Serene Life

by garik

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137 reputation
6
bio website
location United Kingdom
age
visits member for 1 year, 11 months
seen Apr 10 at 22:22

Oct
24
awarded  Teacher
Oct
24
answered Why do two lenses with the same F-number give different amount of light?
Oct
23
accepted Size of the entrance pupil vs size of the aperture
Oct
23
accepted Help me understand effective f-number
Oct
23
comment Help me understand effective f-number
Thank you, that is very clear! That also explains why I did the test myself and couldn't see much difference between infinity and closer focus (I am not using a macro lens). The numerical example was very useful too!
Oct
23
comment Help me understand effective f-number
@mattdm Questions could be related but I don't see it as a duplicate
Oct
23
comment Help me understand effective f-number
@MattGrum That is my point (I just call it 'effective f-number' instead of 'effective f-stop').
Oct
23
comment Help me understand effective f-number
Sure, mine is more a theoretical curiosity rather than a practical consideration
Oct
23
comment Help me understand effective f-number
@RussellMcMahon The f-number you are referring to is still the infinity f-number.
Oct
23
comment Help me understand effective f-number
Thanks. In other words you are saying that no matter at what distance you are working at, a lens will collect the same amount of light when set to a certain f-number. I then wonder why the concept of effective f-number has been introduced.
Oct
23
comment Help me understand effective f-number
@JamesSnell Hope it's more clear now
Oct
23
revised Help me understand effective f-number
added 30 characters in body
Oct
23
asked Help me understand effective f-number
Oct
17
awarded  Commentator
Oct
17
awarded  Student
Oct
16
comment Size of the entrance pupil vs size of the aperture
I was under the impression that the f-number was defined as the ratio of focal length and aperture, and that the entrance pupil was just the apparent size of the aperture. I tend not to necessary trust wikipedia. Here for example (en.wikipedia.org/wiki/Aperture) the f-number is specified as a ratio of "focal length to effective aperture diameter".
Oct
16
asked Size of the entrance pupil vs size of the aperture
Oct
15
awarded  Scholar
Oct
15
accepted Can I estimate the light gathering power of a lens by measuring size of entrance pupil?
Oct
15
comment Can I estimate the light gathering power of a lens by measuring size of entrance pupil?
I'm sort of convinced now, thank you!