Help please! ...finding the right diopter correction value!

[Frank Fremerey]

OK. I now want to buy or have made the diopter correction for my FM2. My fathers knows some online shops where they sell these prefabricated for cheap.

I will just have to buy one, use one of the original nikon screw in lenses as a donor for the 19mm-ring and done.

But now: how do I find which strength I really need?

My idea:

I could count the clicks on the D600/D3/D500 until I get the best result with the builtin correction.
Can I use this value(s) to deduct the best coorrection for the FM2 screw in diopter???

Please help.

Thank you!

[Frank Fremerey]

I got 16 clicks on the D600. If I turn the knob completely to the left and click clockwise I am best at click #9
I got 6 clicks on the D500. If I turn the knob completely to the left and click clockwise I am best at click #3
I got 12 clicks on the D3. If I turn the knob completely to the left and click clockwise I am best at click #6
what is the range and what are the steps?



Sitting in front of my computer screen I need a chapo correction of +1.5 will do

Reading a book or on a smartphone my expensive custom glasses +2.25 are much better

[Les Olson]

OK. I now want to buy or have made the diopter correction for my FM2. My fathers knows some online shops where they sell these prefabricated for cheap.

I will just have to buy one, use one of the original nikon screw in lenses as a donor for the 19mm-ring and done.

But now: how do I find which strength I really need?

My idea:

I could count the clicks on the D600/D3/D500 until I get the best result with the builtin correction.
Can I use this value(s) to deduct the best coorrection for the FM2 screw in diopter???

There is a table at https://support.nikonusa.com/app/answers/detail/a_id/639/~/viewfinder-diopter-adjustment 

From the table, if your prescription is +2-ish you need the +1 correction lens.  If you have a lot of astigmatism that will only correct the centre of the field - but that should be fine for focusing.

[Frank Fremerey]

I bough the
0 and the +1
They do not work.
I need a custom made glass.

[Frank Fremerey]

Any idea of how to deduct the value from tze clicks?

How much correction per click???

[Bjørn Rørslett]

The camera manual provides the dioptre range. Assuming a linear relationship, just divide by the total clicks to get an estimate of delta dioptre per click.

[pluton]

You could bring the camera to an optometrist.  Explain/demonstrate your needs and the 'apparent distance' idea.  I have seen Optos that have small handheld test lenses that could be held between the finder and your eye.

[aerobat]

Hi Frank,

I really hope you'll soon find the right diopter. Bringing it to the optometrist could be worth a try.

Cheers Daniel

[Frank Fremerey]

Thank you Bjørn. I assumed a linear relationship, but...

Trouble is the lenses are glued to the screw in aluminium...

[David H. Hartman]

Frank,

You need a correction lens for an optical viewing distance of 1.0 meter (39.37") for a Nikon or Nikkormat from the Nikon F to the Nikon F5 and FM/FE family to the FM3a. The F and F2 and FM/FE to the FM3a all use the same size. The finders on all of these are without a correction lens -1. If you needed a custom made 0.0 diopter correction you would add a +1.0 diopter (not Nikon's +1) as -1 +1 = 0.

If your ophthalmologist or optometrist told you that you need a +1.5 diopter correction to view an object at 1.0 meter you would need a generic +2.5 diopter eyepiece (+2.5 -1 = +1.5) not Nikon's 1.0 or 2.0. Nikon's eyepieces are marked with the combined diopter as in -1 (body) +1 eyepiece is marked 0.

If you call your ophthalmologist or optometrist he/she can calculate the correction you need for 1 meter. Then you factor in the standard Nikon -1 diopter if having a custom eyepiece made or ignore it if buying a Nikon eyepiece. The fly in the ointment is astigmatism. If your persecution includes astigmatism it will include cylinder if I remember correctly. If it's slight it can probably be ignored. If it's strong it's a problem. The astigmatism corrected eyepiece will have to be aligned correctly and it will need to swivel 90 degree for horizontal and vertical. Marty Forscher did a modification for a Nikon F2 or F3 for a swiveling eyepiece for astigmatism. I think there is a link here at NikonGeard.net showing a camera with this modification.

I have a Hasselblad 500CM with NC-2 Prism and a custom eyepiece ordered and delivered by my ophthalmologist with astigmatism correction. The Hasselblad 500CM has a mind controlled rotating back so the camera is never turned. With that eyepiece and an Acute-matte D screen the viewfinder is as pleasant to view and focus as my Nikon F3. I couldn't focus it with the standard eyepiece in the NC-2. I had to take the NC-2 off to focus.

Talk this over with your ophthalmologist or optometrist. I hope this helps...

Dave

[David H. Hartman]

I bough the
0 and the +1
They do not work.
I need a custom made glass.

Can you try a Nikon +2 at a camera dealer? You may need a +1.5 or maybe something like a +1.25 with astigmatism correction. As suggested above you might take the camera with you to your eye specialist. 

Dave

[Frank Fremerey]

Dave. Thank you. Ok. And if I get the right lens, how do I mount it? 

My father says it is 80 Euros machine setup cost to manufacture the 19mm screw in ring without without the lens.

It is much easier and cheaper for me (20 Euros) to get the Nikon +2 and try it.

[Matthew Currie]

The old F diopters I have appear to have the glass elements swaged in.  In other words, the inside edge of the brass shell is crimped over the edge of the glass to hold it in.  If it costs that much to machine a new ring, I suspect you'd be better off buying one even if it comes out wrong.  If it does not work, punch the glass out and use the frame.  If you can't swage it again, glue it.

[Hugh_3170]

May be there is a half way house approach - take an old Nikon eye piece and have the machinist / lathe operator carefully machine away the swaged area of the eye piece and prepare a seat for the new prescription lens, which can then be glued in.  Alternatively the machinist could cut a groove for a retention ring or circlip.  Since no fine thread cutting is involved with this approach, machining costs should be significantly reduced.

In my case, my left eye is significantly better than my right eye, and sometimes I use it instead of the right eye when I am trying to achieve critical focus.  It is awkward, but doable.  Might be worth trying if that is also true in your case - at least it might give you an indication of whether it is an eye issue or a camera issue that you are dealing with.

Good luck.

[pluton]

Excellent, technically coherent suggestions in the preceding posts.
There is one ultimate alternative:  Get a film cam that is HP finder equipped and shoot with your glasses on.