I'm coming in late to your conversation here - found it on search, and am TOTALLY getting a replacement magnifying eyepiece ASAP (astigmatic and over -4 here in both eyes, with old age presbyopia setting in too.) Thank you so much, I had no idea such a product existed. I struggle with focus in manual mode because I've never been able to compensate properly, my glasses slip around when I am peering down the barrel like that.
Originally posted by ChopperCharles 
The question i have is why doesn't the stock diopter work in both directions? Why only correct for one type of vision problem and not another?
The reason for only offering one kind of correction isn't a fault of Pentax, it's a law of physics. Different kinds of lenses correct near vs. far. It's not really perceptible anymore in modern eyewear, it used to be more apparent when looking at someone in + vision glasses, that correcting farsightedness was a matter of magnification (they looked a bit bug-eyed) which uses convex lenses - and people with strong myopia looked like they had tiny eyes (in the coke-bottle glasses era.) That uses concave lenses. Having both present would make for a very long diopter slide, to accommodate everybody.
My daughter is a more than a -9 in both eyes, with a +2.5 added in (and she isn't quite 21, poor kid - totally night blind too, but she's graduating from a tough college shortly, so it hasn't held her back any!) Her modern glasses are hardly different at first glance from anyone else's - you can only see the distortion around the edges (her eyes look normal straight on through the middles.) It does mean she doesn't have much peripheral vision in them, though. It's very difficult for her to use viewfinder optical devices, like an eyecup camera or a microscope. Cameras with LCD view are a blessing in her case. (Her photography interest isn't much beyond carrying around her Optio point and shoot for snapshots though, so no loss there.)
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