10D and f-stop values with 2 diff. lenses

[dschwartz69]

I posted a similar question on the lens board, but this also pertains to the body and I"m sure someone on this forum knows the answer:

Comparing two lenses, say the 50mm f/28 and the 17-40 f28L. The 50mm has a lens diameter of 2.7 in. and the 17-40 has a diameter of 3.3.

If both lenses (on the same camera body) are set to the same f-stop, say f4, will the larger diameter lens let in more light (i.e. 20% more light if diameter is 20% larger?)

Or, if my thinking is invalid, does an f-stop of f4 on specific camera body let in a set amount of light no matter the lens (this does not make sense to me.)

Can someone please enlighten me?

Thanks,

David
_______________
Canon EOS A2E
Canon EOS 10D
50mm 1.8 II
135mm 2.8 Soft Focus
28-105mm 3.5-4.6

[Keiffer]

They both or any lense for that matter will let in the same amount of light, granted if you were to look in the front of the lense one will be larger than the other but thats to make up for the length of the lense but will equal the same amount of light according to the camera.

[rent]

please don't cross post. it is annoying.

see my reply at the lens thread: http://photography-on-the.net/forum/showthread.php?t=75237

-alex