Which is better in low light? Aperture vs lens diametre

[jedipie]

Hi this may be a silly question but which of these lens will be better to use in low light conditions on a cropped body (D5000):

Nikon 35mm DX 1.8 52mm diameter or Nikon 24-70mm FX 2.8 77mm diameter?

I know that low aperture allows in more light but so should a larger filter size???

Comments most welcome! Thanks

 

[scottthehat]

a lower apature will always let in more light end of,
if a lens has a 110mm filter with a max apature of f4 and the other a 40mm with an apature of f1.4 the f1.4 will still be a better option by far.

 

[EdBray]

The physical size of the lens/front element does not have any bearing on it's speed.

The f no is a sum of the focal length divided by the size of the aperture.

Thus a 50mm lens with s 25mm aperture would give an aperture of f2 if the same focal length lens had an aperture of 50mm then it would be an f1 lens. The Canon 85L f1.2 has a relative aperture of 71mm. The Canon 200L f2 would have a relative aperture of 100mm.

Zooms are slower than primes as they have very much more complex light paths.

 

[jedipie]

thanks guys

I kinda thought that was the answer, but always best to ask the experts!

Cheers

 

[hollis_f]

The physical size of the lens/front element does not have any bearing on it's speed.

Well, except that the size of the front element tends to give some indication as the the size of the physical aperture. That's why the 400 f/2.8 has a bigger lump of glass than the 400 f/5.6

 

[EdBray]

Well, except that the size of the front element tends to give some indication as the the size of the physical aperture. That's why the 400 f/2.8 has a bigger lump of glass than the 400 f/5.6

Not really always true though, my 24-105L f4 has a bigger front element than the 85L f1.2, 135L f2, 35L f1.4, 85 f1.8, 28 f1.8, 50L f1.2, 50 f1.4, 50 f1.8, 35 f2, see a pattern here?