The 50mm is faster (ie, has a lower f number), but it does not have a bigger aperture.


f number is defined as focal length / aperture, so aperture = focal length / f number. Thus the 50mm has about 36mm aperture, the 85mm has about 47mm.


Aperture, along with death and taxes, is one of the Great Universal
Invariants. You can crop a picture and make it look like it was taken
with a longer and slower lens, but aperture always looks the same, no matter the size of your ccd.


I realize now that Gadget- who will do almost anything for aperture- might have meant f number when he said aperture. People sometimes do.