Dioptric correction on a camera is the correction of the viewfinder focusing. In simpler words, it is matching the power of your glasses (if you have one) with the viewfinder. Once you do the correct adjustment, you will be able to see things clearly through the viewfinder without using your spectacles. Sounds nice ? Well, it is equally easy as well !! It is just that many are not aware of this simple but very useful utility in almost all DSLR camera.

The procedure :

1. Set your camera on a flat surface, easy enough for you to see through the viewfinder.
2. Place an object at short focusing distance in front of the camera.
(It is good idea to use something that has fine text that you CAN NOT read without your spectacles.)
3. Use the camera AUTO FOCUS function to set exact focus on the subject.
4. Remove your glasses and see through the viewfinder.
You will see the subject unfocussed and blurry. (Depending on the power of your glasses.)
5. Now turn the DIOPTRIC correction wheel (small wheel located next to the viewfinder with and – signs on it.) till you get clear vision of the subject.

Well, that is it…. you have adjusted the camera viewfinder as if to replace your glasses while shooting !!!
Enjoy the thrill of shooting without glasses.