Prescription glasses, rangefinder, magnifier and focus-precision (APO-Summicron-M 90 ASPH.)

[Strmbrg]

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Sorry if there are existing threads on this topic (there often are, but not always with the "right focus").
Many discussions around focusing-issues can be found, and many are bewildering. This one too, maybe. But maybe not for those with similar sight as mine.

The APO-M-90 was bought this spring. I bought a new one.
I noticed very easy that at infinity-stop, tree-branches and such quite far away (say 100 meters or so) was out of focus. Of course more pronounced wide open.
My first thinking was about some slight mechanical/optical issue in the lens, camera or both.
Then I shot things very far away (maybe 500-1000 meters). Then the infinity-stop-position gave very sharp results.

So, objects at about 100 meters away needed a VERY slight move from infinity-stop. So slight that I cannot see the difference in the rangefinder-patch.
I thought that I just will have to make that slight move out of that knowledge and not based on what I am able to see in the finder.
The 1,4-magnifier combined with good glasses makes me see the slight focus-patch-difference of the very slight move from infinity-stop. Even with my screen-progressives. More of that later.

It is very worth mentioning here that nearly no real photograph focusing on things 100 meters away - taken with a 90mm-lens at f2 - or slightly smaller - is worth making. Just because there are nearly nothing at that distance worth focusing on in a see-worthy photograph, that will benefit from the large apertures depth of field. It may be a "peeper-image" but hardly an aesthetic, see-worthy image. 🙂

I have been thinking of diopter-lenses for a while, but came to the conclusion that they only make sense in a small part of the focusing-range. None of the values will give improvements over the whole range from closest focus-distance to infinity. Not for me at least. I am far-sighted but have some very small issues even at far-distances.

So, why not use the camera with some new progressive-glasses?
I have only been using reading-glasses for many years, because those have been good enough for me before, and the disturbing-level has only occurred after getting in to a range-finder and then pronounced to be an issue worth thinking of a solution to, with the 90mm-lens.
My new thinking about the whole thing came out after starting to use my progressive screen-glasses I already have, together with the camera. Those glasses are "perfect-working" in the range of book-reading to maybe 5 meters. "Full-range-progressives" will therefore work well at any distance with the camera. 

Two issues may occur though (I have not received the new glasses yet):

• I will have to move my head up and down depending on what distance I want to focus at. This issue is already apparent with my screen-glasses and not a problem for me.
• It will be hard to see the 28-mm frame without moving my head around to see them. My 28mm external finder (Fujifilm) does work with glasses on and makes it possible to see the whole frame with fixed position. And, the need to always use the rangefinder-focusing is of course less with the f-2,8 Elmarit.

The Leica magnifier 1,4x is already very much improving the ease of focusing the 90/2,0 wide open.
I cannot use the magnifier without glasses though. My eyesight-condition gets an amplification of the blurriness when using the magnifier without glasses.
Without the magnifier, the blurriness is not at a distracting-level, with it it attached, it is really distracting.
But, the ability of precision-focusing is of course not bettered without it.
The viewing-experience in the finder is more acceptable without it, but the focusing-result is not, to say it in a slightly other way.

• The 90mm-frame is well inside what I can see with the magnifier and glasses combined.
• The 50mm 1,4-lens is easy to focus with just progressive glasses. The magnifier and glasses-combination here makes it hard to see the complete frame without moving. But the magnifier is not needed with this lens, I have found.
• The 28mm-lens does not really need anything else than my naked eye in the cameras viewfinder, and if I want, I use the external finder to see the frames well inside my full view even with glasses on.

So, for those with similar sight as me:

• Chose eyeglasses with full-range-progressiveness. 
• Chose glasses (a frame) that makes it easy to get your eye close enough to the finder.
• Chose glasses with extra scratch-protective treatment (even though the rubber on the finder probably is protective enough).
• Use the magnifier for the 90mm-lens.

 

Edited July 7, 2024 by Strmbrg

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[TomB_tx]

Interesting, and good suggestions in this pixel-peeping age. My first Leica lens was a 90 (fat) TE I bought in 1968 with my M4, so I used it for everything. I've worn glasses full-time since I was 12, so my camera usage has always adapted to glasses, and even as I moved to progressives the glasses never caused me problems or got scratched from cameras. However, my habits and expectations come from 50 years of film-camera use, and haven't changed much with the addition of digital, so my evaluation of sharpness is based on viewing the complete image at normal viewing distance, and on prints from 8x10 to 20x30 inches. I suspect many of my favorite photos would not pass the sharpness test expected by today's digital photographers, but I like them anyway.

I've had my "new eyes" now about 3 years after cataract lens replacements with new "multi-focal" lenses that also correct my bad astigmatism. These lenses don't actually "focus" as distances change, but give three overlapping images focused at far, mid, and near distances. Your brain learns to separate the sharpest image and (almost) ignore the less sharp edges of different distances. It works better than I expected, especially in bright light and higher contrast situations. However, very close distance, especially in dim light or with low contrast details is worse than I used to have even without glasses - so for fine detail work on mechanisms (like camera repair, etc.) now requires reading glasses. Through all this I was pleased to find that M camera RF use is still great, and I appreciate easier seeing the full VF edges. I notice that the RF patch contrast gets higher as it comes into focus, so that helps with my new eyes.

The cameras I have difficulty with now are TLR ground-glass screens without magnification, as I can't get inches-close to the ground glass like I used to unless I carry reading glasses.

So cataract surgery can be a great improvement overall, and for me was fine for Leica M use, but it isn't a cure for all conditions. I'm still glad I had it done.

[davidmknoble]

I use a -3.0 diopter on all my M’s both digital and film.  Ignoring the 90mm for the moment, I much prefer focusing without glasses, so I also use a neck strap on my regular- and sun-glasses to take them off when making a photograph.

I have used the 1.4x on film bodies for the 90 APO summicron and the 90 Elmarit with great results.  Even at f/4.0, depending on how close the subject is, the depth of field can be shallow.  Film, of course, helps with the thickness of the emulsion.  However, I also ordered a Leica MP 0.85 finder when the a-la-carte was more available and it works great for 90mm lenses, as does my M3.

Because film is taken care of, it leaves digital.  This is the one area where I like the EVF accessory.  For the 50 noctilux, the 75 APO, 90 APO and 135 APO, the EVF allows shallow depth of field focusing with much more accuracy.  For what it’s worth, the 135 APO also has a longer infinity setting, but that is true of all longer focal lengths.  I think the formula is something like 100xfocual length, so wider lenses have shorter infinity distances…

I prefer contacts for all these things, yet as my eyes age, they are more dry so I cannot use them anymore!

[MaticB]

I struggle with similar problem, but already with 35 APO! With my progressive glasses on, when focusing subject - let's say 100 meters apart - I have to correct focus point slightly. It get on my nerves slightly, but now I accept the obvious. Anyway, occasionally I helped myself with Visoflex.

[spydrxx]

I've had vision/focusing problems with my Leicas for at least 25 years. When I wore single vision glasses I had to change screw-in diopters every two-three years, and it was quite frustrating, but I knew my lenses were focused at infinity when at the infinity stop, even if the RF images weren't quite in perfect alignment, which I compensated for by adjusting that little horizontal screw - just a touch, and rarely shot wide open so DOF saved my bacon. When I switched to progressive lenses I encountered a new issue - adjusting the eyeglasses nosepieces so that when I watched TV everything was in focus and hoping the same for the rangefinder, After cataract surgery and lens replacement (I chose close focus lenses so I could see my watch and computer screen without glasses) I stayed with progressive eyeglasses for mid and distant (think driving) focus, but still encountered the exact adjustment of them on my face again for TV and RF focusing. Then I started using Barnack bodies, which have a built-in telescope/diopter adjustment....quite a relief, but it introduced a new issue...the camera eyepieces scratched the protective anti-reflection coating of the eyeglasses so I now have to replace them each year...which is probably a good idea anyway, but not inexpensive. I have a plastic eyepiece cover on my M body, I got from DAG, which protects my eyeglasses from scratching, but nothing like that exists for the Barnacks, which are metal. I've tried removing the eyepiece and recoating it with a rubberish compound, but that didn't last. Thought about having plastic non-scratch ones made from a local CNC machine shop, but there are still the brass screws holding them in place which can still scratch my eyeglasses. So, in the end, for film, I love the Barnacks for the magnified and vision corrected focusing, and for digital there is a built in diopter adjustment in my Sony A7rii or live view screen. So I've sort of found a balance which works for me.

[lct]

2 hours ago, TomB_tx said:

So cataract surgery can be a great improvement overall, and for me was fine for Leica M use, but it isn't a cure for all conditions. I'm still glad I had it done.

Same here but focusing should not be critical at medium aperture so if it is the case with the OP's lens, returning the latter could be advisable provided RF accuracy is OK. What is normal is that focusing with the RF can be hit and miss at full aperture given the shallow DoF. The limits of rangefinder accuracy are almost reached with a 90mm lens at f/2 (same as a 75 at f/1.4 more or less), especially if the OP does pixel peeping.

[Strmbrg]

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Yesterday evening I "enjoyed myself" with sitting in the living room and practiced to get really good focus with the APO 90 fully open. Handheld of course and with the auto set to allow the longest shutter-speed of 1/90.
It was really fascinating how accurate I made nearly every shot whith screen-glasses and the 1,4-magnifier. All from closest distance to say 80 meters. No help from artificial or so much daylight either.
The basic thing is to be calm, take it slow and stop focusing when it looks right, i.e. NOT twist back and forth. Just slowly turn the ring and just stop when the split-image disappears.

The today common and overall "hurriness" applied to almost everything in "the modern life" is nearly never necessary. It is just something taking for granted and nearly never questioned. "Save time, do things faster..." Well, then you may save some time, that you can spend to correct what was done too fast, and the resulting bad result. 😄

Why is it necessary at all to get the image recorded fast? The purpose of the image is to look at it often and long. The following post-processing is "allowed" to take some time.
So just why the hurry when recording it?
Of course, if one is into action-images, everything must be done fastly. But I am not at all into that kind of images. Neither sports, children flying all over the place or crazy dogs jumping around. And if I where, there are several better camera-solutions for those speedy shots than the slow, vintage-tech Leica-M.

Summary, maybe:
Contemplation is a somewhat overlooked - or even not at all known - mindset for "modern people".

[Stuart Richardson]

I think the vision is certainly a component of this, but a lot of the issue is the stress that modern lenses and high resolution digital sensors put on the rangefinder focusing method. Focusing a 90mm wide open with a rangefinder designed mostly for 50mm lenses on 1950s film is a tall order. It is a testament to Leica's engineering that they can do it at all. I know it is not fun, but this is the area where the EVF really makes itself useful. I have an M10M and I find that the EVF is very helpful for 75-135mm lenses in particular. If nothing else, it will probably cut back on eyestrain from trying to squint to see the RF as well as possible. With film I would just try to stop down. I bought the 1.25X magnifier back in the day, but I found that it did not really help my focusing. If I recall, the extra magnification was offset by the increased distortion and sensitivity with eye placement. Perhaps the 1.4x works better. On film I was lucky to be able to order my M7 a la carte back in around 2005. I got a version with a .85x finder and that does help with the longer lenses...more so than the magnifier in my experience. 

[jaapv]

One of the issues is that one must be able to see the rangefinder patch AND the background clearly to achieve accurate focus. The patch is at a virtual 2 meters and the viewfinder is a telescope system which needs eye  accommodation from close up to infinity.  If the eye lacks sufficient accommodation ability (or vari-focus lenses),  getting accurate focus at all subject distances will always be a challenge.
In such cases a magnifier may help, but the magnifier may (will) need a diopter itself to have the focus point at a compromise distance, say 3m.  This diopter value is very often different from the optimal diopter value for the "naked" viewfinder.

It is a matter of experimenting, one can use throw-away reading glasses from the chemist to determine the best viewing experience. It is possible to calculate the values from a prescription, but only an M-owning optometrist will be able to do so. 

If you really want to get the best possible solution this site has excellent reviews.

[Strmbrg]

I also have and use the Visoflex 020. But only for real close-up shots with the new close-focus Summilux 50 together with an older ELPRO-variant.
I don't really like the electronic finder-solution. Maybe mostly for "emotional" reasons rather than "technical", I don't really know. But regardless of why, I know that I prefer the pure optical solution. One sure thing though is that the Visoflex consumes battery-power. The M10-R (which is my only Leica) hasn't the most capacity-full batteries.
Another thing is that I like the way the optical viewfinder has similarities to my naked eyes way to look at things. I.e. I use my eye to see things clearly in the finder - regardless of the distance - without the need to use the focus-ring to get them clearly visible. It is very similar to look at things without a camera.
Another aspect is that this rather small camera gets more and more clumsy with EVFs, handgrips, half-cases, finger-loops and thumb-grips. With all these things together one could as well stroll around with an SL or some other machine of that size. Not a very big deal, but at the same time nothing that gets in the positive direction of the cameras "appearance".

Edited July 7, 2024 by Strmbrg

[Jean-Michel]

I wear glasses. In order to clearly see the rangefinder patch and the red symbols in the viewfinder I found that I needed a diopter. I simply went to my optometrist and held their diopters against the eyepiece and found the one that worked best for me. I then purchased that one from my Leica dealer.  Basically, in my case, the minus 5 diopter of the eyepiece and the plus 5 of the purchased diopter add up to a zero diopter. With my SL2, the diopter is also at just about zero.

[dpitt]

On 7/7/2024 at 4:29 PM, jaapv said:

One of the issues is that one must be able to see the rangefinder patch AND the background clearly to achieve accurate focus. The patch is at a virtual 2 meters and the viewfinder is a telescope system which needs eye  accommodation from close up to infinity.  If the eye lacks sufficient accommodation ability (or vari-focus lenses),  getting accurate focus at all subject distances will always be a challenge.
In such cases a magnifier may help, but the magnifier may (will) need a diopter itself to have the focus point at a compromise distance, say 3m.  This diopter value is very often different from the optimal diopter value for the "naked" viewfinder.

It is a matter of experimenting, one can use throw-away reading glasses from the chemist to determine the best viewing experience. It is possible to calculate the values from a prescription, but only an M-owning optometrist will be able to do so. 

If you really want to get the best possible solution this site has excellent reviews.

As Jaap said, it is very important to use glasses that allow perfect sight at 2m distance and probably also at more or less the distance of the actual object. People using reading glasses for the RF will probably find that they do not work because they are optimized for 30cm distance. Screen glasses optimized for 70cm may do better, but not ideal. I have been using reading and screen glasses for a while with both diopter correction and astigmatic correction. Over time I noticed that my oldest (weakest) screen glasses are now ideal for using the RF, so what used to be optimised for 70cm is now ideal for 2-5m and is now very good for RF. Because the correction is small they also work reasonable well at infinity, so I do not have noticed any issues there.

For office work (reading and screen) I now use bifocal glasses but even then they are too strong for the RF and I prefer fixed glasses for the RF anyway.

Using glasses makes the 28mm frames hard to use. No problem for me because I like 35mm better for other reasons too. Those who prefer 28mm could make use of the add on 28mm OVF because it has more space around the frame. And of course the EVF is better if the M model allows it.

Regarding focusing on  distant objects with 90mm and 135mm. The infinity stop is for far away objects. With perfect eyesight one can see focus differences in the RF for objects up to 1 km, so no wonder 100m distance is not sharp at infinity stop and a small aperture with a 90mm lens.

22 hours ago, Jean-Michel said:

I wear glasses. In order to clearly see the rangefinder patch and the red symbols in the viewfinder I found that I needed a diopter. I simply went to my optometrist and held their diopters against the eyepiece and found the one that worked best for me. I then purchased that one from my Leica dealer.  Basically, in my case, the minus 5 diopter of the eyepiece and the plus 5 of the purchased diopter add up to a zero diopter. With my SL2, the diopter is also at just about zero.

Using the diopters of the optometrist to find out what works best is ideal.

[CP93]

N00b question, as I've always just shot with glasses on and moving around to see the edges:

How do you determine what size strength diopter you need?

Edited July 9, 2024 by CP93

[delta100]

If you want a Leica diopter go to your Leica dealer.

[lct]

In theory add 0.5 dpt. to your prescription but better bring your camera to your optometrist or your eye doctor or an optician having the whole range of diopters and try the values in person around your prescription. I just did it after cataract surgery and it worked perfectly.

[spydrxx]

I think you mean what strength rather than size. Your camera only accepts one size, based on the embedded threads. As for how to determine the correct strength, read thru the various threads on this topic...different people have different needs and ways of approaching the issue. Using an optometrist's diopter wheel and having a lens ground to your exact specs is best and probably most expensive.  The question is do you wear glasses or contact lenses, and will you be wearing them when photographing, or will you be taking them off/out to photograph? You can see the issues I faced above. BTW I picked up an inexpensive diopter wheel years ago so I'm always prepared as my eyesight changes...but the non-professional (optometrist/opthalmologist) wheels are usually only in full diopters, not fractional ones, so not perfectly accurate, but in the ballpark.

[delta100]

Hello Ict, your cataract issue is very interesting. I have a cataract problem looming.  I no longer need the use of the Leica view finder diopter,  my focus problem as gone away because of the DOF caused by cataracts 

[lct]

54 minutes ago, delta100 said:

Hello Ict, your cataract issue is very interesting. I have a cataract problem looming.  I no longer need the use of the Leica view finder diopter,  my focus problem as gone away because of the DOF caused by cataracts 

I used a +3 dpt. Leica correction lens before the cataract surgery and -1 dpt. after it.

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[Strmbrg]

I received the Bresson magnifier some days ago.

It is not possible to change diopter-value independent of the magnifying-value. Luckily for me, the greatest magnifying-value did correspond to the right diopter-value. But, if one needs a diopter-value in the other end, there will be only a 1,1x-magnification. 
I have also ordered the Light Lens Lab magnifier, but not received it yet. As far as I can understand, this one has a fixed magnifying-value of 1,4x independent of the diopter-setting.

[MikeW]

My shooting eye has a sphere correction of +0.25 (slight far-sightedness) - that, plus a bit of astigmatism in that eye, is enough these days to lower contrast when focusing my eye on fine detail.

I do not walk around with glasses on, and I would hate to do so, although if I were a regular live-view user, I would have to carry them at least.

A Leica diopter I picked up a couple of months ago, for me, made an appreciable difference.

Improving contrast on the focus patch provides rewards regardless of the distance to the target. On my 28/35/50 Lux, this has been enough; I haven't shot my 90 APO Chron enough since getting the diopter to be certain enough to weigh in, but it's been a decent experience so far