewer when viewed through the finder even though the subject may be at a different physical distance. Whatever happens with an SLR this is not a problem for a rangefinder camera. My comment is, I suppose, off topic in relation to this thread admittedly but its worth bearing in mind. I also use a variable diopter with my Leica - not because of any consideration relating to differing subject distances but because (A) I felt it would be easier to get an exact match to my eye - my best estimate of the required diopter was one that fell between commercially available diopters, (b) in any event I knew my eyes would degrade over time requiring further changes to be made. And finally (c) suitable diopters were not available in Australia so I did not want to enter into a trial and error game buying and potentially returning diopter lenses to overseas sellers till I found something that worked for me.

 

[Rob-F]

I read the link to say that the diopters are still marked with the total correction. That is why Nikon makes a "0" correction diopter (actually a +1).

Well, let's look at the chart Nikon is now providing:

Prescription Nikon Correction Lens
+4 +3
+3 +2
+2 +1
+1 0
0 -1
-1 -2
-2 -3
-3 -4
-4 -5


In each case, They are recommending a lens one diopter more negative than the prescription.

My own experience doesn't help much help to clear things up. My Optometrist recommended a minus three diopter. She based this as follows: Spherical = -2.75. Cylinder = -0.5. Best spherical approximation: -2.75 + 1/2 of -0.5, = -3.00. I find I can use either a -3.00 or a -4.00 with satisfactory results. In fact, it's hard to see the difference (slight preference for the -3).

OK, experimentation is valid, and those are my empirical results. Still, three ought to be a clear answer as to whether to include the camera's -1 diopter power, or not to!

Edit: I can't get the 2nd column to line up under "Nikon correction lens" but that is where it is supposed to be.

 

[Rob-F]

I just read the nikon article and it does coincide with my experience with nikon cameras, i.e. my prescription at the time was -1 and I used a nikon -2 diopter. The description might be a bit confusing, i.e. the item labelled -2 is a -1 piece of glass.

Well, if the -2 is really a -1 piece of glass, then that, added to the camera's power, would equal minus 2, which agrees with how the lens was marked. Which would indicate that the added correction should be independent of the camera finder's minus 1 diopter power (which is there to focus a normal eye to one meter*). It really added only minus one diopter, which agrees with your prescription. But I thought Nikon labeled the lens to match our eyeglass prescription. Apparently not! So maybe that was just misinformation.

* The diopter is the reciprocal of the focal length in meters. So 1 diopter/1 = 1 meter, the virtual distance of the Nikon finder image from the eye.

 

[shimokita]

Compatibility among Nikon Screw in diopters...

I was looking for a -2 diopter for a Nikon F3P/F3HP... and was told by the staff at the retail shop that for the F3 High Point Finder you can also use a diopter from the F801, F100, and/or F90. Since an 'original' F3 High Point diopter was hard to find, I picked up an F-801.N8008 eyepiece correction lens and it worked properly... plus it was available in the original box on the shelf at Yodobashi in Tokyo.

Just saying that there might be compatibility options for your specific camera.

Please note the fourth bullet point in the PDF linked below

http://www.nikonusa.com/fileuploads/pdfs/EP_CompChart.pdf

 

[retinax]

I can see that (no pun intended) but we should bear in mind that this may be regarded as a further advantage (if one wants to count it as such) of a rangefinder camera. With an SLR the focus may well change with distance to the subject (not sure how the optics of this works in relation to the internal optics of the camera vis a vis the human eye ) but with a rangefinder camera the view at all subject distances is the same virtual distance from the viewer when viewed through the finder even though the subject may be at a different physical distance. Whatever happens with an SLR this is not a problem for a rangefinder camera. My comment is, I suppose, off topic in relation to this thread admittedly but its worth bearing in mind. I also use a variable diopter with my Leica - not because of any consideration relating to differing subject distances but because (A) I felt it would be easier to get an exact match to my eye - my best estimate of the required diopter was one that fell between commercially available diopters, (b) in any event I knew my eyes would degrade over time requiring further changes to be made. And finally (c) suitable diopters were not available in Australia so I did not want to enter into a trial and error game buying and potentially returning diopter lenses to overseas sellers till I found something that worked for me.

My experience regarding SLRs vs rangefinders is the opposite of yours, and that's also what makes theoretical sense to me.

 

[retinax]

I just read the nikon article and it does coincide with my experience with nikon cameras, i.e. my prescription at the time was -1 and I used a nikon -2 diopter. The description might be a bit confusing, i.e. the item labelled -2 is a -1 piece of glass.

That actually contradicts the description. The explanation why it worked for you is probably that your eyes can accommodate, you don't need reading glasses, do you? That just puts the focusing screen closer to you rather than at infinity.

 

[john_s]

That actually contradicts the description. The explanation why it worked for you is probably that your eyes can accommodate, you don't need reading glasses, do you? That just puts the focusing screen closer to you rather than at infinity.

I think that the Nikon description referred to in a previous post is confusing. Actually, I have almost no accommodation (I'm a bit short sighted and quite old). I still understand that the Nikon diopter marked -2 is a -1 piece of glass.


This is one of the two reasons why I agree that checking by trial and error when choosing a value is best.

 

[shimokita]

I think that the Nikon description referred to in a previous post is confusing.

Yes and no...

If you are referring to Post #8
"Camera viewfinder diopter adjustment"
that link refers to the "Prescription vs. Nikon Correction Lens"

My prescription is cylinder -0.5 and sphere -1.75
since diopter = 1/2 x (cylinder + sphere) <---- edit: this is not correct (see following post)
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

If you are referring to Post #14
that's a description of the actual physical lens correction
Nothing to do with the individual glasses prescribed...

I don't see that the two links are in contradiction ; )
_______________

My Leica MP is different in that the correction diopter does not
provide a "total", rather it's marked as per the added glass

With my Nikon F3P I use a -2 Diopter (as marked)
With my Leica MP I use a -1.5 Diopter (as marked plus in-camera adjustment)
Both to the same effect.
_______________

As mentioned, better to try in each individual situation...

 

[Rob-F]

My prescription is cylinder -0.5 and sphere -1.75
since 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

I would agree that -0.5 cylinder and -1.75 spherical calls for a -2 correction, though I arrived at the number rather differently:

(1/2 x cylinder) + spherical;

(1/2 x -0.5) + (-1.75) = -0.25 + (-1.75) = -2diopters.

It makes intuitive sense, because the cylindrical component occurs at an angle, it shouldn't be added full strength. Adding only 1/2 the cylinder, as an average, rather than the full amount, is apparently the best we can do;
or perhaps the very best we can do, as you stated, is to try more than one lens to see what fits the individual situation.

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

 

[Rob-F]

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.