mmm...fengwei's description on magnification got me wondering too.
As an astronomers, magnification on a telescope is obtained by dividing the focal length of the main objective (main lens) by the focal length of the eyepiece. for the same focal length, you get the same relative sized image on any telescope , everything else remaining the same. For cameras, they are quite so different. I know magnification of a zoom lens is the maximum divided by the minimum focal length. that's how 18-250 yields x13 or a 70-300 yields x4. But the image size can be entirely different for different x4 lenses. And I wonder how you calculate for prime lenses since there is nothing to divide! :think: Its all so confusing...!
As an astronomers, magnification on a telescope is obtained by dividing the focal length of the main objective (main lens) by the focal length of the eyepiece. for the same focal length, you get the same relative sized image on any telescope , everything else remaining the same. For cameras, they are quite so different. I know magnification of a zoom lens is the maximum divided by the minimum focal length. that's how 18-250 yields x13 or a 70-300 yields x4. But the image size can be entirely different for different x4 lenses. And I wonder how you calculate for prime lenses since there is nothing to divide! :think: Its all so confusing...!