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For example, there is no mention of the zoom here.

I'm guessing that it's specified in some other specification. If so, what do I look at and how do I compute the zoom from it?

I've looked at a few SLRs and none of them say the zoom. Why do other cameras tell you and these don't (or at least why is the way the information is presented different)?

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  • \$\begingroup\$ You may also find this question useful. \$\endgroup\$
    – AJ Henderson ♦
    Commented Jan 28, 2014 at 20:02
  • \$\begingroup\$ In your link, the zoom range of the bundled lens is the 18-55mm figure mentioned. This basically means "3x" (55/18≈3) but is much more informative once you learn how focal length works. \$\endgroup\$
    – JohannesD
    Commented Jan 28, 2014 at 20:12

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An SLR (digital or otherwise) usually has an interchangeable lens mechanism and given that the "zoom" is a property of the lens, not the camera, it's not possible to tell you on the camera. Basically, all the zoom range is is the ratio between the shortest and longest focal lengths of the lens so, for example, a 10mm - 100mm zoom lens has a 10x zoom ratio.

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The "X" multiplier zoom is simply the longest focal length divided by the shortest and is a misleading number with very little value, even when properly understood, unless you know ether the tightest or widest focal lengths. A 5 to 50mm focal length zoom is technically a 10x zoom, but doesn't cover all that big of a range. A 70 - 400mm zoom on the other hand is barely even a 4x, but will take an image from far further away than the "10x" zoom at 5-50mm.

For photography, focal length and sensor size is what matters. X numbers are just a marketing gimmick with no meaning, so x numbers are not used for higher end photography gear where it is expected those making purchases know that the x number is worthless. Without a starting focal length range the x number is completely meaningless as it tells you nothing about how big the camera will actually make things or how far away it can shoot from.

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    \$\begingroup\$ I wouldn't say the zoom value is 'useless' on fixed lens camera's as it is comparable. But on interchangeable systems is it 'less meaningful' approaching zero.. \$\endgroup\$
    – Simeon Pilgrim
    Commented Jan 28, 2014 at 21:40
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    \$\begingroup\$ @SimeonPilgrim - it's useless due to lack of understanding. Without a measure in focal length, a 30x zoom could give you less magnification than a 2x. It doesn't have any correspondence to what a consumer thinks of when they hear the term. The automatic expectation is that a large zoom means they can take a photo from further away, but there is no validity to that thinking. Though, yes, properly understood, understanding how much play you have is useful. \$\endgroup\$
    – AJ Henderson ♦
    Commented Jan 28, 2014 at 21:44
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    \$\begingroup\$ It's that lack of understanding which makes 'zoom' a useful measure. All consumer fixed-lens cameras start from around 20-35mm (35mm-equivalent) so the zoom value gives you a pretty simple way of comparing them, without having to understand focal lengths (especially given the complexity of widely variable crop-factors in said cameras). It's a single, simple number which is incredibly informative in that context. \$\endgroup\$
    – drfrogsplat
    Commented Jan 29, 2014 at 6:07
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    \$\begingroup\$ @AJHenderson agreed, lots of people don't understand ratios. And stuff up all aspects of life. I'm just arguing for a word change of 'useless' to 'mostly meaningless'. A ratio is not useless, but are mostly meaningless in the real world, but people still compare them, which the shouldn't. But in compact camera's zoom range normally does correlate with zoom reach. \$\endgroup\$
    – Simeon Pilgrim
    Commented Jan 30, 2014 at 21:23
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    \$\begingroup\$ @SimeonPilgrim - ok, that makes sense, let me know what you think of the new wording. I emphasized that it is misleading and that it has very little meaning without knowing one of the focal lengths. \$\endgroup\$
    – AJ Henderson ♦
    Commented Jan 30, 2014 at 21:52

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