How much of a difference in low-light situations do these apertures have

Discussion in 'Digital Photography' started by covertsurfer, Apr 15, 2011.

  1. covertsurfer macrumors 6502a

    Jan 18, 2007
    I have an old digital camera and its aperture ranges from:

    F2.8 - F5.2

    The new camera I am looking at although overall a much better camera has a aperture range from

    F3.1 - F5.9

    In low-light conditions will I notice any difference between 2.8 and 3.1. Also to note is my old camera only goes up to 400 ISO wheras my new one goes to 3200

  2. miles01110 macrumors Core


    Jul 24, 2006
    The Ivory Tower (I'm not coming down)
    Since you don't mention a lens you're probably talking about some kind of point-and-shoot camera, on which it won't make much of a difference. Of course since you are only mentioning generalities it's hard to say for sure.
  3. covertsurfer thread starter macrumors 6502a

    Jan 18, 2007
  4. AnimaLeo macrumors 6502

    Sep 2, 2009
    Using your old camera stop down the aperture from F2.8 to F3.1 and you can see for yourself how much of a difference there is.
  5. covertsurfer thread starter macrumors 6502a

    Jan 18, 2007
  6. steveash macrumors 6502


    Aug 7, 2008
    This is just under half a stop so the equivalent of using iso 150 rather than 100 or 1/75 second shutter rather than 1/100. In other words there will be a difference but nothing considerable. Other features such as anti-shake/image stabilisation will make a bigger difference to low light photos.
  7. jabbott macrumors 6502

    Nov 23, 2009
    Warning: math ahead :eek:

    The area of an aperture is defined by the following formula:

    pi * (focal_length / f_number / 2)^2​

    To compare how much more light enters an aperture compared to another aperture, regardless of focal length, the following ratio can be used:
    (pi * (2 / f_number_1)^2) / (pi * (2 / f_number_2)^2) - 1​

    where f_number_1 is the smaller f-number (like 2.8, 1.4, etc.).

    Using the f-numbers you provided, the old camera with an f/2.8 maximum aperture will gather 22.5% more light than the new camera with an f/3.1 maximum aperture. At the other end of the range, the difference increases to 28.7% more light with the old camera. Like steveash said, better image stabilization in the newer camera may help mitigate the light gathering advantage of the old camera. The higher ISO range on the newer camera will help as well, although it will increase sensor noise.

    I should mention that a DSLR camera with a fast prime (fixed focal length) lens is very advantageous in low light situations... This combination at f/1.4 for example can collect over 100x as much light as a P&S in the same amount of time due to the larger aperture area and higher equivalent focal length. Most P&S cameras have very small sensors so their focal lengths and aperture areas are scaled down significantly compared to a DSLR. This is what hurts their low light performance. Being able to gather more light means you can use lower ISO speeds for better image quality, and higher shutter speeds to reduce camera and subject motion. At lower f-numbers you also get reduced depth of field which is great visually but tricky to master.
  8. El Cabong macrumors 6502a

    Dec 1, 2008
    There's not much of a difference.

    You have about a 1/3 stop lost on both ends of the zoom range. Given a single focal length, a 1/15 second exposure at f/2.8 would require about a 1/12 second exposure at f/3.1, which is not a big difference. As far as the f/5.2-f/5.9 change, shooting in low light at those apertures isn't practical in the first place, especially on the tele end of the zoom (i.e. there's really no difference there).

    On an SLR, the difference in these numbers might be worth slight consideration. With a point-and-shoot, they're definitely not worth a second thought.
  9. cupcakes2000 macrumors 6502

    Apr 13, 2010
    You don't need the new camera! AnimaLeo said use your old one, take a picture at 2.8, stop it down to 3.1 and then take another one!
  10. Scuby macrumors regular

    May 16, 2010
    You're assuming the aperture is the only thing that matters.

    I'd suggest that on a compact camera the aperture has only a very small impact on low-light photos. The sensor quality has a much much greater impact, and even at the same apertures the low-light performance is something that a lot of the big manufacturers have been focusing on in the past few years.

    So, if you bought a new camera now (depending on the type, obviously), the increase in low-light performance should generally be much higher than the difference in aperture would suggest.


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