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11 questions
Newest Active Bountied Unanswered
0 votes
4 answers
96 views

Brightness of a full frame lens mounted on aps-c vs mounting an identical native aps-c lens [duplicate]

I am a bit confused about the effect of using a full-frame lens on a aps-c camera on the brightness of the resulting image. Lets say we have two lenses: A full frame 50mm f2 lens An aps-c 50mm f2 ...
Leander Moesinger's user avatar
Leander Moesinger
  • 103
8 votes
6 answers
2k views

Does a lens with a bigger max. aperture focus faster than a lens with a smaller max. aperture?

The assertion by a well known photographer is that the Nikon 400mm f/2.8 set to an aperture of f/5.6 will let in 4 times the light compared to a Nikon 500mm f/5.6 lens set to f/5.6, keeping the ...
Michael Davis's user avatar
Michael Davis
  • 193
0 votes
2 answers
66 views

How do constant aperture zooms produce identical exposure, even though focal length is larger? [duplicate]

My understanding is that a larger focal length corresponds to a larger working aperture diameter, since the numerator is larger. Why doesn't a larger working diameter correspond to a brighter image? ...
neaumusic's user avatar
neaumusic
  • 113
4 votes
3 answers
3k views

Which formula for f-numbers is correct: f/D or 1/(2NA)?

I've seen two different definitions for the f-number of a general-purpose lens. Are they consistent ? I'm assuming that subjects are distant (not macro, magnification is small), and we have a lens ...
JEJV's user avatar
JEJV
  • 41
2 votes
5 answers
2k views

Does a full frame lens require more light on a crop body? [duplicate]

When using a full frame lens on a crop body, does the lens require more light? If I use an f/2.8 full frame lens on a crop body, does it become an f/4.2 (*1.5)?
Moon's user avatar
Moon
  • 145
6 votes
2 answers
1k views

How does sensor size affect the brightness of an image given the same field of view and aperture?

Lets say we have two image sensors, each one with 1MPixel resolution but differing in size. The first sensor has the size 1/3", the other one 1". Each sensor is equipped with a suitable lens (for the ...
Echo88's user avatar
Echo88
  • 153
2 votes
2 answers
5k views

Will a faster lens, like f/1.4, help get better Milky Way images?

I have a Nikon D7000 and don't know whether my 50mm 1.4 or 17-55m 2.8 lens would be better. I was automatically going to go with the 50mm lens, but then I was reading up on how I can use a longer ...
thegaffney's user avatar
thegaffney
  • 123
0 votes
1 answer
996 views

Nikon Lens - Stopping down causes over exposure in Aperture Priority mode

I just got a used Nikon 300mm f/4 AF (the older, non-AF-S version), and unmounted, when set to f/4, the aperture blades are still slightly visible (you can push the aperture lever on the lens a bit to ...
Brian's user avatar
Brian
  • 41
23 votes
5 answers
4k views

Why do two lenses with the same F-number give different amount of light?

Why do the following two lenses provide different amount of light? In both images we have fixed focusing distance, distance to the object, ISO, shutter speed and F-number.
Sunny Reborn Pony's user avatar
Sunny Reborn Pony
  • 559
32 votes
2 answers
27k views

What is T-number / T-stop?

Usually, when discussing aperture of a lens, F-stop and F-number are used for quantifying. But some photographers, and especially videographers, also mention T-stop. The concept and numbering used (e....
Imre's user avatar
Imre
  • 32k
3 votes
4 answers
747 views

Why does my camera's meter suggest the same exposure time for lenses with different apertures?

On the same camera body (Canon 1Ds MkII) at the same ISO setting (400) and with no filters attached, two different lenses give the same exposure time (0.4s) at very different apertures. The lenses and ...
John Thomas's user avatar
John Thomas
  • 4,495