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Where To Buy Canon Lenses

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Where To Buy Canon Lenses

A variety of lenses from third-party manufacturers Sigma, Tokina, Tamron, and others are available in Canon EF mounts to fit Canon EOS camera bodies. However, contrary to popular belief, these companies are not "licensed" to produce these lenses; instead, their designers must basically take apart and analyze EOS cameras and lenses, and then "reverse-engineer" them to fit and operate on EOS camera bodies.

All Canon EF lenses have a microprocessor within the lens that provides a number of items of information to the camera. When you turn on an EOS camera film or digital the camera and lens communicate, and the camera "knows" the lens' focal length, if it's a zoom lens the actual zoom setting it's currently set to, and the maximum and minimum apertures, among other things. When the camera is activated, this basic information is transmitted to the camera body's main processor. When the autofocus and light metering are activated by pressing the shutter button halfway down, additional communication is carried out, chiefly signaling the aperture control motor within the lens to stop the diaphragm down to an amount determined by the camera (or the user, if the camera's used in Av or Manual exposure modes), and a start signal is sent to the lens' built-in focusing motor to begin driving the focusing elements of the lens for autofocus. This is only a thumbnail sketch of what occurs between body and lens. Many additional items are communicated back and forth between the time the camera is turned on and the moment the shutter button is fully depressed.

Since the first EOS cameras and EF lenses in 1987, a number of new technologies have been introduced into Canon's EOS system. As new camera and/or lens features have been developed, this has added to the amount of items communicated between body and lens. Canon has been able to do this and maintain practically total compatibility going back to the earliest EOS bodies and lenses. Most importantly, the lens mount and the gold contacts have not changed one bit! Features introduced since 1987, which have altered the way data, is communicated include:

Furthermore, as new cameras have been developed, new and faster communication methods have been introduced to give us faster autofocus, more precise light metering, faster shooting speeds (up to 9 fps with autofocus on the EOS-1v, for instance), and of course the new features that digital SLRs bring to the table. Data communication has accordingly changed over time, and occasionally a new camera will be launched that modifies how data is transmitted between body and lens. For example, when E-TTL was launched with the EOS Elan II camera in 1995, its aperture stop-down communication was altered compared to previous EOS cameras. Again, all Canon-made EF lenses had processors able to accommodate the shift in data transmission, and worked without modification.

The makers of third-party accessory lenses are not given this information when Canon introduces new features or improves the performance of its cameras and lenses. It's up to them to continue to "reverse-engineer" their equipment to enable it to continue to work on new EOS bodies as they're developed. Since Canon designs our own processors and all electronics within the body and lens, we have been able to maintain backward compatibility. This is one of the many advantages of choosing a Canon EF lens.When changes in communication result in a third-party lens that now produces errors, it's up to the makers of that lens to update the equipment to work on the EOS camera in question. Again Canon's own EF lenses work without modification.

Many third-party lenses with EF mounts are sold to customers with the claim by store salespeople or even the lens manufacturer that they're "fully compatible" with all Canon EOS cameras. Canon, Inc. in Japan and Canon USA offer no rebuttal to those claims. Any compatibility is based on the reverse engineering we described earlier in th


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