Bessa R diopter eyepiece calculation?

[ChrisPlatt]

I am slightly nearsighted and normally use a -2.0 diopter eyepiece on my SLR.

SLR viewfinders are normally -1.0 without correction.

Are rangefinder camera viewfinders normally 0 (zero)?

If so, given that diopter rating of eyepiece is cumulative, am I correct to assume
I will need a -3.0 diopter eyepiece to achieve the same effect on my Bessa R?

TIA,
Chris

 

[JohnL]

I'm really confused about this too. I got a +3 diopter eyepiece for my SLR, because that is roughly the prescription of my reading glasses. It's hopeless ... far worse than the standard eyepiece. For distance, I need specs about +1 diopter. Maybe this is the eyepiece I need. However, my other SLR eyepiece is adjustable from -3 to +1, and it's just fine at +1. So maybe I need +2 to move my first SLR from -1 to +1. If anyone can help either of us, would be really appreciated. At least this also gives us a bump ...

 

[shaaktiman]

Chris,

This confused the hell out of me when I first got my bessa.

The Bessas don't use any correction in their viewfinders, so if you would normally wear -1 diopter glasses to see (as I do) then you need to use a diopter that has an actual power of -1.

But since most SLRs have a viewfinder that's already at -1 you need a -3 FM10 diopter to get -2 compensation with your Bessa R as you suspected. (Annoying that they label their diopters for total compensation including the Nikon viewfinder instead of the actual power.)

hope this helps,

adam

 

[bluedust]

Thanks for the info guys; I am a -1.75 on my glasses and so roughly a -2. I called Grays of Westiminster ( an exclusive nikon camera shop in london) and they had a -3 dioptre which is really a -2 on a bessa and it is perfect.

Focusing is so much easier; before I bought the adjustment focusing was a little bit of a struggle far away but now it is just fine. There should be a sticky covering this

 

[JohnL]

(snip)
There should be a sticky covering this

Good suggestion. This seems to be a topic that few know the certain answer to and not easy to find out either.

 

[ChrisPlatt]

I ordered the Nikon rectangular -3.0 eyepiece.
I will let you know how it works out...

Excelsior, you fathead!
-Chris-

 

[JohnL]

If I understood all this correctly,
- SLRs are based on a standard diopter of -1
- RFs are based on a standard diopter of 0
The diopters themselves are numbered according to what your eyesight requires for normal (not reading) prescription glasses (not on the shift from the camera's base to your prescription).
So if you are using an RF diopter on an RF camera, or an SLR diopter on an SLR, you get the same number as your prescription.
However, and here's the gotcha, if you are using an SLR diopter on an RF camera, like a Nikon SLR diopter on a Bessa RF camera, you need a diopter that is different by 1 from your prescription. If your prescription is -2 (for example) you will need (I think) a -3 SLR diopter on an RF (like ChrisPlatt and shaaktiman said). What then if your prescription is +1? Would you need a zero (SLR) diopter correction, which is actually a +1?

 

[ChrisPlatt]

I got the Nikon rectangular diopter eyepiece this week.
It is brand new, in original gold Nikon box.
It says "F-501" on it.

Frame slides on and fits snugly - a perfect fit.
Glass is slightly larger than bezel on Bessa eyepiece,
so there should be no vignetting problem.

The difference is not as dramatic as I expected,
but it does seem to be easier to focus near objects.
Distant objects still seem slightly blurry, especially in dim light.
Perhaps this is because of finder magnification (i.e. lower than an SLR),
or maybe these 45-year-old eyes are just getting tired...

"Excelsior, you fathead!"
-Chris-

 

[ChrisN]

There's a good article about this diopter business in Andrew Nemeth's Leica FAQ



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