Question on acutal aperture size on different lens

Started Feb 10, 2008 | Discussions thread
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Zhiyong Sun
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Question on acutal aperture size on different lens
Feb 10, 2008

Another questions, as I know this forum THE resource for knowledge.

I was looking at the kit lens, the OM 50mm F1.8 lens, and the Canon pro1 lens from the front. Before this, I thought all Aperture of same F number have same actual size (so the light coming in is in same amount).

However i found the OM 50mm lens, when set a F3.5, have a much larger hole than the one on the kit lens at 14mm F3.5. Then the Canon pro1 have a even smaller hole at F3.5.

How can the actual size be so different when theoratical same amount of light is getting through?

Thanks.
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