How do you know which diopter to use ?

[hjoseph7]

<p>I have one of those little diopter dials on my DSLR, but I'm not sure if I'm at +1, +2 or -3. I just turned the dial until everything is in focus. Now I need to get a diopter lens for my manual camera because trying to focus with glasses on, is a big PITA. The only problem is I'm not sure which diopter lens to get and my local shop does not carry them so I have to order online. Is there any way to tell by looking at the dial on your DSLR or some other method ? I have a Canon camera. </p>

[Spearhead]

<p>What is the strength of your glasses? That will tell you.</p>

[sarah_fox]

<p>Just call your opthamologist or optician. They should have your prescription on file. If you have +2 eyeglasses, for instance, you'll need a +2 diopter attachment.</p>

<p>If you're far-sighted, you can determine your prescription by focusing a spot of sunlight on the ground through your eyeglasses. Measure the distance in meters between your lens and the ground, at which you get the best focus. Divide 1 m by that distance, and that will give you the diopter value of your lens. For instance if your lens focuses the sun at 0.5 m, you have a +2 diopter lens. This of course assumes you don't have bifocals or something, in which case you'll have to mask off the relevant area of your lens.</p>

<p>Another way to see what works, again if you're far-sighted, is to use close-up "filters" to see what corrects your eyesight the appropriate amount. Those "filters" (really lenses) will be marked with their diopter rating.<br>

</p>

[SCL]

<p>You can go into your local drug store/pharmacist and check the reading glasses which are marked in actual diopters. Just be aware that some older cameras have their viewfinders with a built in -0.5 diopter. Usually if you are using the OEM diopters, once you know what strength you need, you order the manufacturer's stated diopter and it takes into account the -0.5 of the viewfinder (for instance with these cameras if you needed a +3, you would order a +3 knowing it would actually be a +3.5). This is one place where reading the fine print in the specs pays off in not enduring endless frustration (I went thru this stupid exercise years ago with a camera and ended up with 3 accessory diopters before finding which one which worked for my eyesight). These days I wear my eyeglasses all the time, so on some (-0.5) bodies I need a +0.5 correction; the mfrs offer what they call a 0 diopter which does the trick (since I want to bring the result to zero for my glasses).</p>

[chris_waller]

<p>I'm long-sighted and have a +2 prescription. The eyepiece on my Nikon FMs is, I believe, +1 dioptre so I have a +1 correction lens to get everything sharp. Sadly I can no longer get correction lenses for my Canon F1s so focussing with them is difficult and slow.</p>

[jcuknz]

<p>I like Stephen's suggestion although I would take the manual camera with you and try various glasses until you get the correct one. If you look for the cheapest ones they are probably plastic rather an glass and can be easilly cut and sanded to fit the eye-piece of the camera if you are at all a DIYer like me :-) There are adhesives on the market which do not 'flood' over the plastic they are securing and craze the plastic ... I use it for fixing windows etc in my modelling ... trains planes buildings etc.</p>

[Jochen_S]

<p>There is a lot you can guess at home, but nothing beats the eyes on and test lens in measuring glasses experience at your optometrist. That shop offers a "we grind your prescription into *what you want*" service. And when they measuring your eyes for infinity they have not much extra hassle to do one for viewfinder too.<br>

That being said: You surely have an old pair of spare glasses you can take apart or a lens that got replaced in a more or less current spectacle frame with known prescription and an old +1 close up lenses for some camera? Why not test at home with those stacked?<br>

Keep in mind that few people have a just spherical prescription. Those needing an extra cylinder need it at a certain angle. Give the old lens you are testing a 90° turn to 9 o clock and check out what you'd see shooting in portrait orientation. - Will you get away with just 1 diopter lens or need two? - IMHO its really sad that no camera manufacturer offers a 90° rotation option for viewfinder diopters.<br>

When you are testing at home try to watch at least the news on TV through your camera to make sure the correction you picked is for comfortable instead of as close as (temporary) possible viewing distance.</p>

[hjoseph7]

<p>OMG - This might be a long process. I'll try the drug store thing first, if that doesn't work I'll call my optometrist(who ever that is) , thanks. </p>

[jim_momary]

<p>Chris -</p>

<p>They come up often on Ebay.<br>

A search using "Canon F1 eyepiece diopter" brings up 5 listings at this moment, tho none are +1.</p>

<p>Just keep a watch and I'm sure you'll find one. Works for me (usually) :o)</p>

<p>Jim</p>

[blumesan]

<p>A visit to your optometrist is the surest solution.</p>

<p>Failing that, trying out reading glasses in your local drug store is a good solution, but keep this in mind: choose the glasses that allow you to read comfortably when reading printed matter held at about arms length** (actually at 1 meter), not something held at your normal reading distance (which for many is significantly less than half a meter). </p>

<p>**Reason: all SLR viewfinders incorporate a negative lens to place the virtual image further from your eye than the actual distance between your eye and the viewing screen (which is only an inch or so, give or take). Nikons use a -1 diopter lens, to place the image at 1 meter which is a comfortable viewing distance for someone with normal vision.</p>

<p> </p>

[Matthew Currie]

<p>I have found that though I use about a 2 1/2 or even 3 for reading glasses, a +1 is about all I need for a camera. Not too long ago I ordered a used diopter for my F3 and, fortuitously, it was packed along with a +3. Despite being pretty farsighted, that +3 was too powerful for me to focus at all.</p>

<p>The eye accommodates a little, and I'm not sure how finely you have to cut it. One possibility if you have a variable diopter camera, is to look at the specs and see what the range is. Nikon includes that in its specs, and it varies from one model to another. I don't know how linear it is, or if the center point is actually central, as some models go to higher negative numbers than positive. But if you can figure out where the center point is, you can divide up the distance between that and the limit, and get pretty close. And of course, if your chosen point is at or near one of the limits, you will know what it's set at. </p>

[chris_waller]

<p>Jim, thanks for that. I'll take a look.</p>

[q.g._de_bakker]

The optometrist will probably have a number of small lenses you can put over the eyepiece and try. Just give it a go.

[roger_bergeron]

This msg is late to the party, but this question may haunt those hobbyists who treasure legacy film Nikon cameras….

Nikon has a publication which speaks direct to the Nikon-specific camera diopter situation, named “Nikon SLR Camera Viewfinder Eyepiece Application Reference” (I am looking at version revision which was updated on September 17, 2004”

It is true that Nikon SLR cameras (without a built-in adjustable eyepiece correction have a base diopter value of minus one.

A clear eyepiece will result in a minus 1.

If you replace the clear eyepiece with a plus 3, the end result is a plus three… (the base -1 is taken into account in labeling the replacement eyepieces)… no math required)

Nikon publication also states:

To determine which Nikon diopter is best for you, see an ophthalmologist, optometrist, or a dispensing optician. Ask them to determine your specific diopter, based on your corrective prescription when viewing an object at a distance of approximately 1 meter. Then base your Nikon diopter purchase on this diopter value.

End.

[JDMvW]

I just turned the dial until everything is in focus.

 

Probably since 2014, the problem has become moot, but in any case, the "just turned the dial until everything is in focus" approach still works since the most important variable in the equation is the user's vision.

[SCL]

Since this was resurrected I thought I'd add a solution I stumbled across. No dealer near me has one of these or diopters to try out...up to the point I got this it was either a trip to the eye doctor or switching among one or two diopter clip ons I had on hand, sometimes combining them for a final guesstimate. I came across this

on the big auction site for a pittance...it clips onto most eyepieces of older cameras and one rotates the dial across the various diopters until things become clear, then you read the strength of the diopter needed. It isn't perfect in that the selection is limited, but it will get one into the ballpark if unsure about a diopter. If the camera's eyepiece isn't compatible (eg Leica M series bodies), you just put the camera on a tripod and hold the rotating dial in place as you go thru the various diopters. This one was specifically designed for Canon bodies, but I've used it on a wide variety of bodies including Contax, Pentax, Ricoh Yashica and Leica.