Before, lenses rating such as 18mm is considered already as a fisf eye lens. But now in the digital camera such as the default lens of Canon Rebel XT, the 18 to 55MM is just like a 28 to 90 mm of the AF lens series. It has to do with the size of the sensor. On a 35mm film camera, of course that is a certain size (24mmx36mm I think). But digital cameras do not have to be built to the same geometry; to make the cameras more compact they use a smaller image sensor and place it closer to the lens. Then they have to shorten the focal length accordingly.
This effect is not just seen in digital cameras. If you look at medium or large format film cameras you will notice they have very, very long focal lengths compared to 35mm. Happy to help! :-) Report It
Digital camera bodies have a slightly different element than film bodies. The sensor that captures the light has a magnification built in - I can't remember the specifics but I think it's like a 1.2 conversion. Hope this helps. | 