A simple diopter question...

M Carter · Jul 16, 2020

I've done a lot of web-research on this, but can't find a specific answer...

I wear contacts due to bad near-sighted-ness - my distance visions is really poor. And for some years now, I've used +1.5 readers for close work, while wearing my contacts.

So all the info I've found on-line seems to be based on looking at your RX - but I'm not trying for overall correction - I shoot with my contacts on - just need to figure out "what diopter would function like a +1.5 reader?" The only clue I have is that on my DSLRs, I seem to be using more "+" compensation on the adjustment wheels, but those aren't really marked as to the baseline. I'm mainly looking for my RB WLF and prism.

Donald Qualls · Jul 16, 2020

The optics in the viewfinder make the ground glass seem further away than the couple inches it actually is. For your RB, however, you don't have that in the WLF, other than the focusing magnifier. I don't have a prism (yet) for my RB67, so can't comment on that, but you won't want as much compensation as your readers for the prism because it already has some -- most are around +1 equivalent, to make the ground glass "look like" one meter away. That would mean you only want/need about +0.5 added to that for the prism, but you'll want your full reading prescription (probably your regular readers) for the WLF, if not a bit more (depending on what distance you usually view the WLF) -- but you won't need the readers when using the magnifier to focus, of course (at least, I used my distance prescription for that with mine).

AgX · Jul 16, 2020

Best way to find out the needed diopter correction for an eyepice is testing. By this evading the sometimes confusing designations diopter-wise by camera manufacturers.
Get yourself some cheap "spare-glasses" of different diopter values. You then can have yourself a correction piece made of same diopter, or try to understand the manufacturers designation and calculate, based on your testing, the needed diopter of an eypiece correction lens offered by the manufacturer.

Fujicaman1957 · Jul 19, 2020

Get a set of close-up lenses and use those to look thru the viewfinder for testing. I had to do this for my Nikon 8008s-it was focusing properly, but my view of the screen was a tad fuzzy. Wound up having to buy a +1 eyepiece off Ebay to get a clear view of the screen.

Sirius Glass · Jul 19, 2020

With my contact lenses I can see clearly through any viewfinder: Nikon 35mm SLR, Hasselblad 45 degree PME, Graflex Model D or Speed Graphic.

AgX · Jul 19, 2020

So, you want to say that we all just have to get your contact lenses to see clearly again?

Sirius Glass · Jul 20, 2020

That sums it up.

voceumana · Jul 20, 2020

Sirius,

That doesn't work for everybody. I can't wear contacts--hard contacts as well as gas permeable ones turn my tears milky. This is a somewhat unusual but documented adverse effect of contacts. My correction for astigmatism is very strong and is not conducive to soft contacts. So I'm stuck with glasses. I can live with it. When I develop cataracts enough to have my eyes' lenses replaced, the ophthalmologist suggests he can make a major reduction in my astigmatism correction, and maybe get close to 20/20 distance vision without glasses. Modern medicine is wonderful!

In addition, I am old enough for presbyopia. Contacts don't readily account for the close distance correction I need for that.

Chan Tran · Jul 20, 2020

You need to add to your camera the amount of diopter that let you see well at 1 meter distance. So if you wear a reader of +1.5 you may not need any diopter. But to be sure ask the doctor for a prescription for 1 meter distance. If not you can try the reader at the store and see which allows you to see well at 1 meter distance.

AgX · Jul 20, 2020

I find it more comfortable and practical to use a rubber eyecup with a integrated correcting lens, than using glasses. However there are not much good correcting-ens/rubber-cup combos and one might have to tinker.

(But when will the enigma be solved, that same camera manufacturers applied diopter-adjustable eyepieces to their cine-cameras, but waited decennias to install this at stilll cameras too, if at all ?)

voceumana · Jul 21, 2020

Diopter corrections do not address astigmatism eyesight issues, so the rubber cup and diopter solution doesn't work for everyone. What I don't understand is why camera manufacturers did not offer rotating custom eyepieces. Leica would grind a custom eyepiece, but as far as I know know one offered a 90 degree rotating mount.

AgX · Jul 21, 2020

Holders for correcting lenses (thus not attachments with alrwady inserted'lenses) all enable you to freely rotate the lens before screwing tight the retaining ring.
Some cameras had such retaining ring, and for slitted eyepiece frames there at least were 3rd party slip-on holders

voceumana · Jul 21, 2020

Yeah, but a freely rotating holder doesn't make the change from horizontal to vertical orientation a quick change for astigmatism correction. What is needed is postitive 90 degree stops or detents.

AgX · Jul 22, 2020

Now I see, you are referring to changing the camera from horizontal to vertical orientation.

You need either two slip-on mounts I hinted at above, in which you inserted the astimatism correcting lens at 90° difference, having to exchange these attachment. Or a right-angle finder, which you can swivel, to which eyepiece you glued the correction lens.

voceumana · Jul 22, 2020

It's just easier and less expensive to use my glasses, even if I have to move my eye a little to see each corner.

StepheKoontz · Jul 22, 2020

voceumana said:
It's just easier and less expensive to use my glasses, even if I have to move my eye a little to see each corner.

I've found for me that while a -2.0 diopter isn't always a perfect correction, it's close enough to be usable. And for a camera without good eye relief, is preferable to trying to use wearing glasses.

Alan Edward Klein · Jul 22, 2020

I always wear my progressive eyeglasses. There's some movement of my head to find the right focus point when looking through RB67 eyefinder with the magnifier attachments or the waist level with or without its magnifier. Since I need glasses to see generally, it's just too much trouble to remove my eyeglasses each time I want to look through the camera and then put them on again to to see otherwise.

AgX · Jul 22, 2020

voceumana said:
It's just easier and less expensive to use my glasses, even if I have to move my eye a little to see each corner.

Resting a camera at ones forehead/face is one means of camera stabilisation. That does not work with glasses on.

wiltw · Jul 22, 2020

voceumana said:
Sirius,

That doesn't work for everybody. I can't wear contacts--hard contacts as well as gas permeable ones turn my tears milky. This is a somewhat unusual but documented adverse effect of contacts. My correction for astigmatism is very strong and is not conducive to soft contacts. So I'm stuck with glasses. I can live with it. When I develop cataracts enough to have my eyes' lenses replaced, the ophthalmologist suggests he can make a major reduction in my astigmatism correction, and maybe get close to 20/20 distance vision without glasses. Modern medicine is wonderful!

In addition, I am old enough for presbyopia. Contacts don't readily account for the close distance correction I need for that.

Agree. 'Get a pair of contact' does not work for all, it does not work for me!

With my old eyes, contact lenses correct my nearsightedness for distant vision...but if I look in a viewfinder with no diopter correction (what a 20 year old would use) I cannot read in-viewfinder displays clearly nor do I see the focusing screen clearly enough to detect sharp focus! Only if I dial in a diopter adjustment value (on a camera that has diopter adjustment) can I clearly see displays in the viewfinder and detect sharp focus...If I use drugstore reading glasses of +2.0 diopter (in lieu of a camera adjustment) I can read newsprint clearly or view an unadjusted viewfinder.

Folks over 50 often have lenses in their eyes that are not sufficiently flexible to change curvature via the muscles in the eye enough to read well, compared to distant vision. The hazards of old age...arms that are too short for reading. In my case, I can still use 'monovision' to avoid bifocals or drugstore readers...the right eye is adjusted with contact lens for distance, and the left eye is adjusted with contact lens for reading.

wiltw · Jul 22, 2020

M Carter said:
I've done a lot of web-research on this, but can't find a specific answer...

I wear contacts due to bad near-sighted-ness - my distance visions is really poor. And for some years now, I've used +1.5 readers for close work, while wearing my contacts.

So all the info I've found on-line seems to be based on looking at your RX - but I'm not trying for overall correction - I shoot with my contacts on - just need to figure out "what diopter would function like a +1.5 reader?" The only clue I have is that on my DSLRs, I seem to be using more "+" compensation on the adjustment wheels, but those aren't really marked as to the baseline. I'm mainly looking for my RB WLF and prism.

The problem is 'converting' your Rx for reading into a diopter value for the eyepiece...manufacturers to not all use the same procedure in naming their diopter eyepieces! Assuming your reading vision requires diopter +1.5 for clear reading (strength compared to your standard correction for distance (like diopter -4 for distance)...you need for +1.5 offset from distance means that your eye needs true diopter -2.5 for reading vs. -4.0 for distance

One group might have standard eyepiece being a true diopter +1, and if you need a stronger substitute eyepiece you buy their +1.5 (stronger relative to the standard eyepiece)
Another group might have standard eyepiece being a true diopter +1, and if you need a stronger substitute eyepiece you buy their +2.5 (true diopter value)

The trick is to find out which of the two conventions is followed for your camera brand!

AgX · Jul 23, 2020

That is why I proposed to use cheap (provisional) glasses to test for the best diopter.

(of course, when one then not uses a custom or loose lens, but the readymade attachment by the camera manufacturer, one still has to understand how they designated that attachment... or probe again)

Donald Qualls · Jul 23, 2020

wiltw said:
In my case, I can still use 'monovision' to avoid bifocals or drugstore readers...the right eye is adjusted with contact lens for distance, and the left eye is adjusted with contact lens for reading.

Many people seemingly find this an acceptable solution, even to the point of permanently altering their eyeballs (Lasik) into this "monovision" configuration, or getting this setup with the implant lenses after cataract surgery.

And some do not. I use both eyes for almost everything, need useful depth perception both for scale focusing on cameras that need it and for close work (installing o-rings into inside grooves, for instance). Monovision correction would leave me feeling crippled, like being half blind and unable to even mentally correct because I can see from opposite eyes in different situations. "Takes time to adjust" -- sure, just don't try to drive home after getting the lenses. Nope, not happening for me.

M Carter · Jul 23, 2020

wiltw said:
The problem is 'converting' your Rx for reading into a diopter value for the eyepiece...manufacturers to not all use the same procedure in naming their diopter eyepieces! Assuming your reading vision requires diopter +1.5 for clear reading (strength compared to your standard correction for distance (like diopter -4 for distance)...you need for +1.5 offset from distance means that your eye needs true diopter -2.5 for reading vs. -4.0 for distance

One group might have standard eyepiece being a true diopter +1, and if you need a stronger substitute eyepiece you buy their +1.5 (stronger relative to the standard eyepiece)

Another group might have standard eyepiece being a true diopter +1, and if you need a stronger substitute eyepiece you buy their +2.5 (true diopter value)

The trick is to find out which of the two conventions is followed for your camera brand!

That's more what I'm hoping to find... so after your paragraph saying "+1.5 offset my eye needs a true diopter -2.5" and so on... and then standard eyepiece and I need a +1.5 or +2.5... not sure if I'm reading this properly, but in the simplest terms - if I need a +1.5 reader for reading and 1-meter-ish work, then I need something around a +1.5 diopter, depending on how the manufacturer dealt with it??

AgX · Jul 23, 2020

Canon for instance designated their correcting attachments so hat they tell the resulting diopter of the whole eyepice.

wiltw · Jul 23, 2020

M Carter said:
That's more what I'm hoping to find... so after your paragraph saying "+1.5 offset my eye needs a true diopter -2.5" and so on... and then standard eyepiece and I need a +1.5 or +2.5... not sure if I'm reading this properly, but in the simplest terms - if I need a +1.5 reader for reading and 1-meter-ish work, then I need something around a +1.5 diopter, depending on how the manufacturer dealt with it??

The simplest thing is to find out which strenth diopter is needed to make your distance vision into 'reading' distance...if you try out reading glasses in the store, you read text provided on the display rack, and then discover "I need +2.5 diopter reading glasses".
...but understand that most viewfinders use 30-36" apparent reading distance, and you might stand at a different distance in front of the test text display (where 30-36" is too far for our arms to hold the book!)
The more complex thing is to figure out (assuming the standard eyepiece is +0.5 diopter, you need to buy something +2.0 diopter stronger than the standard eyepiece,)

do you buy '+2.0' labelled eyepiece (relative strength) accessory, or
do you buy '+2.5' labelled eyepiece (absolute diopter strentth) accessory?

It depends on the camera manufacturer!!! Hopefully the original owner manual for the camera sheds some light on the topic in the Accessories descriptions.

A simple diopter question...

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