08-07-2010, 07:25 AM
The Tamron 28-75 is a fullframe lens. As such it can be used on Aps-C, too, without any problems apart from the changed field of view because the image circle of the lens, is far bigger than the aps-c sensor.
Third party manufacturer do in fact differntiate between Aps-c and full frame lenses. They usally use differnt letter codings in the lens names to identify for which sensor size a lens was made. APs-C lenses have a smaller image circle which results in black corners when mounted on fullframe.This is why it does not make sense to use Aps-c lenses on full frame. (In case of Canon aps-c lenses (called EF-S) it isnt even possible to physically mount an aps-c lens on a fullframe body, because of the mount. Canon full frame lenses can be mounted on aps-c cameras however.)
Unlike Canon themselves, third party lensesmaker do not use the EF-S mount for APS-C lenses. This is why their Aps-C lenses can be physically mounted on full frame cameras, without damaging the mirror. If done so, Aps-C lenses do deliver black corners, however, because their image circle is not sufficient for full frame.
Third party manufacturer do in fact differntiate between Aps-c and full frame lenses. They usally use differnt letter codings in the lens names to identify for which sensor size a lens was made. APs-C lenses have a smaller image circle which results in black corners when mounted on fullframe.This is why it does not make sense to use Aps-c lenses on full frame. (In case of Canon aps-c lenses (called EF-S) it isnt even possible to physically mount an aps-c lens on a fullframe body, because of the mount. Canon full frame lenses can be mounted on aps-c cameras however.)
Unlike Canon themselves, third party lensesmaker do not use the EF-S mount for APS-C lenses. This is why their Aps-C lenses can be physically mounted on full frame cameras, without damaging the mirror. If done so, Aps-C lenses do deliver black corners, however, because their image circle is not sufficient for full frame.