# How does magnification work in lensless optical setups?

In my optics classes, I have only ever seen magnification defined in conjunction with the thin lens equation.

However, in a lensless optical setup such as lensfree in-line holography, how does one understand the principle of magnification? I have seen both equations that define magnification in the setup below as:

M = Z2 / (Z1 + Z2)

or

M = Z2 / Z1

Which is correct? Also, what is the intuition behind this magnification?

Note that the formulas in the OP give the same magnification the limit of small $Z2$.