DioptersWhat is a Diopter? The technical definition is “A unit of measurement of the refractive power of lenses equal to the reciprocal of the focal length measured in meters”. The term diopter is used mainly in optometry, as a term for a corrective lens. It is also sometimes used as a measurement of curvature, and in the relation to magnifying power. But what is a diopter when we talk about them in photography? The term can refer to two different things, but for either application, it is essentially a piece of glass used in focusing. The most common diopter on a camera is part of the eyepiece on a viewfinder of a camera that adjusts the focus based on the users eyesight. The other type of a diopter in photography is also sometimes referred to as a close up lens, which is something that allows you to focus at a closer distance, almost like a macro lens. For the purposes of this article, we will be talking about the diopters used in conjunction with viewfinders.
|Variable diopter adjustment by wheel|
|Variable diopter adjustment by slider|
|Eyepiece that requires a slide-on diopter (rectangular)|
|L- A threaded screw-on diopter, R- a slide-on diopter|
|A -1.5 (standard) diopter on a Mamiya RZ waistlevel|