Focal Length and Sensor Size
The focal length of lenses is calculated based on the diagonal measurement of a frame of film. In many digital cameras, the sensor is often smaller than a traditional film frame, which is why the focal length of a lens needs to be recalculated for a
digital camera. Depending on the sensor size, a general rule would be to multiply the lens size by 1.6. For instance, a 35mm lens would actually be equivalent of 56mm on a digital SLR like the EOS 350D.
Next month, we look at using a flash.