Digital SLR zoom lenses

could you tell me if there is a ratio between the focal length of a lens and magnification. thanks

Hi

For 35 film cameras, you get 1x for each 50-55mm of focal length. In other words, a 300mm lens is basically a 6x. In digital, after the pic has been processed, depending on the camera, there is also an enlargement factor of about 1.5x, though this will vary and should not be taken too literally. A 300mm lens on a digital SLR get you a pic with a bit more enlargement after you take the pic, say 8x or 9x. The lens is still a 300mm lens, optically, though. That does not change.