Photographers choose between an APS-C and APS lens based on the picture they are taking.
Many photographers use multiple camera bodies and lenses during photo shoots. A photographer chooses a lens based on the picture they are taking. Many photographers use APS-C and APS lenses interchangeably during a day's shoot. Each lens type gives them a slightly different focal length and distance, allowing them to take pictures in different ways.
Full Frame - APS lens
The APS lens is designed for a "full frame" camera body. A full frame camera, such as the Canon EOS 5D mark 2, has a 36 mm by 24 mm sensor that is equivalent to a full 35 mm film size. APS lenses are compatible with all EOS camera bodies from full frame to crop frame sensors. The lens has a 1.6 magnification on a cropped body sensor instead of being a true 1 to 1 ratio. The lenses are commonly referred to as Canon's EF lenses.
Cropped Frame - APS-C lens
The APS-C lens was designed specifically for digital SLR cameras with a cropped sensor. Cameras, such as the Canon EOS 60D or Canon EOS 7D, have a sensor that is 22 mm by 15 mm. The APS-C lens was developed to take into account the smaller sensor and sit into the body of the camera a little more to accommodate the smaller mirror. The lenses are commonly referred to as Canon's EF-S lenses. The "S" sands for the "shorter" back focus that cropped body cameras have.
Physical Differences
Canon's EF lenses are designated with a red dot. The red dot helps to align with the camera body's red dot when mounting the lens. All of Canon's professional lenses -- or "L" lenses -- are red dot lenses. The "L" lenses are also marked by a red line circling around the lens. Canon's EF-S lenses are marked with a white square on the lens. The white square helps to show the different mounting and that it is only compatible with cropped body cameras.
Use
The APS and APS-C lenses are used in exactly the same manner on the camera bodies. They both have a focus ring and zoom ring if they are zoom lenses. The manual focus and auto focus controls are located on the same side on all lenses. The biggest difference is the shooting distances required between the two. The APS-C lens can not be used on a full frame camera because the body doesn't have the mounting required to accept the white square mount. Cropped body cameras can use both, but the difference is the 1.6 times magnification that is applied to both lenses.
Tags: APS-C lens, body cameras, camera bodies, cropped body, frame camera