I am getting old people eyes and have noticing that my shots are becoming less and less successful-- as in less sharp. Several months ago I fiddled with the diopter while sitting in a car [this is how little I know] waiting as my husband put gas in it. Hey I adjusted until it seemed clear through the viewfinder. I must have got it right because my success ratio wasn't bad, the fails I attributed to shaky hands or whatever seemed reasonable. But it's gotten worse and I just figured my eyes are too bad for the camera. Anyway I go to the camera store today and am testing a lens on my camera, a manual zeiss lens, and I can't pull off one clear shot and mention it to the sales person. He asks me if my diopter is adjusted and then he tells me how to do it more properly. Set the camera on a tripod and using autofocus, set your focus, then adjust your diopter without bumping the camera, until you see clearly. Maybe because it is overcast and even occasionally drizzling out I am not seeming to get good results yet. Do I need high contrasts to get it just right? Focused on the neighbors garage across the street, on bird cage bars, on the truck headlamp.. even changed lenses. I'm missing something or I need to give up this hobby due to eyesight Camera is my Canon XSi, lens currently on it is the 28mm 1.8, I also have an eyecup extender on the back, the EP-EX15. My first adjustments were made with the eyecup off, the second time I put it on and used the tip of a toothpick to turn the diopter wheel. LCD reviews look bad so on the computer I don't expect pixel peeping to help. I'm seriously about ready to sell it ALL. Help?