hi, i bought a set of extention tubes for my macro work.
i need someone who can to explain to me how to calulate the new MFD and magnification.
for example when i put a 25mm extention tube on my 90mm macro that has 29cm MFD and 1:1 magnification... what is the new MFD and magnification?
or what if i put a 31mm extention tube on my 70-200mm f4.
is there maybe a good website that explains how to calculate this?