Doesn anyone know how to use diopters to correct for your eyesight?

I shoot medium format cameras, a Mamiya RB67 Pro-S and a BronicaETRS

which come with diopters that can also be changed to almost anything

to suit your eyes. Question is how do you determine what is suited to

your eyes?

 

I wear contact lenses during the day otherwise my glasses at night.

To read I have a pair of reading glasses I use with the contacts

which are +1.25 or I just take my glasses off to read. My script as

written...

 

Sherical

OD -6.00

OS -5.75

 

ADD

OD +2.25

OS +2.25

 

My existing camera eyepieces are both -1.5 but I can get +1.25 or

almost anything else. The question is if my eyes are 20/20 with

lenses or glasses and if I focus with my reding glasses and it's not

working... then what is a -1.25 eyepiece doing for me? That is what

comes with the camera as standard issue.Shouldn't it be zero or do I

need some compensation to see the focusing screen since I do need

reading glasses? What power should I get?

 

I tried removing the dipter and I can't see anything without it. The -

1.5 seems to work but why?... how?

My prescription is -0.50 -1.25 x 95, whatever that means. I asked my eye doctor

what viewfinder diopter correction I would be and he said probably a -1.00. Different

for everybody I guess, but there must be a rule of thumb.

 

This is the first time I can remember anyone asking this question. I guess all the

manufacturers and forum readers assume we all know this stuff. But we don't.

If you're already wearing corrective lenses that give you normal distance vision, you shouldn't need to change from the factory eyepiece in your camera. Just don't use your readers to focus -- the camera is set up to use your distance vision, not your close accomodation.

My camreas check out for alignment but I consistantly get out of focus pictures. I ahve several cameras and get the same fuzz in all. There must be something to diopter corrections. I can't focus with my reading glasses since I don't see anything in the distance with them. I removed the diopter on my prism to see what it would be like if I corrected to my reading glasses diopter and that wasn't any good at all, couldn't see jack squat.

 

There must be some way to calculate or figure out how to correct for diopters.

I had the eye doctor cut a lens for me the same as my right lens for my glasses this helped a lot. I use hasseys with a NC2 finder and this lens just drops in the eyepiece and has a ring to tighted it down, built into the finder. The lens I get cut is the same size as a quarter so I don`t even have to carry my finder to the eye doctor just tell him the size and get him to mark the top , very important! Also it helps shooting square format as your perscription changes when you rotate the finder.

I have some confusion to add to this thread.

 

I have a Mamiya RB that I got used off ebay. Is there a way to tell if the diopter in the magnification thing is something other than zero? Mine seems to be unmarked.

 

If I look through the magnifier without my glasses on (I'm moderately nearsighted) I can't focus the image. If I have my glasses on, I'm fine. Now, I know the obvious thing to do is to just wear my glasses when I focus, but that causes a problem because when I put my eye close to the magnifier, my glasses push it down. This distorts what I see. The compromise is to keep my eye a certain distance away from the magnifier so that my glasses don't touch it, but then I can't quite see the edges of the ground glass.

 

So, is the solution to this to get a a diopter equal to my lens strength? Or is there a diopter in my camera already screwing things up?

 

Thanks

Terry, one solution for you is to roll that eye cup down--it's meant for bare eyes, not glasses. Then, make up your mind about a diopter--which is designed as a FAR focus tool. (that is, if you are farsighted, you may not need a diopter; even though you are physically holding the camera close, the focal "view" is distant.)

 

Confused? Ask your optometrist.

 

Ray Hull

Don't focus with your reading glasses, silly. No, the standard issue is not zero, -1.whatever IS the standard issue. It's just helping you out a little. There is such thing as seeing better than 20/20. The diopter is probably letting you do this. Now go take some pictures and quit fiddling with your diopters.

 

Using a split-screen would help, too.

I have been researching diopters reading all the inforamtion I can find on the interent I found some real scientific answers that gave formulas and examples from eye doctors that really didn't answer my question but sounded so impresive to make you think there was an answer in there only you didn't understand it, so it flew right over your head. It seems their calculations came under fire by some other experts and got shot down with more calculations that meant nothing in the long run.

 

After reading tons of information I came across this one paragraph in a forum that just made it all real. It seems the viewfinders of most cameras are designed to focus to a virtual 30" which is actually your focusing screen's ground glass. It's like the drive in movies, you don't focus on teh projector but the screen no matter what that distance is. That's it!... the ground glass is all you have to be concerned about getting sharp. The paragraph below tells how to make the adjustments by substitution till you get it right, regardless of what the experts have calculated.... this is it....

 

 

From Mediium Format Digest...

 

From: "Byron Marr, D.O." buzzmarr@onramp.net

Newsgroups: rec.photo.equipment.medium-format

Subject: Re: EyePiece Diopters

Date: Mon, 06 Jul 1998

 

" Well take the lens off and point the camera to a light subject..white wall..looking through it and then try diopters until you get the "grain" of the focusing screen in focus. You should see a more clear type of grain..like the grain focus while enlarging..when you are in focus. This is obviously for the screw in type of diopters and no the factory modified prism therefore you will need to go somewhere that carries the diopters and try them."

I talked to a Tech at Canon for this very situation a couple of weeks ago for a customer of mine. He told me that all cameras are set up for -1.0 at the factory. Also, you need to take your camera to your optometrist and the camera is tested without its lens. When you receive your prescription , you would subtract 1.0 from the results and that would be the diopter that you should get. Mind you that optometrist testing diopters are more fined tune in increments of 0.25 or finer. Camera diopters come in half increments only for example: -2.0, -1.5, -1.0, -0.5, 0.0, +0.5. For further information, you may call your camera's manufacturer Tech Dept.

Take your camera & tripod to the eye doctor. Remove the diopter. Let the dr put different strength lens where the diopter normally goes until you get it right. He will probably check your chart and if you know the # of your current diopter, he will probably get it right with the second lens.

What a bunch of ignorant blather. First of all if you need bifocals for reading then using just your distance contacts will *not* in most cases be sufficient since the viewfinders of most cameras are set a a "virtual" distance which is typically anywhere from 1 to 2 meters. Your "ADD" is 2.25 yet you are comfortable reading with 1.25 reading glasses (which is 1 full diopter less "ADD" than your Rx). That means either your Rx ADD is way too strong or else you tend to read at arm's length.

 

So, here's what to do: Put in your contacts and take your camera with you to the drug store where they sell generic reading glasses. With the lens off the camera, try on various powers from +0.25 to +1, see which of them lets you see a crisp image of the markings on the GG screen. That's the diopter you should then order--assuming you will wear your contacts. To determine what correction diopter you would want to use without your contacts, add the number of the reading glasses you chose to the distance number from your Rx for that eye (eg. -6 + 0.75= -5.25). OD= right eye, OS=left eye.

Did you contact Mamiya & Bronica? They should have a guide.

 

I took my 500C with me to my eye doctor. He just laid diopter lense on top of the WLF magnifier until we found one that worked. My reading glasses are +2.5. The best dioter for focusing my Blad was +2.

 

You could also go visit a large camera dealer and try varios dioters until you find the one that is best for you.

 

My 'snoot' for the Hasselblad has an adjustable dioter that when I use it I just turn it until I get the best focus.

Paul,

 

I believe you are talking about the lens for the WLF. I think it just acts as a loupe for the ground glass.

 

I was at the camera shop and the sales assistant let me test what they have. Then I found out that 0 was not 0. Anyway I bought the one which I thought gave me the most comfortable viewing and easy focus.

"" What a bunch of ignorant blather. First of all if you need bifocals for reading then using just your distance contacts will *not* in most cases be sufficient since the viewfinders of most cameras are set a "virtual" distance which is typically anywhere from 1 to 2 meters. Your "ADD" is 2.25 yet you are comfortable reading with 1.25 reading glasses (which is 1 full diopter less "ADD" than your Rx). That means either your Rx ADD is way too strong or else you tend to read at arm's length. ""

 

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Excuse me Jay? Your thoughts are a bit late AND simply repeating what has already been established, aside from you wonderfully profound "blather" remark.

 

Yes, view finders are focused to 1 meter ( 30" was quoted), was already established. Yes, taking off the lens to see the GG was already quoted from Medium Format Digest, not authored by you. Yes the +2.25 is my Rx and yes I use a +1.25 reading glasses, all was correctly quoted.

 

The reading glasses I use are comfortable for reading topo maps, while the +2.25 gives me eyestrain. Regardless, that is what was written on the Rx and what I am using... given as accurately I as i could. Perhaps a qualified eye doctor can explain or calculate my diopter Rx based on that data. Perhaps the ADD is over correcting for my progressive bifocals? perhaps it was given that way just to piss you off?

 

Now Sir, if your very scientific theory is correct, substituting "off the shelf reading glasses" is the way to adjust my viewfinder... then please explain why substituting "off the shelf reading glass" only renders a blur even when removing the -1.5 diopter form the prism? Don't you think that was already mentioned here in another message? It seemed to work for someone else with a similar problem with a different Rx. Did you read the thread at all? Oh but of course you had already made up your mind this was only "ignorant blather" when you saw the headers.

 

BTW: It seems the drug store down the block here in NYC only has positive diopters in increments of +0.5, starting at +0.5 on up to +6. It also seems a negative diopter does correct my focusing on the GG despite my using a positive reading diopter according to my ADD of +2.25. I did try using a +0.5 and +1 to give me an effective -1 to -0.5 with the -1.5 installed, it didn't help at all and made matters worse. So based on my experimentation I find a negative diopter is needed to correct my vision, besides here in NYC we have very qualified eye doctors which i will ask for a professional opinion later this week and will follow up on this thread... if that's ok with you?

 

SOOOO.... Please explain, in your infinite wisdom, why positive diopters don't work but yet the negative diopters seem to help? Otherwise stop polluting this space with YOUR ignorant blather if you can't contribute anything intelligent. I'm not an eye doctor nor am I an expert. If I knew the answer I wouldn't have asked for help. So Jay, take hike and spew your crap someplace else pal!

 

 

 

HC, thanks, I am using a prism on both cameras with a -1.5 diopter installed from the factory. I was using my LF loupe to focus the GG when I did have the WLF on but changed t a prism since I wa told it would help. I will have my Doctor adjust my eyepiece with his selection of lenses, then buy the apropiate diopter from Bronica and Mamiya to bring me up to speed. I learned that the zero is really a -1 as installed at the factory. Thanks for the help.

The rectangular viewfinder diopters for the Mamiya 6 and some of the prism finders are marked with dots. Red dot is +, white dot is minus, number of dots = number of diopters (they don't have even half diopters in this product range).

 

As to choosing one, I recommend trial and error. My right eye prescription for distance vision is -1.75 spherical and zero cylindrical, so I am lucky that an ordinary off the shelf diopter should suffice. For Nikon SLR, the best for me is -2.75 (for cameras with adjustable diopter in the viewfinder) or -3 off the shelf for the simpler cameras. For Leica M6, -2 in their range is best. For Mamiya 6, -1 is the best choice.

 

Why the difference? Something to do with the viewfinder optics I suppose. Incidentally, my choices above were done and refined very carefully over much testing. Low light situations are the most critical, and therefor best for testing.