Canon® EOS Digital Photography Photo Workshop

2.5. EXPLORING DIFFERENT IMAGE SENSOR SIZES

In the world of digital imaging, you constantly hear or read the term "full-frame sensor." What exactly does this mean and what are the advantages and disadvantages?

A full-frame sensor is designed to capture the full size of the film frame. In the case of Canon, this is 36 × 24 mm, or the full size of the 35mm film format. The chief reason that all dSLR sensors are not full frame has to do with the cost of manufacturing the larger sensors combined with the physical size of the camera body and its ability to accommodate a chip that large. As chip sizes get larger, the yield gets drastically lower and, subsequently, the price increases. The semiconductor industry's advances in affordability have been driven by the ability to make circuits smaller and smaller, but an imaging chip must remain large, and such large chips get cheaper much more slowly. Owning its own chip-making facility has made Canon a leader in full-frame sensor technology.

Consider several of the more popular sensor sizes and the cameras that use them:

• APS-C sensor. This is named for the now-all-but-defunct film format introduced and popularized by Kodak. This is the sensor size used in the Canon EOS Digital Rebels, the EOS 30D, and the EOS 40D. This smaller size results in what is known as a crop factor. In the case of Canon, this is 1.6x, meaning a 100mm lens now has the effective focal length of 160mm, a 200mm lens has the effective focal length of 320mm, and so forth. ...