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I own a Canon S95, and am considering getting a newer model (e.g. Canon S110 or S120), and I'm comparing the specs. According to DPReview.com, the S95 has a maximum aperture of F2.0-F4.9, and the S110 has a maximum aperture of F2.0-F5.9. However, I know from using my S95 that I can get an aperture range of F2.0-F8.0. What is the story here? What's the difference between 'maximum aperture' and the aperture I can actually get? I would presume that if there were a maximum aperture, it would be a single number, e.g. maximum F2.0 or F1.4 for a much nicer lens. Why is there a range for the maximum aperture? And how can I effectively compare the specifications for the cameras?

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The lower the number after the F, the more light gets into the camera. More light means - you can get away with shorter exposure times. - you have lower depth-of-field (which is a good thing in portrait shots)

The ranges given for the lenses are the values for the wide angle and the tele setting of the lens.

Generally you want the numbers to be as low as possible, because this is the MAXIMUM aperture. You can close the aperture to something like F/22 or F/30 with all the lenses.

Remember: the reason why bigger numbers mean less aperture is that this really is a ratio. F divided by 2.0 or something.

  • Got it. So if the range for maximum aperture is F2.0-5.9, does that mean that I can only get a maximum of F5.9 in certain conditions? What kind of changing conditions would enable me to get F2.0 vs F5.9? E.g. is one for when I have the widest angle, and the other is when I am more zoomed in? – Jason Jan 14 '14 at 18:54
  • Exactly. If you have the lens on shortes focal lenght (widest angle) you have a maximum of f/2 and if you zoom all the way in, you have a maximum aperture of f/5.9. – Oliver Hankeln Jan 14 '14 at 18:58
  • Great. Is there anywhere that lists the minimum aperture of a camera? I use my camera primarily for photographing documents for my research, and I generally use a smaller aperture to give a wider depth of field, so that more of the item is in focus (especially for books and other documents which are bent or curved, e.g. due to the spine of a book). It seems that most specs I find list the maximum aperture (which I asked about here, and I'm interested in, but I want to know the full aperture range). – Jason Jan 14 '14 at 19:02
  • As a side note, cameras with small sensors (like for example my Panasonic LX5) often have a quite limited minimum aperture (f/8 or so). I suppose this is because of diffraction limits (or some mechanical limitation). – Rmano Jan 14 '14 at 19:49
  • Is this a practical issue for you? Running some numbers via dofmaster, at the wide-angle end of the S110's lens (5.2mm), an aperture of f/5.6 (which yuo can definitely get) and a subject distance of 0.25m, you've already got a depth of field of 0.14m. Stopping down to f/8 will give you 0.21m which I'd imagine is plenty. – Philip Kendall Jan 15 '14 at 9:52
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On a zoom lens, it's common for maximum aperture to vary from one end of the zoom range to the other. Typically, the largest aperture (smallest f-stop number) will be available at the wide end of the zoom range, and it will decrease throughout the range until it reaches the smallest maximum value (yes, it's sort of confusing) at the telephoto end of the zoom ranges.

In your example, the f/8 end of the aperture range is achieved by stopping down the lens -- this value can also vary through the zoom range, but it's less common, and typically isn't as closely scrutinized since people tend to be more interested in wide apertures for letting in lots of light.

Although your example deals with a lens that's fixed to the camera, this variance of maximum aperture across the zoom range happens with interchangeable lenses, too. One of the hallmarks of higher-end zooms, in fact, is a "fixed maximum aperture", which you'll see expressed with a single f-stop value.

[edit] As a final note, prime lenses (lenses that don't zoom), have a single value for maximum aperture intrinsically, because the lens has only one focal length.

  • Got it. So one reason why the S95 has a maximum aperture range of f/2-f/4.9, vs the S110 with a range of f/2-f/5.9 is because the S110 has a longer telephoto? – Jason Jan 14 '14 at 18:58
  • If the lens construction is very similar, that might make sense. Typically, lens construction balances focal length with maximum aperture throughout the range, with more expensive lenses (typically) featuring larger aperture values throughout the range. – D. Lambert Jan 14 '14 at 19:02
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The aperture (the hole inside the lens through which the light passes) can be made very small, but has a limit to how big it can get. The f/ number range given with a camera is the range for furthest open that the lens can get. It is given as a range because when the lens is wide (at short focal lengths) the f/number is smaller than when the lens is zoomed in (long focal lengths).

An f/2 - 5.9 lens does not mean that you can only put the aperture to f/5.9, but rather than when you are at the widest point, you can open the lens to f/2, but when you are zoomed all the way in you can only open it up to f/5.9.

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