Digital Cameras and Focal Length

  Spock1958 12:00 08 Apr 2005

I have been reading up on the Canon EOS20D, and one thing I noticed was that because of the way these cameras are made, one needs to multply the focal length of a lens by 1.6 therefore a 50mm lens effectively becomes a 80mm lens.

Does this mean that if I put a 50mm lens on the camera, it effectively becomes a telephoto, or:

Does it mean that 80mm is now a standard lens for the camera.

Can somebody explain the theory behind this multipication factor?

  Charence 12:45 08 Apr 2005

click here for some info.

There's a multiplication factor because the lens is 50mm when the size of sensor is 35mm, however, on most dSLRs such as the 20D, the sensor size is smaller than 35mm which means creates a multiplication factor.

  Stuartli 13:03 08 Apr 2005

Not quite true. A digital camera sensor is smaller than the 35mm equivalent, therefore using a 35mm camera lens would mean that a smaller proportion/area of the lens's image would be recorded on a digital camera's sensor (it gives the impression of being a telephoto lens because, of course, it has a longer focal length).

Therefore digital cameras use shorter focal lengths for single or zoom equivalents - to make it easier to reconcile with 35mm cameras, manufacturers indicate the coverage that would be provided with a film camera lens and body i.e 35-105mm or 28-200mm zoom and so on.

One or two of the latest (expensive) digital cameras have sensors that are the same size as that of a 35mm camera, thus enabling these lenses to continue to be used and save the cost of buying replacements.

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