From
http://www.steves-digicams.com/cameras_digpro.html
what is the "Focal Length Multiplier" for each brand?
thanks.

Multiply the number by the focal length of the lens. A 50mm lens will act like a 65mm lens on a camera with a 1.3 multiplier. This is because the sensor on that camera is 30 percent smaller than the standard 35mm film size.

Because of the smaller format of DSLRs, telephoto lenses have a narrower angle of view than the same lens on a 35mm camera – this is the so called ‘crop’. Angle of View is simply that viewing angle which fills the frame (of any format). This determined by the film format in relation to the focal length of the lens – not the focal length on its own.



The image circle created by a 35mm format lens is shown.
The blue rectangle shows what a 35mm film, or a full-frame digital SLR will record.
The inner red frame shows what a digital SLR with a 1.6X magnification factor will record

1). 35mm Film or Full frame DSLR


2). Normal non-DSLR with 1.5x or 1.6x factor (multiplier)

简单的示意图: