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Leica dioptre


Guest NEIL-D-WILLIAMS

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No, you don't, because the built in -0.5D makes the apparent distance what it is. You either need the apparent distance or the lens that's between you and the frames. One derives from the other. Even better, you could try and understand the optics involved, for which I'm too lazy.

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Guest NEIL-D-WILLIAMS

I cannot shoot properly without one.

Although I have -4d on my right eye, the -3 will do the job.

Need to get a second one as I have more M's!

John

John

Where do you get the -3 number from. Is it from your prescription or from something else??

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Guest NEIL-D-WILLIAMS

Okay so I'm a roughneck and I think I am getting the jif of all this (I think)

First of all I need to ask my optician what is the power of my glasses that I use for reading..........lets say +2

I then need to ask my optician what is the power of my glasses for distance ......lets say +0.5

Now I should be able to go out and get a Diopter of +1.5 and Bobs your Uncle I should be able to see the focus patch clearly with out my glasses on.

If I decide to shoot with my glasses on then I need to get a diopter of +0.5

Am I heading down the correct path or am I clear as mud ??

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Guest NEIL-D-WILLIAMS

Just read this....interesting

Now, if you want to use your reading glasses, you need to know the diopter of your distance glasses, since you're doing a distant view through the camera. Lets say your distance glasses are +1.50. Then you sum up the diopters, +3.00 in the reading glasses, -0.50 in the camera, and pick a -1.00 correction lens, getting a sum of the desired +1.50.
You REALLY want to buy this correction lens someplace you can exchange it.
However, this is a very contrary way to use diopter lenses on a camera! One normally picks the lens that lets you take off your glasses, so that you can get your eye close enough to the viewfinder to see the corners. But I can understand the motivation, strong presbyopia can mean you can't read the dials and exposure counter on the camera. So you want your reading glasses on to do that.

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Guest NEIL-D-WILLIAMS

Are any of these explanations consistent with any others? 

Does anyone disagree with this method:

Ask your iDoctor what lens you need to comfortably view an image at 2 meters.

Buy a Leica diopter of this value.

Dont shoot with your glasses on.

The problem for most with shooting without your glasses on......... you cant see the rest of the camera dials, cant chimp (not a bad thing) and its a pain in the you know where to have to put on take off put on your glasses all day long :( :( :(

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 I took up this very subject  with the forum when I first got my M.

 
I also took this up with my eye doc bringing him the camera and explaining exactly what I needed to know . He did some calculations talked a little BS the gave me a number that didn't work. Having my glass made the same week I asked the same question to them. Her number was different  and correct.....although I think it was luck.....When I say correct I mean I could work with it. This subject if not as cut and dry to the average photographer trusting  an eye doc that doesn't care about photography.......my question really threw off my doc, I could tell he didn't want to be bothered.
 
I think with all this confusion,the only way to get an accurate number is to go into the Leica store and try them. Also being past 60 my eyes are different in the morning than in the evening. The problem with having the wrong  # is your eyes get tired quicker....at least for me.
 
I currently have a system that works, I  know its not the perfect #. I use a dioptor on the camera and focus through my glasses and most of the time I hit the correct spot (on my progressive glasses). Without my glasses I cant seem to find the correct #.
 
See attached: So what dioptor do I need without glasses?  If I choose to shoot through my glasses what would the best # be?

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Edited by ECohen
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Are any of these explanations consistent with any others? 

Does anyone disagree with this method:

Ask your iDoctor what lens you need to comfortably view an image at 2 meters.

Buy a Leica diopter of this value.

Dont shoot with your glasses on.

 

 

Correct.  So, if you need mo distance correction, then you would need a +0.50D lens.

 

But, very often glasses are slightly over-corrected for myopia and this would cause the need for a slightly stronger diopter, say a +1.00.  This is why the suggestion by japan to go to the optician and ask to try a couple lenses around these powers while you look through the viewfinder at near and far.  It should become very clear (get it) which is best.

 

I'll give another example below.

 

Rick

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I have astigmatism.  I'm sensitive to outdoor light. I don't like contacts....or taking my glasses on and off.  So, I shoot with glasses on (prescription sunglasses in daylight), no diopter needed.  I'm fortunate that my prescription allows me to both see at a distance as well as for focusing and framing.

 

Everyone is different....not just by the numbers, but in terms of viewing preferences and comfort.

 

Jeff

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Cohen-

 

 

The correct diopter with glasses is as follows:  Assume that when you are wearing your glasses you need no correction for distance.  Put another way, if you wore contacts for distance and went into the doctor wearing your contacts the doctor would prescribe zero for distance while you are wearing your contacts.  So... add 0.00 + 0.50 = +0.50

 

The correct diopter with no glasses is as follows:  First we need to correct for your distance.  For your right eye  You need +2.75 of spherical correction in your glasses and in addition +0.50 at axis 136°.  We handle cylinder by halving the cylinder power and adding it to the spherical power to get a "spherical equivalent."  In your case the spherical equivalent is; +2.75 + (+0.50/2)= +3.00

 

So... add +3.00 + +0.50 = +3.50 for the correct diopter.  Remember, it could be off by half a diopter so you may need one as strong as +4.00.  Same goes for my calculation with glasses.  You may need a stronger diopter by half a diopter which would give +1.00.

 

Hope this helps,

 

Rick B)

 

 

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Next, contacts and varifocal lenses:

 

A lot of folks like to wear contacts, I do.  It allows me to see all of the frame and has a multitude of other advantages as well.  With contacts on, I am able to focus much more easily with a simple +0.50 diopter.  For me, it makes a huge difference in the clarity of the finder image.  I don't need to add any additional power as I am not over-corrected in my contact power.  My contact is correct for distance, the doctor did a good job getting perfect.   :p

 

Varifocal lenses are what I remember Lars swore by.  In a varifocal lens you choose the correct power for near by looking down the lens.  In other words, you can find the extra "diopter" you need by simply using a lower portion of your lens.  I've never tried this but, I'm sure it has some limitation but, I bet it works fine especially if you have already habituated to a progressive lens.

 

Hope this helps,

 

Rick B)  

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Lastly, the power that is in your glasses for near has very little to do with anything.  There is no correct power for reading glasses.  This wear the art of prescribing comes in.  

 

Near add power as we write it, is the number in diopters that is "added" to the distance Rx to bring the focal point of the distance glasses power (which should be set to infinity if you want to see clearly at distance!) to some near distance that your patient is comfortable viewing what ever it is they want to see.  A computer on the other side of their desk would need +1.00.  I book held at 40cm would be +2.50.  But, the computer glasses would not be strong enough for reading and conversely the reading glasses wouldn't work for the computer unless your patient is comfortable leaning over their desk and getting their nose 40cm from the screen.

 

So, the near power in your glasses is chosen by, your age, your occupation, your visual demand, the distance you want to work at,the state of the health of your eyes (macular degeneration might want stronger and therefore closer) etc...

 

This is why folks like progressive lenses.  A progressive lens of value +2.50 would have all powers in the lens up to (down to) 40cm.  By moving the head up and down presbyopes can regain their dynamic ability to focus at all distances from ∞ to 40cm.  And, that would include the +0.50 diopter so many need for the viewfinder.

 

Hope this helps,

 

Rick B)

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I have astigmatism.  I'm sensitive to outdoor light. I don't like contacts....or taking my glasses on and off.  So, I shoot with glasses on (prescription sunglasses in daylight), no diopter needed.  I'm fortunate that my prescription allows me to both see at a distance as well as for focusing and framing.

 

Everyone is different....not just by the numbers, but in terms of viewing preferences and comfort.

 

Jeff

 

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

 

Rick

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Cohen-

 

 

The correct diopter with glasses is as follows:  Assume that when you are wearing your glasses you need no correction for distance.  Put another way, if you wore contacts for distance and went into the doctor wearing your contacts the doctor would prescribe zero for distance while you are wearing your contacts.  So... add 0.00 + 0.50 = +0.50

 

The correct diopter with no glasses is as follows:  First we need to correct for your distance.  For your right eye  You need +2.75 of spherical correction in your glasses and in addition +0.50 at axis 136°.  We handle cylinder by halving the cylinder power and adding it to the spherical power to get a "spherical equivalent."  In your case the spherical equivalent is; +2.75 + (+0.50/2)= +3.00

 

So... add +3.00 + +0.50 = +3.50 for the correct diopter.  Remember, it could be off by half a diopter so you may need one as strong as +4.00.  Same goes for my calculation with glasses.  You may need a stronger diopter by half a diopter which would give +1.00.

 

Hope this helps,

 

Rick B)

 

 

Lets here it for the Eye Doc!.......Yep that make perfect sense....I'm using a +1 with  glasses and that works for me.

 

I have a +3 and that does't do it ...... I was offered  a +4 by Peter K, I'll have to contact him and see if he still has it available .

 

I love this forum lots of varied folks willing to lend a hand.......Thanks Rick!!

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Guest NEIL-D-WILLIAMS

Rick

In the ever quest for trying to fix my eyes for Rangefinder photography (Apart from Leica checking calibration) here is my Dilemma.

I was shot in my left eye when I was nine years old with a stone from a catapult that shattered my lens resulting in a cataract. ~30 years later I had the cataract removed in Bangkok and they gave me a replacement lens. This replacement lens was far from perfect but it was 100% better than what I had before the operation..........I could actually see out of my left eye to about 70% of what I could see out of my right eye which at that time I had 20/20 vision in my right eye.

Now 20 years later I need glasses for reading and computer work, I also now need a small correction for distance, saying that most of the time I walk around without glasses. My left eye even with glasses can only see at about 80% of what I can see with my right eye. So what I have tried is progressive glasses that help a wee bitty with the rangefinder patch and I also tried two types of contacts, one in my right eye for distance and one in my left eye for reading...........but that combination really screwed with my head.

I would really like to be able to use a rangefinder without any glasses and maybe even try just a single contact in my left eye to help see the camera dials, but even with my progressive glasses on if I shut my right eye I can only make out the dials 75 to 80% clear.

With your experience with photography and also being an iDoctor is there anything else I could try??

Much appreciation in advance

 

Neil

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