The other day I lent my camera to a friend and the next morning came back to find that the viewfinder picture and text was no longer clear. My immediate response? What the hell! He either broke, smudged or got my camera wet! I tried everything, though the lens looked clear, the pictures were sharp and nothing else seemed to be amiss. That’s when I realized my friend wears glasses. He had adjusted the camera’s diopter so that he wouldn’t have to wear them!
Well that’s great. But after searching for 20 minutes through the camera’s menu and settings- I couldn’t for the life of me reset the diopter! I hope that this post helps you understand how and why you would need to adjust your camera’s diopter.
Short answer:
Check for a small dial near your viewfinder housing (i.e. the little hole you stick your eye in to see what you’re about to photograph). Turning the dial shifts the focus from near to far and can correct for near/farsightedness. Now you won’t need to smash your glasses up against the camera!
To properly set your diopter, place your camera on a tripod or other stable surface and focus (by pressing the shutter release down halfway) on something flat. Without moving the camera turn the diopter dial until the viewfinder image is clear- to YOUR eyes. This setting can essentially replace your eyeglasses by automatically compensating for your visual acuity (or lack thereof!).
Long answer:
I found this article to be very helpful in understanding how diopter adjustment works: Using Diopter Adjustment.
Hope this helps!