http://www.adammillerrealtor.com/digital-slr-camera-lenses-explained/
Can someone explain slr lenses zoom with optical zooms?
looking to buy a slr camera and lenses, and want to know what the lenses compare to on a regular p&s digital camera,
thanks
A “true-to-life” (if such a thing exists) focal length on a 35mm camera is 46mm… though the actual lens focal length that is available is 50mm.
So, as far as zoom, a 2x zoom, would then be 92mm. Most manufacturers have lenses in 85mm, 90mm, or 100mm, to represent that 2x focal length.
By that estimation, I believe you could consider a 200mm lens to be 4x, and so on.
This all assumes a full-frame sensor or a 35mm camera. If you’re using a DSLR with a 24mm sensor (ie, not a pro-end camera), these ratios are actually a bit higher.
Canon DSLR kit lens upgrade group test