Use of corrective diopter lenses

[Frank2122]

Hello
a fairly basic question - on a Nikon F2 (or an FM), if using a corrective diopter, do I remove the one in the camera body and replace it with the corrective, or do I stack the corrective on top of the original?

 

[Chan Tran]

For the FM you have to remove the plain glass one. I think the F2 doesn't have come with the plain glass one (I haven't had the F2 for so long).

 

[Nicholas Lindan]

You remove the original and replace it with the new diopter lens.

 

[Frank2122]

Thanks

 

[MattKing]

Thread title tweaked, because technically a diopter is a measurement, not a lens.
And yes, I know that that is picky, but as many of the membership have first languages that are not English...

 

[FredR]

...technically a diopter is a measurement, not a lens....

A few months ago, I had my annual eye examination and was given a script for new eyeglasses (both distance and readers). After the ophthalmologist was finished, I showed him a printout of Olympus's diopter chart (click on image, below) and asked which lens applies to me. He seemed a bit surprised as he looked at it, but then said it would be lens -1 or -2. I bought a used eyecup with -2 lens and slipped it onto my OM-1N. My sight through the viewfinder became worse. Maybe he quoted numbers from the wrong column.

I'm wondering whether to bother finding and buying a -1 lens, since in retrospect my eyesight isn't all that bad. (I've set my other OM bodies's built-in diopter adjusters, but I have no idea where "neutral" began.)

Can diopter be calculated from an ophthalmologist's eyeglass script?

 

[wiltw]

A few months ago, I had my annual eye examination and was given a script for new eyeglasses (both distance and readers). After the ophthalmologist was finished, I showed him a printout of Olympus's diopter chart (click on image, below) and asked which lens applies to me. He seemed a bit surprised as he looked at it, but then said it would be lens -1 or -2. I bought a used eyecup with -2 lens and slipped it onto my OM-1N. My sight through the viewfinder became worse. Maybe he quoted numbers from the wrong column.

I'm wondering whether to bother finding and buying a -1 lens, since in retrospect my eyesight isn't all that bad. (I've set my other OM bodies's built-in diopter adjusters, but I have no idea where "neutral" began.)

Can diopter be calculated from an ophthalmologist's eyeglass script?

Yes, but the complication may be that the standard eyepiece has a diopter value, and the way that the manufacturer identifies corrective values are expressed as 'additional' rather than absolute diopters, and there is no standard for expressing it from one manufacturer to another. Additionally, the typical camera viewfinder is set up with a virtual distance of 30" or maybe 1 meter, and not a single standard followed unversally. And, your optometrrist may not know that camera viewfinders are not 'at Infinty' but are at an intermediate distance (and also not 'at reading distance').

Let me explain further...

Assume that two manufacturers both put a -1 Diopter eyepiece on their camera, and that the focus screen viewed has a virtual distance of 1 meter. If YOU need +2 corrective value, one manufacturer labels its +2 corrective eyepice as '+1' ('-1' plus '+2') or the final Diopter value, while another manufacturer labels the corrective eyepiece it '+2' (the corrective change value). From one, you seek '+2' but from the other you seek '+1'

For your viewing eye (the one that looks thru the viewfinder), show us the Diopter value for your vision at distance, and for your vision for reading (what is written on the prescription)...and we can translate.

 

[FredR]

...Assume that two manufacturers both put a -1 Diopter eyepiece on their camera, and that the focus screen viewed has a virtual distance of 1 meter. If YOU need +2 corrective value, one manufacturer labels its +2 corrective eyepice as '+1' ('-1' plus '+2') or the final Diopter value, while another manufacturer labels the corrective eyepiece it '+2' (the corrective change value). From one, you seek '+2' but from the other you seek '+1'....

It seems to me that that Olympus deals with that in their diopter chart (above), even though I didn't understand it. Thank you for your explanation.

For your viewing eye (the one that looks thru the viewfinder), show us the Diopter value for your vision at distance, and for your vision for reading (what is written on the prescription)...and we can translate.

Right (viewing) eye, from the doctor's script: sph: plano cyl: +0.75 axis: 170 add: +2.75

I only just looked up the meaning of plano, so perhaps I need no diopter correction at all.

 

[Petrochemist]

Thread title tweaked, because technically a diopter is a measurement, not a lens.
And yes, I know that that is picky, but as many of the membership have first languages that are not English...

Surely diopter is a measurement of lens strength. IIRC diopter is 1/focal length in meters.

 

[Petrochemist]

Can diopter be calculated from an ophthalmologist's eyeglass script?

The script is in diopters. Unlike focal lengths diopters can simply be added to get the effect of two lenses used together.
The script will show the infinity diopter, followed by a cylindrical component & the angle it is added at, followed by the addition correction for reading.
When I was getting prescription safety glasses supplied by work I opted for an intermediate addition so that they gave me stress free focus at arms length (for computer screens mainly)

 

[MattKing]

Surely diopter is a measurement of lens strength. IIRC diopter is 1/focal length in meters.

It is.
But it isn't a thing - in this case a lens you can buy. The original thread title referred to "Use of diopters".

 

[wiltw]

It seems to me that that Olympus deals with that in their diopter chart (above), even though I didn't understand it. Thank you for your explanation.



Right (viewing) eye, from the doctor's script: sph: plano cyl: +0.75 axis: 170 add: +2.75

I only just looked up the meaning of plano, so perhaps I need no diopter correction at all.

It is Plano for DISTANCE, but your viewfinder has an apparent distance which is about 30" (or 39")...and the +2.75 is the correction that you need for reading books, about 12" away. I would say that intermediate distance reading would be about +2 Diopter for you (or maybe +1.75, but not +2.75...stronger is for closer, which is not what you need for a camera viewfinder)

 

[psmithp]

I discovered that using my reading glasses helped a lot. Much easier than getting correction lenses that have not been manufactured for half a century.
But maybe you can get them unfitted from AliExpress or Wish and somehow fit them yourself?