What Is Dioptre Adjustment?


I just got spectacles and was told to use Dioptre Adjustment to adjust the focus on my DSLR. Can you tell me how this change can be made?
Jai Krishnan, via email

This article was originally published in December 2014.

The glass elements of the viewfinder are made to allow your eye to focus on a ground glass focusing screen within the camera. If you wear glasses, you may find that they obstruct your view when you look through the viewfinder of your camera. If you use prescription spectacles with a number, you will find it difficult to focus on the image in the camera viewfinder without your glasses on. This is especially true if you are hypermetropic or long-sighted.

This is where your camera’s ‘dioptre adjustment’ or ‘dioptre correction’ can help. It is a small dial or knob placed usually above or below the viewfinder, and has ‘plus’ and ‘minus’ symbols on it. It helps by mimicking the dioptre number of your spectacles, adjusting the focus of the viewfinder on the internal focusing screen, so that you don’t need your prescription glasses when you shoot.


How is it Useful
Since everyone’s eyes—and any prescriptions that go with them—tend to be a little different, it can be adjusted to compensate. This is especially useful if you wear bifocal or trifocal spectacles.

However, it cannot compensate for all vision problems, as it has a limited range of dioptre corrections; for instance, from -3 to +3. Dioptre adjustment is also often found in binoculars, telescopes and microscopes.

How Does it Work
To adjust your camera’s dioptre adjustment, place your finger on the dioptre correction dial and look through the viewfinder.

Next, move the dial as you look through the viewfinder. When the image is perfectly sharp, you can stop adjusting the dial. If the dioptre adjustment is incorrect for your exact eye and you are using the manual focus, it could lead to out-of-focus pictures, even though you can see it in focus through the viewfinder.

So make sure you use autofocus, look through the viewfinder and adjust the adjustment setting till it is in focus. As soon as the two are in sync, you can switch to manual focus if you want to.

Tags: better photography, Question of the Day, focus, viewfinder, January, 2009, Dioptre Adjustment