What is Diopter?
Diopter is often referred as power unit of lenses. A lens with a focal length of “1” meter is called «diopter». In ophthalmology, myopia and hypermetropia are expressed by diopter. The power of a lens is inversely proportional to its focal length.
Normally, focal length of a lens takes values such as 50 mm, 100 mm in terms of millimeters in cameras. Power of a lens, dioptre, is defined as follows:
Diopter = 1000 / lens focal length
That is, diopter of lens is obtained by dividing the focal length of a lens by 1000. For example, the diopter of a 50 mm lens is 1000/50 = 20 and is expressed as +20.
How to Adjust Your Camera Diopter to Your Eyesight
Everyone unfortunately could not see with the same sharpness and clarity due to eyesight problems and photographing with glasses can sometimes be a complete torture. If you have visual defects such as astigmatism or myopia at a higher levels and you look through your camera’s viewfinder without glasses, you will have a blurry vision.
Question: How do I calibrate the diopter correction on my DSLR’s viewfinder?
Easy. To get rid of this problem, you can adjust use diopter adjustment on your camera. The diopter is placed next to the viewfinder in your DSLR camera. What you need to do is simply to look through the viewfinder with the camera turned on and then proceed to + or – directions until your eyesight is clear and sharp. When you get the best vision, you need to lock diopter key / button in that position or value.
Congratulations. Now you can take pictures without glasses.
See how to use diopter adjustment on your camera: