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158 reputation
7
bio website andyc.ac
location United Kingdom
age 34
visits member for 2 years, 11 months
seen Sep 25 '13 at 11:28

Software engineer in Manchester, primarily working on C control systems.


Sep
25
awarded  Popular Question
Mar
29
awarded  Caucus
Jan
16
awarded  Scholar
Jan
16
accepted Is overall light gathering of a lens only dependant on aperture?
Jan
15
awarded  Nice Question
Jan
13
comment Is overall light gathering of a lens only dependant on aperture?
Oh yeah! Think things are making sense now.
Jan
13
comment Is overall light gathering of a lens only dependant on aperture?
I think I've got it. Essentially for a F/0.95 50mm lens, the effective diameter has to be 52.6mm. That isn't particularly enormous, but to be that size, the lens would have to be able to focus light hitting the very edge of the lens back to the correct point of the sensor. Generally cheap lenses will not be able to achieve this, so even though the cheap lens may be 52.6mm or bigger, only light hitting fairly close to the centre can actually be used for a focused image - if you dismantled it to remove the aperture blades, you would get more light in, but not focused to an image.
Jan
13
comment Is overall light gathering of a lens only dependant on aperture?
I understand the physical idea of stopping down a lens. Just because you've got a large lens doesn't mean you have to use it wide open. The bit I'm confused about is that the large aperture lenses don't seem to need to be as much bigger compared to the smaller aperture ones as I would expect.
Jan
13
comment Is overall light gathering of a lens only dependant on aperture?
That does make sense but I still have some doubts. E.g. 50mm F2.8 here amazon.co.uk/exec/obidos/ASIN/B000GT11FI/watersphotogr-21/… versus 50mm F0.95 here noktor.com/products.php - by this formula, the numbers should be 52.6mm and 17.9mm, and the lenses don't look that far different.
Jan
13
awarded  Student
Jan
13
awarded  Supporter
Jan
13
comment Is overall light gathering of a lens only dependant on aperture?
Just had a good look through that and I'm still left a bit confused! Does the aperture relate in some way to the diameter of the lens?
Jan
13
asked Is overall light gathering of a lens only dependant on aperture?
Jan
13
awarded  Autobiographer