Leica dioptre

[azuled]

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I don't know enough about optics to contribute to that aspect of the conversation, but I do have a warning about the Leica Diopter on all modern Leica rangefinders.

 

They are not secure, at all.  They WILL loosen overtime and fall off, and you must tighten them each time you pick up the camera.

 

I have lost two because of a temporary failure of this routine.

Edited March 19, 2016 by azuled

[ECohen]

Rick

I think you need to set up a Pay Pal account for all the on line consultations you will be preforming.    

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[Rick]

Rick

I think you need to set up a Pay Pal account for all the on line consultations you will be preforming.    

 

 

Nah, it is just simple optics + a brain attached... the second part is where it gets tricky. 

 

Rick

[Rick]

Neil, your explanation is a good start.  But, you need to attach your Rx to your post and your age and then I can make suggestions.  The optics part is easy.  It is the special circumstance of each individual patient case that is where the variability arises.  You, for example would not make a perfect mono vision candidate as you have tried with the contacts.  You are so right eye dominant the left probably isn't going to be used automatically by your brain if it has a near contact.  But, it might work if you close your right eye when you want to see the dials... not perfect but, you don't have a perfect visual system.

 

Your right eye would need a contact with perfect distance vision.  Then you would put a +0.50 to +1.00 diopter in the Leica.  This would be the set up assuming the right contact works perfectly and the left one isn't too distracting.  It might take many months for your brain to adapt (or none at all), but I'm betting you might not have the patients?

 

Your progressives will work, but you are really only using one eye and therefore the reading area in the progressive is less than what you would have with two eyes.  This is mainly because of the difficulty in getting the progressive measured right in the first place and the trouble using just one eye to try and find the correct area to look out of.  But, in the viewfinder the progressive wouldn't be any more difficult to learn how to use for you as anybody else. 

 

And, remember;  Among the blind the one eyed man is king!  

 

Rick

[pico]

Thank you, Rick, for the explanations. I can understand the math, but not the art. I suspect combinations and conditions are everything. I pay over $600 a pair for tri-focals and nobody gets it right. I brought a Leica with me on my last visit and he dismissed advising by literally pushing it away. Maybe you could write an article on how idiots like me can choose an eye doctor.

[Guest NEIL-D-WILLIAMS]

Neil, your explanation is a good start.  But, you need to attach your Rx to your post and your age and then I can make suggestions.  The optics part is easy.  It is the special circumstance of each individual patient case that is where the variability arises.  You, for example would not make a perfect mono vision candidate as you have tried with the contacts.  You are so right eye dominant the left probably isn't going to be used automatically by your brain if it has a near contact.  But, it might work if you close your right eye when you want to see the dials... not perfect but, you don't have a perfect visual system.

 

Your right eye would need a contact with perfect distance vision.  Then you would put a +0.50 to +1.00 diopter in the Leica.  This would be the set up assuming the right contact works perfectly and the left one isn't too distracting.  It might take many months for your brain to adapt (or none at all), but I'm betting you might not have the patients?

 

Your progressives will work, but you are really only using one eye and therefore the reading area in the progressive is less than what you would have with two eyes.  This is mainly because of the difficulty in getting the progressive measured right in the first place and the trouble using just one eye to try and find the correct area to look out of.  But, in the viewfinder the progressive wouldn't be any more difficult to learn how to use for you as anybody else. 

 

And, remember;  Among the blind the one eyed man is king!  

 

Rick

Rick

My Rx is in KL , I am currently in Cameroon on an Oil Rig............home in 2 weeks time.

 

The part about closing my right eye to make my left eye work would also be a pain in the butt as I cant close my right eye on my own, I would need to pull the lid of my eye down with my finger to close my right eye :(

 

Your right about not having patients............i've got to be the worlds worst

 

I am going to be getting new progressive glasses this time home. I plan to take a borrowed M240 with me to the optician so that she can see what I am trying to achieve ( I was meant to have done it last month but never got around to it) which is great as I will make sure she understands that the long part of the lens for distance is more important than the near part.

 

Thank you so much for taking the time to try and help me, someone else mentioned already what a wonderful bunch of people we have on this forum, and that is so so true

Cheers mate

 

Neil 

[Jeff S]

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Jeff, I would need to know your age and Rx to help explain your particular situation, "by the numbers."

 

Rick

 

Age 65+

 

Prescription 2 years old and needs a tweaking for left eye...I use right eye for shooting....but current specs work well...

         Sph       Cyl     Ax

OD   -2.25   +2.25    5

 

OS   -1.50    +1.50   3

 

I have a separate prescription for specs optimized for a couple of feet....only use them for computer screen and museum exhibits.  Regular specs (above) work perfectly well for distance and for using M.  

 

I don't need specs as much for reading, but have reading glasses if my eyes get tired, or if print is real small.

 

Thanks,

Jeff

Edited March 19, 2016 by Jeff S

[Rick]

Jeff, do these glasses you use have near correction in them?  What kind and what amount?

 

Rick

[Rick]

Thank you, Rick, for the explanations. I can understand the math, but not the art. I suspect combinations and conditions are everything. I pay over $600 a pair for tri-focals and nobody gets it right. I brought a Leica with me on my last visit and he dismissed advising by literally pushing it away. Maybe you could write an article on how idiots like me can choose an eye doctor.

 

Pico - Like all doctors, they have to be good and care.  I do a lot for my patients and don't get paid for all I do.  But, I'm not complaining. I've had marksmen and skeet shooters and flutist and Leica shooters and etc...  They bring in the darnedest things that they want to be able to see.  The nerve of them!    

 

Rick 

[jaapv]

Where do have the 2m from? I have as of now not been able to find the apparent distance of the frames in the RF.

Günther Osterloh, Advanced Photo School.

[ECohen]

Thank you, Rick, for the explanations. I can understand the math, but not the art. I suspect combinations and conditions are everything. I pay over $600 a pair for tri-focals and nobody gets it right. I brought a Leica with me on my last visit and he dismissed advising by literally pushing it away. Maybe you could write an article on how idiots like me can choose an eye doctor.

 

 

I too brought the camera to my appointment and a written exact question, as to be clear of what I needed .......I got the bums rush ....saying he didn't know about cameras...only after pressing him,  he did some calculations and gave me the incorrect number.......very frustrating ..I'd love to find a better doc. 

[pico]

Rick, I have never experienced normal vision, but at Seventy years-old I have adapted. I will close by stating that the Leica M, my long-time friend, is so difficult to use that I'm about to go back to a high-point view Nikon. Tragic, eh?

 

ASIDE AGAIN, AGAIN, AGAIN! The sever for this site is redirecting or tracking replies so that the delay is entirely unacceptable. If it continues, I'm out of here. As if the admin cares. Just stop it!

Edited March 19, 2016 by pico

[jaapv]

No delay here. Are you sure it is not your server?

[Jeff S]

Jeff, do these glasses you use have near correction in them?  What kind and what amount?

 

Rick

 

I've never been asked before....so I'm thinking not?  I only have the Rx as shown....but I do have separate reading glasses.

 

I do have thick Corneas, if that matters.

 

Jeff

Edited March 20, 2016 by Jeff S

[Rick]

Pico, sorry to hear you are moving on to Nikon.  Hope it works for you.  

 

As for you question of where did the 2m frame lines come from.  That has always been confusing.  What's really happening is this.  The whole viewfinder has a -0.50D lens in the system.  Everything you see in the viewfinder adds an additional -0.50D of accommodative demand to your visual system.  Try it.  Look at some figures more than 20ft away with the camera and without.  You will find it harder to see clearly through the viewfinder.  Use your distance correction for both.

 

The diopter cancels out the "overcorrection" Leica has added to the viewfinder.  Some may need a little more due to the way their eyes are corrected with their glasses or how their own eyes are naturally.  A little more than +0.50D will also make the viewfinder clearer inside 2m.  So, it seems some folks here like to little bit extra and are going for +1.0.

 

Also, the viewfinder minifies the image just by the nature of it being a reverse Galleon telescope (I believe?).  The diopter actually gives a little shape magnification, which helps.

 

Something else that is little known is that as we age our own lens isn't providing enough plus power to see at near... so we add reading glasses.  The reading glasses are added to the front of the whole optical ray tracing diagram.  More on this.

 

Your own lens in your eye becomes stronger (more convex) when you focus, but it is behind the Cornea (a powerful lens itself) and in the ray tracing diagram of this system the image projected on the retina is larger than the same amount of focusing done by spectacles.  So, as we age we get a double whammy of focus-pocus problems.  Blur at near and the font we see is smaller on our retina!

 

This explains 30-years of hearing my patients complain that they are using fonts these days that are just too damn small! Even with the correct reading glass power everything is smaller than it was before on your retina.

 

This is the elegance of nature.  When our young eyes focused they made the image clearer and larger.  Now you know why you struggle with reading glasses to read your medication.  

 

Hope this helps,

 

Rick

Edited March 20, 2016 by Rick

[Rick]

I've never been asked before....so I'm thinking not?  I only have the Rx as shown....but I do have separate reading glasses.

 

Jeff

 

Jeff, tip your head up and look through the bottom of your glasses.  Is there reading power down there or not?  I think I already know the answer here and it has to do with your relatively large amount of astigmatism.  But, play along and answer my question.

 

Rick

[Jeff S]

Nope...I didn't understand your question at first....no separate correction or progressive of any kind.

 

Jeff

[Rick]

And, you say you use your distance glasses with the viewfinder and have no problem?

[Jeff S]

Correct.  Are you going to tell me I shouldn't be able to see well?  And you recommend what?

 

Jeff

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[Rick]

No.  I believe the phenomenon you are experiencing is caused by uncorrected astigmatism at axis 90° which makes the horizontal lines that you are converging in the RF to be corrected by about half a diopter.  You already got a diopter in your glasses oriented at that axis.  

 

You probably are able to see up close better than your contemporaries because of this as well?

 

Rick