How to pick diopters? (Mamiya 6)

[sfcole]

<p>I think I may need an diopter for my Mamiya 6, but I'm not sure. It could be my eyes, or it could just be distortion. The central spot looks a little funky. I generally use contacts, but probably need an eye exam. My eyesight currently is good, though.<br>

B&H has them for $19.99, but how does one pick the appropriate one? Should I just pick a couple, like a +1 and -1, and return the one that doesn't work?</p>

[raymond___k_osmotherly]

<p>See your optometrist. Mine advised me of my requirements based on my most recent eye-test.<br>

Ray</p>

[stwrtertbsratbs5]

<p>I wear glasses when I shoot. A diopter would make it possible for me to shoot without them, but then I wouldn't be able to read the controls on my camera.</p>

[jim_momary]

<p>Scott -</p>

<p>From a guy who has worn glasses since age 6, if you can't see you can't see. Simply put, your vision isn't corrected if something is blurry. Be it astigmatism, or a shift in prescription or the start of a cataract ... please do have it looked after. (I'm in the cataract boat as I type this and need to have it surgically redone). You cannot put a value on eyesight, it is tuly pricelss. Take care of them baby ____s (insert color here).</p>

<p>For diopters, you can pick that off your prescription. If you are nearsighted you need ' - ' correction, farsighted needs ' + ' correction. How much depends on your eye. (for discussion, nearsighted means you see well at close distances but far distance is blurry)</p>

<p>Also, most viewfinders put the apparent distance to the focus screen at something about 1 meter (if memory serves me). Try looking one-eyed at some target at about that distance, is it clear/readable? Simple test, but you may see some left/right issues.</p>

<p>Blurry & Fuzzy Jim</p>

[galileo42]

<p>Contacts? Then you are near-sighted, right? Thus you need a «-» diopter correction. But make sure you don't suffer from astigmatism as well. Then, no diopter correction will help. Been there, done that, got the diopter correctors anyway :) Helps my far-sightedness, not the strong astigmatism in my - of all my eyes - right eye. But it was nice on my now parted Mamiya 7II.</p>

[mikeseb]

<p>In optical terms, <b>nearsighted</b> means that you can see objects closeup fairly well, but have difficulty with stuff far away. <b>Farsighted</b> means just the opposite. Nearsightedness results either from an eyeball that is slightly too long front to back, or a cornea or (less frequently) lens that is slightly too convex, so that the focus plane is slightly in front of the retina. Farsightedness, again just the opposite: the eyeball is too "short", or the cornea/lens not convex enough, and the focus plane is "behind" the retina. Makes sense, then, that nearsightedness is corrected by neutralizing some of the excessive refractive power of the cornea/lens with a "negative" or concave lens, while farsightness needs additional refractive power conferred by a "positive" or convex lens.</p>

<p>The <b>cornea</b> (the transparent bulge in front of the eye) is the primary refractive surface of the eye--it does most of the work of getting an image in focus. The lens is for finer adjustments.</p>

<p>Both of these conditions are distinguished from <b>presbyopia</b> (literally, <i>old vision</i>), which is an age-related loss of flexibility (if only increased stiffness affected <i>everything</i> as one ages! :) ) of the lens, so that when one tries to read something close, the lens cannot flex enough to refract the rays into focus.</p>

[galileo42]

<p>So, okay, what I suffer from is - sigh - presbyopia. I thought I could pretend this was NOT age-related :) Now, here are the figures which could be a starting point for some: when I buy those cheap reading glasses hanging from the display at the drugstore (the ones meant to be tossed around, shoved in my jeans pocket, forgotten, broken and finally lost, not like the very expensives ones I buy from my optometrist) I take a +3 prescription. The best diopter corrector (on my F3, FM2, even my M8...) so far has been +1. It gives you an idea.</p>