Astigmatism and rangefinders

[mbray]

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I'm somewhat new to this Leica world, but have used Voigtlanders and even Zorkis in the past, then Canon A1, twin-lens reflex and Mamiya 645 until the digital slr took over with its adjustable viewfinder.

I have astigmatism in both eyes, 20 degrees in my dominant left eye and 160 in my right eye. I have always used my left eye on viewfinders and find I do get a double image vertically but it's fine horizontally. Accepting this, and still wearing glasses, I have found that I have had very few focus issues in the first hundred or so pictures. Infinity focussing is no problem. The only time I have had a problem is when trying to focus on a branch of a tree in full leaf - probably I should have zone focussed instead!

[Guest mc_k]

...do you happen to know or can you estimate, what the virtual distance would be with a +-0 dpt.?...

 

that was a lob

[rolu]

that was a lob

 

I'm not a native speaker, but I don't take this as a compliment, wrong?

 

I still don't understand the preset of a -0.5 dpt. in an aging population. The explanation

...

The -0.5 dpt preset of the eyepiece just means the viewfinder controls—i. e. frame lines, rangefinder patch, and LEDS—will appear at a virtual distance of 2 m/6 ft to the normal-sighted (or properly corrected) eye. ...

doesn't make any sense:

The LEDs are clearly readable unless you are blind. I'd rather have them smaller and give me more information (ISO, ...)

Focus accuracy is key!

What do you think?

[Guest mc_k]

sorry Rolu, nothing uncomplimentary was intended.

 

I think his comment about -0.5 just follows by definition of diopter.

[ho_co]

ro--

That's the standard projected distance of all Leica M cameras, I think, and was also for the Leicaflexes, though not for the R series and other SLRs. That distance was chosen by Leica precisely to make it easily usable for your "aging eyes."

 

I think 0 dpt actually translates to 'undefined,' and in this case would mean 'inside they optical system of the eye.'

 

Why do you feel that a 2m projected distance for the rangefinder and frame lines could be improved? You may be right; I certainly don't know; but keep in mind that doing so would likely require a complete redesign of the rangefinder, since this design goes back to the M2.

 

I don't follow what the size of the LED readout has to do with the focal point of the optical system. I think the difficulty of putting additional information into the readout has more to do with the physical availability of space within that end of the rangefinder system. I'm sure you're aware of how tiny the cutouts are in the foils that produce the rangefinder frames, right?

[rolu]

sorry Rolu, nothing uncomplimentary was intended.

...

 

No problem - BTW the German word "Lob" means "praise". (;-))

[Guest mc_k]

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lob can mean a pitch in baseball that is "too easy" for the other player

[ronnysoh2009]

 

Photo above shows my little experiment with a personalised diopter for my astigmatism.

 

I just had a new pair of spectacles done, what with my increased astig over the years.

My astig's now 225 left and 225 right. Along with my new spectacles, I also ordered

a small lens (225 astig) from the same optician shop - a lens that I can fit to my M8.2.

Costs the equivalent of US$30.

 

The smallest diameter they can cut the lens for me was 20mm. They drew a horizontal

line across the lens for me so that I will get the orientation of the lens correctly - it has

to be oriented with the red line aligned horizontally for my particular type of astigmatism.

 

I first tried glue, but due to the organic vapours released as the glue dries, the astig lens

got clouded. So did the E-Clypse Eye Cup that the astig lens was glued to.

 

I then ordered a second piece of astig lens.

 

This time I used double-sided tape to adhere the 20mm diameter lens to the M8.2's

viewfinder (as shown in photo above). Looks tacky; I don't know how to cut a perfectly-

shaped doughnut from double-sided tape.

 

The advantage of this arrangement is I can get my eye very near to the viewfinder.

Framelines are easier to see, compared to when I'm wearing spectacles, which

introduces additional distance between my eye and the viewfinder.

 

The only snags are:

 

(i) the double-sided tape does not do its job well when the camera is placed in the

camera bag. The 20mm diameter lens gets peeled away when jiggled about inside

the bag.

 

(ii) when I need to attach my 1.4X magnifier, I have to peel off the astig lens, then

re-attach it again when I remove the magnifier.

 

If only there was a way for me to mechanically couple the 20mm diameter lens

to a small metal disc that comes with screw threads that allow for attachment

to the M8.2's viewfinder.

[walterleica]

Have a look at walterrxeyepiece.com .After reading this thread and being an astigmatism sufferer myself i designed and manufactured this device where you can insert your own prescription lens and be able to tilt the camera at any angle.

A very big thank you to the leica user forum and threads like these:cool:

[santdtman]

TRy one of these tools:

match Technical Services - E-Clypse EyeCup MAG

 

It should be possible to replace the magnifying lens with Your diopter lens.

Or alternatively ask the company who does the MAG, if its possible to build

in one (your) custom lens instead of the magnifying lens...

[hoppyman]

Not only that Andy but a lens to correct for astigmatism would have to be aligned at the same angle in the eyepiece every time or it could be ineffective or even detrimental.

This is a fundamental problem.

Astigmatism is the double whammy and separate from any needed diopter correction or magnification.

Relearnt recently when I have now found that my shooting eye is worse than my spare and I just missed in about 30% of crititical focus shots. Testing carefully since I've found that my camera and lenses are still spot on but my shooting eye is not just imprecise leading to random error but actually leads to a consistent wrong back focus effect (over about 200 frames on two days). In my case specifically around 50mm rearward error in portraiture conditions.

 

 

When I spoke with my normal optician, they told me that they couldn't make a properly corrected lens small enough to fit the correction ring......

[Jeff S]

Geoff, Andy posted his comment three and a half years ago. I love how some of these dormant threads re-engage once someone adds a comment.

 

So, now that it's happened again, let me add that because of my astigmatism, I always use eyeglasses and have my prescription regularly updated to ensure my vision is corrected before I look in the VF. Otherwise magnifications and such will only emphasize the errors. I need glasses for distance vision, and sunglasses for outdoors, anyway, so I might as well keep them on whenever shooting.

 

Jeff

[jlbeek]

Not only that Andy but a lens to correct for astigmatism would have to be aligned at the same angle in the eyepiece every time or it could be ineffective or even detrimental.

This is a fundamental problem.

Astigmatism is the double whammy and separate from any needed diopter correction or magnification.

Relearnt recently when I have now found that my shooting eye is worse than my spare and I just missed in about 30% of crititical focus shots. Testing carefully since I've found that my camera and lenses are still spot on but my shooting eye is not just imprecise leading to random error but actually leads to a consistent wrong back focus effect (over about 200 frames on two days). In my case specifically around 50mm rearward error in portraiture conditions.

 

Hi,

 

Regarding the above comment.

 

The Walter RX Eyepiece ® | "Capture the decisive moment with a Walter RX Eyepiece”Walter RX Eyepiece ® | "Capture the decisive moment with a Walter RX Eyepiece” will solve all your problems with one eyepiece.

 

Have a look.

[Double Negative]

We'll be doing a full review of the Walter RX Eyepiece over on La Vida Leica very soon; we have one enroute! Will let everyone know when it's up.