Posted to Digital SLR Articles 2009-03-14
How many different mounts are there?
Since film SLR cameras became popular in the late 1950's, each manufacturer has used different adapters to mount lenses to the camera bodies. Most often the lens mount differences are found between manufacturers, though cameras and lenses of past eras will sometimes have variances with those currently manufactured by the same company. The mountings also differ depending on features such as auto-focus.
There are several different types of mountings commonly seen on 35mm and DSLR lenses.
• The F-Mount used by Nikon
• The Minolta AF Mount, now proprietary to Sony
• The M39 Mount used by Lecia and Contax
• The M42 System used by Lecia, Cannon, Pentax and Nikon
• The Canon EF and EF-S Mount
• The Pentax K Mount
• The Sony α Mount, a descendant of the Minolta AF
These mounts are usually used for digital cameras as well as film SLRs. Though a film SLR lens may mount on a digital camera, remember that differences in the focal length may cause oddities in the picture, such as vignetting and distortions at the edges of the frame.
There is a mount called the Four Thirds System which is designed to provide interoperability between different cameras. This mounting system exists exclusively for DSLR cameras. Several third-party lens manufacturers make lenses with this mount, allowing owners to use their lenses on different manufacturer's cameras.
In general, the different mounting methods are completely incompatible with one another as they are manufacturer-specific. The Four Thirds System is the only exception to this rule. Some manufacturers however, deliberately made their DSLRs so that professional photographers could use their existing lenses. Buying entirely new lenses would constitute a very large investment for many pros.
If your lens has autofocus capability, those capabilities will only function on a mounting system that provides power to the lens itself. On older cameras, for instance, it may be possible to mount a new lens, but the advanced features will be absent.
The accusation is sometimes raised that these different mounting systems are designed so that a consumer may only use one manufacturer's products. In reality, there are many more differences between the cameras that make cross-usability more difficult than using a universal mount. Each manufacturer's cameras have subtle differences in vital aspects such as the distance between the lens and the media on which the image is recorded- film or a DSLR's imaging technology- which would render other lenses incompatible, even if they could be affixed to the camera.
Other devices that fit between the camera body and the lens also have manufacturer-specific mounting devices. Mounting hardware does produce slight differences in images, but it is mostly a personal choice.
• Some DSLRs to consider are:
Canon EOS Rebel XSi
12.2 mega pixel, 3.5 fps, 3.0 inch LCD Screen
Nikon D90
12.3 mega pixel, 4.5 frames per second, ISO 200 to 3200, 3 inch LCD screen
Sony DSLR A700
12.2 mega pixels, 3.0 inch LCD screen, approx. 5 fps
