Article about photographic lenses and equipment

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Flange Focal Distance of Photographic Lenses and Cameras

At times there can arise a need to use lenses from one system with another. The most prominent example is the use of old lenses with modern SLR or mirrorless (Evil) cameras. This combination will work only under the following condition: the flange distance of the lens must match the flange distance of the camera.

So we decided to try out some old manual lenses in action. Usually you can attach these lenses using adapters. But not all of old lenses can be easily installed to any modern camera. The primary reason for this is one of the key parameters of a lens, the flange focal distance (FFD).

The flange focal distance of a lens (or camera) is the distance between the lens mount and the focal plane (the plane of the film or camera sensor).

Flange focal distance is measured in millimeters. As such, taking for example the popular Canon EF, its flange focal distance is 44mm.

What is this important for us? It's simple. If the lens FFD is longer than the camera FFD (at least 1 mm, the minimum thickness of an adapter), it can generally be used with the given camera through an adapter without any restrictions, meaning that it will be able to focus to infinity.

If the flange focal distance of a lens is shorter than the camera’s FFD, then you'll need a substantial modification of the lens shank, or you must use an adapter with a compensating lens, which immediately negatively affects image quality. You can, of course, just use such a lens for short distance and in close-up work only though.

There is a structural problem in some SLR cameras (especially the Canon 5d and Canon 5d mark II). The lens may be suitable for the camera by FFD, but due to the camera’s design, the mirror will come in contact with the shank of the lens (usually this problem can be solved by either filing a few millimeters off the shank or disassembling the shank).

Here is a table of flange focal distances for modern and older systems. They are sorted by FFD value.

Table 1. Flange focal distance of modern photographic lenses and cameras

Table 2. Flange focal distance of older photographic lenses and cameras

Here’s what we can take away from the above data:

Useful links:

The most complete table of Flange focal distances on different systems

(с) 2010 Sergei Borodin

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