Why is the viewfinder @ -0.5 diopters?

[jimleicam3]

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I just returned from the eye doctor with my M8. I was having problems with getting dead on focus ( I wear glasses, very nearsighted), so after a number of tries, I could focus best with the addition of +0.5, which brings the viewfinder to 0.0 diopters. If you had 20:20 vision, why would you need to have the viewfinder make any alterations? If I can see 20:20 with my glasses, why should I have to go out and buy for around $80, to get my viewfinder to work with my glasses? What am I missing? Thanks

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[jaapv]

because it is calibrated at 2 meters, not infinity

[jimleicam3]

At the eye doctor I was about 8 feet away from the eye chart, without my camera I could read the letters just fine, with the M8 I could not read as many letters, until the +0.5 lens was added. so I guess I still don't have a clue. Thanks for your help/advice

[jaapv]

There is a quite technical explanation. I'll see if I can find it tonight. In the meantime, the Megaperls 1.15x magnifier with diopter adjustment solves this problem perfectly.

[jimleicam3]

Thanks for your help, where might I find one of those magnifiers? Thanks

[Shootist]

With NORMAL YOUNGER eyes the -.5 diopter has no effect, your normal younger eyes can adjust to it without any problems. When "WE" get older our older eye can not make the slight adjustments as easy or at all.

 

Why does Leica set the viewfinder at a -.5 diopter. I have no idea but it has been like that for decades. It must have something to do with how the viewfinder/rangefinder works.

If you had 20:20 vision and your eyes could still focus on close up objects, didn't need reading glasses, you wouldn't need any add-on diopter.

 

I'll bet that without your glass, which are for distance (Right), you could see the eye chart OK with or without the camera in-front of your eye.

[t024484]

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I had exactly the same problem. My eye is 0.0 so I needed a +0.5 diopter.

Since I found the image still relatively small, I bougt Leica'magnifier. For the price of these two adapters, +/- 300, -Euro, you can buy a decent point and shoot camera.

Anyhow, I had problems all the time that those damned things loosened themselves and fell off.

 

Finally I lost them forever and bought a megaperls 1.15 magnifier plus a built in diopter from -3 to +1. Delivery from Japan was within days, for roughly 100,- Euro.

It doesn't come loose and performs impecable.

 

Megaperls Webshop - Films and more directly from Japan

[lars_bergquist]

Both SLR and rangefinder cameras have finders with the image (and sundry other fripperies, like meter readouts, bright frames and rangefinder patches) at an apparent distance of one meter (e.g. Nikon and others = 1 diopter) or the more convenient 2 meters (Olympus OM SLR, Leica M = .5 diopter). The reason is, I think, that an 'infinity finder' would be too bulky. Remember, the actual distance from the eyepiece to the screen or the frames mask is measured not in meters, but in millimeters!

 

I am 72 and my eyes are forever focused past the horizon. Therefore I use spectacles with progressive lenses. With frames and lenses that allow me to put my sighting eye reasonably close to the eyepiece, I can see all viewfinder info in the M8, and the 35mm frame and (partially) the 28mm frame of the M4-P. And sharply! A little bit of experimentation will soon teach you through what part of the specs lenses you see an object at a distance of 2 meters (and thus the frames etc.) sharply, and then you will instinctively use that head and camera position. This is just as fast as without specs, and I can use my left eye to observe the scenery ... and there's nothing to screw in or off or to fall off, and if I have to check manual shutter speeds or f-stops, well, I can do this immediately without changing or putting on specs. Believe me, this is the recipe for action photography. Get your progressives now and forget your problems.

 

The old man from the Age of Brilliant Finders

[Shootist]

I had exactly the same problem. My eye is 0.0 so I needed a +0.5 diopter.

Since I found the image still relatively small, I bougt Leica'magnifier. For the price of these two adapters, +/- 300, -Euro, you can buy a decent point and shoot camera.

Anyhow, I had problems all the time that those damned things loosened themselves and fell off.

 

Finally I lost them forever and bought a megaperls 1.15 magnifier plus a built in diopter from -3 to +1. Delivery from Japan was within days, for roughly 100,- Euro.

It doesn't come loose and performs impecable.

 

Megaperls Webshop - Films and more directly from Japan

 

 

I use a +1 diopter all the time and I have the Leica 1.25 mag and use a +1.5 diopter on that when I use it, not often. I have never lost either diopter and I have never had the magnifier unscrew. Even if the mag became unscrewed I have the supply chain hooked to the strap lug on the camera body. Don't see how you could lose the magnifier if you used it as intended.

[Terry Kelly]

. . .and bought a megaperls 1.15 magnifier plus a built in diopter from -3 to +1. Delivery from Japan was within days, for roughly 100,- Euro.

It doesn't come loose and performs impecable.

 

Megaperls Webshop - Films and more directly from Japan

 

Couldn't agree more, the Megaperls magnifier is excellent, never comes loose and the internal focus ring doesn't need continuous adjustment, once set it stays set.

[lct]

...Get your progressives now and forget your problems...

Could well stop proscrastinating then... Thanks for the info.

[gravastar]

I use a +1 diopter all the time and I have the Leica 1.25 mag and use a +1.5 diopter on that when I use it, not often. I have never lost either diopter and I have never had the magnifier unscrew. Even if the mag became unscrewed I have the supply chain hooked to the strap lug on the camera body. Don't see how you could lose the magnifier if you used it as intended.

Unfortunately the Leica magnifier can unscrew into two separate sections and when it does it's all too easy to loose the small pin that the lanyard attaches to. That's what's happened to mine.

 

I keep intending to ask Leica for a replacement pin.

 

 

Bob.

[thompsonkirk]

The Megaperls site says the magnifier isn't available for use on Leica cameras in US or Germany.

 

Can one order it anyway (presumably for a telescope, hunting rifle, or something else)?

 

Seems to cost $155 US.

 

Kirk

[ho_co]

Kirk--

Leica has the exclusive rights to supply a finder magnifier in Germany and in the US for rangefinder cameras only.

 

All you need to do is tell the supplier that you're going to be using it on a reflex and you're home free.

[jaapv]

I could not find the reason for -0.5 diopter in literature, but I suspect the simplest explanation is the most likely one: Across the spectrum of human eye aberrations, a distance of about 2 meters is the one the highest number of users can focus on effortlessly, so that makes it the most universal choice for the virtual distance of viewfinder elements.

[ho_co]

Jaap's explanation is reasonable.

 

In the Leicaflex, the SL and the SL2, Leica also used a 2 m apparent distance while other SLR manufacturers were using approximately 1 m. The explanation at the time was that Leica users tended to be older and therefore tended to be able to focus more easily on the greater distance. (With the Minolta-based R3, Leica SLRs went to the 'standard' 1 m apparent distance.)

 

Caveats about generalizing from the above:

 

1) Most modern higher-priced cameras include a diopter adjustment, so the question is moot.

 

2) The M camera has had the same -0.5 diopter since its inception, at which time I doubt that a comparison of other brands' users' ages would have served much purpose.

 

3) Didn't screw-mount cameras before the IIIg have variable diopter settings on the rangefinder? Perhaps Leica generalized from observed usage.

[Shootist]

3) Didn't screw-mount cameras before the IIIg have variable diopter settings on the rangefinder? Perhaps Leica generalized from observed usage.

 

Yes a person I work with has a IIg??? and it has a diopter adjustment lever near/under the rewind knob, IIRC.

I could never figure out why Leica omitted that on the M series. Could be the new rangefinder, and size of the camera, didn't allow for it internally.

[lars_bergquist]

Again, the rangefinder adjustment had nothing to do with the user's eyesight problems, if any. If this had been the case, adjustment would have been needed for both the rangefinder and for the separate finder eyepiece. After all, the same deficient eye was used to look through both.

 

And such diopter adjustment WAS indeed offered, as of 1933—by way of paired, identical dioptric correction lenses for the two eyepices, sold as a pair (code ORTUX)! Which neatly disposes of the superstition about the 'rangefinder dioptric correction', copied from book to book and from edition to edition by thoughtless writers (who obviously never considered actually using the cameras they wrote about).

 

The truth is the following. The Leica II, of 1932, had a unit magnification rangefinder. So the effective rangefinder base was the distance between the centers of the two rangefinder windows, no more, no less. This was later deemed insufficient for the 13.5cm lenses however. So with the advent of the III, and later the IIIa, the magnification was increased to 1.5x, thus increasing the effective base by the same factor.—All well and good, but now the rangefinder was a little telescope, which had to be focused for near and far subjects. PLEASE OBSERVE that the adjustment lever around the rangefinder eyepiece (around the rewinding knob from the IIIb) was marked, not with dioptries this or that, but with an infinity mark! So, if you were e.g. nearsighted, you would have screwed negative corrrection lenses into both eyepieces of your shiny new IIIa, AND then focused your rangefinder separately.

 

Now proper engineering procedure would have been to redesign the rangefinder with a longer physical base. Barnack did not do that. He used instead a patchwork approach which in fact created a new problem with the solution of the first one. The prototype called the 'Leica IV' would have solved these problems with a radically new design approach, a combined rangefinder in the spirit of the Contax II (and the later M).

 

But Barnack contracted pneumonia and died in 1936, and the IV was dropped. With the IIIc in 1940, manufacture was radically simplified; the camera was in fact totally redesigned. But Barnack's death had thrown Leitz into a coma. While manufacture was much improved, the ergonomics of the camera was left as it was, warts, quirks and aggravation and all, by a company that did not dare consider a departure from what was now a sanctified design. It took a world war to get Leitz out of the rut. And then of course the result was the M3. But—even after that, the old formula was trotted out again with the IIIg, separate rangefinder, separate dials for slow speeds and fast (rotating, needless to say!) with a minimum of concessions to user friendliness. Leitz did really never believe in new things, even though Ludwig Leitz was deeply involved in the design of the M3. The old guard was against it.

 

So this is what the lever is for.

 

The old man from the Age of the IIIf

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Hallo,

Look here: Leica M

[ho_co]

Bravo, Lars!

 

Another bit of the history of the marque aptly filled in!

 

Thanks.

[drtomm]

When you look through the Leica viewfinder, you are looking at a virtual image (not the real thing) at a distance of 0.75m, hence the -0.5 diopters. When considering a corrective lens, deduct the -0.5 D from your eyeglasses correction.