Which Diopter Do I Need PME51 ?

[jon_kobeck1]

I recently bought a PME51 for my Hasselblad 501C and it came with a +1 diopter. I cant focus, the image is blurry. I

occasionally wear glasses but not always. I can see fine without glasses. I thought the +1 diopter wold simply magnify the

image a bit more for me.

Any suggestions?

[danny_wong2]

<p>Go to your optician with your camera and he can try diopter correction lenses for you at different factors.<br>

You need to decide if you want to focus with your glasses on or off since that will affect the correction factor</p>

[john_stockdale2]

<p>"I thought the +1 diopter wold simply magnify the image a bit more for me."<br>

It's not as simple as that, unfortunately. A magnifier is designed as a magnifier, not a correction diopter.<br>

I'm not familiar with that particular piece of Hasselblad equipment.<br>

Most camera viewfinder systems (without eyesight correction diopters) are designed on the assumption that the viewer sees well at a distance of something like 1 metre. If you do, you don't need a diopter.</p>

<p>Can you just remove the diopter?</p>

[jaydesi]

<p>The diopter corrects for vision, so it should correspond to the strength of your glasses. If it doesn't, you won't be able to see clearly. Presumably, the diopter lens has replaced the normal lens in your finder...you'll need a plain one in order to see clearly. Or wear a pair of glasses or contacts that are -1.00 stronger than your prescription (if your Rx is -2.25, wear -3.25), which is probably a more costly route, and will keep you from seeing clearly when you aren't looking through the camera.</p>

[jon_kobeck1]

If I unscrew the diopter I cant see a thing, the whole image shrinks too small. What will my optician do? Cut a

new lens for the diopter? when I use my Nikon FM2 I see the focus fine. SO maybe I should buy a neutral

diopter.

[george_carpenter1]

<p>Some of these finders were compound optical systems and the same diopter lens would be a different value, depending on which finder one was using. The moral of the story is to have access to several strengths that are made for your model and test until you get the right one. Your optician may be able to calculate what is needed on top of what you have, but the value may only be relative to that particular optical system and not be a true, or base, value. For a long time, I was severely nearsighted and purchased and tried several until I got the right one for my viewfinders. Many had different markings for different finders, e.g., 45 or 90 degree. There is, also, one of the finders that has an adjustable diopter. It is adjustable over a relatively narrow range, but adjustable nevertheless. Not only that, I think that is was for one of the 90 degree models. You might want to call Hasselblad tech support. I'd loan you mine, but they were all in the -4 and -5 category and most people are not that far out. I no longer have to use them after cataract surgery, or maybe only -1 at the most for my left eye.</p>

[jon_kobeck1]

This suks. They arent too cheap on ebay, I hate to but a bunch to test

[q.g._de_bakker]

An optician wil be able to provide a lens of the required power.<br>He/she just has to measure the lens in the eyepiece now (they have a 'machine' that will do that in a matter of seconds, with great ease), subtract 1 dioptre from the value measured, and you know what power the 'neutral' lens is. (And it certainly sounds like that is what you need).<br>If not already in stock (which is unlikely: such small diameter lenses are not everyday items for opticians) a 'blank' of the the desired power and approximate size can then be ordered (from a catalogue), and for not too much money (think $20 - 30).<br>The thing however is whether he /she is able to get the original lens out and replace it with the new one. Should be possible, but maybe not everyone is willing to give it a go. So let him/her examine the eyepiece first.

[john_stockdale2]

<p>Jon, what is your eyeglass prescription?</p>

[jon_kobeck1]

I have no idea what my prescription is, its not strong though I know that. I only wear glasses occasionally

when driving at night etc

[tom_harvey3]

<p>You could probably approximate your necessary diopter strength by trying on different strengths of reading glasses at your local pharmacy.</p>

[q.g._de_bakker]

Do remember what was mentioned before in this thread: the eyepiece is not just a correction lens (like eyeglasses are), but part of an optical system.<br>That means that markings as "+1" are relative, compared to the refractive power of the "neutral" eyepiece, which itself has a refractive power that is not "0" or "neutral".<br>So though you can find out what correction, compared to that "neutral" lens, you need by trying on reading glasses (look for ones that allow you to see well in the 2 to 3 metre range), if you want to have an optician replace the lens in the eyepiece, the power of the replacement lens needed is not just the power of the reading glasses that work best, but that of the original lens in the eyepiece, minus the +1 correction (because it is an +1 eyepiece), and plus or minus the power of those glasses.<br>If you get an original Hasselblad replacement eyepiece, you can of course select the one that coresponds with the power of the reading glasses that work best, since Hasselblad will have already taken the power of the "neutral" lens into account.

[john_stockdale2]

<p>Jon has already a +1 on his camera. He has weak eyeglasses. My guess at this stage is that he needs distance glasses, on the basis that the +1 is bad and a standard non-correcting setup probably works for him without correction. Trying reading glasses would not help, would it? I suggest he get his prescription from his optometrist or whoever made his specs.</p>

[john_stockdale2]

<p>My guess is that the standard eyepiece lens (marked 0 diopter) would be worth a try if one can be borrowed or tried in a store.</p>

<p>Reading glasses are + diopters. Since +1 is bad, 0 is probably closer to what Jon needs. Distance corrections are - diopters. It may be that a low value - diopter is optimum for him.</p>

[q.g._de_bakker]

John,<br><br>You can also get minus reading glasses. They are for people like me, who need minus glasses for distance, but quite a bit less minus, but still not plus, for reading distances. So i do have a couple of those.<br><br>I agree with your analysis, that a "0" diopter eyepiece would be a good thing to try.

[john_stockdale2]

<p>"You can also get minus reading glasses." <br>

News to me! I haven't seen them or maybe I haven't looked!<br>

Or maybe my eyes are so bad I couldn't see them!</p>

[User_4136860]

<p>Take your camera into an approved Hasselblad dealers store and they should have a set of correction lenses for you to try to select the right one for you.</p>