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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)?

AJ Henderson
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user25632
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2 Answers2

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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.

Joanne C
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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.

AJ Henderson
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    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.. – Simeon Pilgrim Jan 28 '14 at 21:40
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    @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. – AJ Henderson Jan 28 '14 at 21:44
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    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. – drfrogsplat Jan 29 '14 at 06:07
  • @Drfrogsplat however a 17x starting at 20 mm is only a 10x starting at 35. – AJ Henderson Jan 29 '14 at 13:41
  • @AJHenderson most "stupid" consumers want flexibility, they understand zoom is the range of wide to zoom they get. As a measure of flexibility it has merit. But to say it's useless, requires to declare all ratios in the known-world are also useless, as they all require understanding what a ratio truly means. But people love ratio's, and misuse them all the time. – Simeon Pilgrim Jan 30 '14 at 21:07
  • @SimeonPilgrim - maybe people have a better understanding of cameras around you than around me, but if I walk in to a best Buy and listen to people talking about cameras, the customers, and half the time the sales people, think that the bigger the x number, the bigger the zoom can make it. They don't understand anything about focal length or that there is a difference in starting point, they just think a bigger x number means it will reach out further, and that is not true. – AJ Henderson Jan 30 '14 at 21:15
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    @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. – Simeon Pilgrim Jan 30 '14 at 21:23
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    @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. – AJ Henderson Jan 30 '14 at 21:52