Capt Donkey Smile wrote:

Hello,

Please correct me where I am wrong.

I understand that the focal length of the lens can be varied and in
doing so you change the "zoom" of the lens.

I understand that 50mm sees things pretty much as I see it. I have a
1.6x crop so to see things through the camera as I see it, I 'd shoot
at 50/1.6= ~30mm.

If I wanted 10x zoom, would I be looking for an effective focal length
of 500mm?

Thanks

You are basically correct in the first part of your statement.
Certainly not all lenses can zoom, or change their focal length.

The statement 10X zoom is ambiguous. In MOST cases it merely means the
ratio of the longest focal length to the shortest. A 30 - 90 mm lens is
a 3X zoom. It says nothing about how the telephoto focal length compares
to a standard 50mm (film equivalent).

There is no well defined term for what you are looking for, but it is
frequently called power or magnification. That is, a 100 mm lens may be
said to have a power or magnification of 2. This is NOT, however, the
same thing as the term 'magnification' used in lens design or camera
design. Since most folks (except those using macro lenses or
supplemental lenses) don't need to use the real, technical magnification
I won't say anything more about that term.