What does a camera's “10x optical zoom” actually mean?
Asked 1/7/2013
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When a camera is advertised with something like a 10x optical zoom, what is that number based on? Is it related to the human eye’s angle of view, or is it just derived from the lens focal-length range?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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It is simply the ratio between the longest focal-length and the shortest focal-length of the camera. For example, if the camera has a 25-100mm range, its zoom is 4X because 100 / 25 = 4.
It does not matter if this is computed based on the actual or equivalent range because the answer will be the same. More importantly, is that two cameras with 10X zooms can have very different ranges, say 25-250mm and 35-350mm, which is why it is better to look at the actual equivalent focal-length instead of zoom ratio. Between these two examples, one camera is much better of architecture (starting very wide at 25mm) and the other for wildlife (reaching much longer at 350mm).
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
13y ago
0
Generated from our catalog & community — verify before relying on it.
“10x optical zoom” is just the ratio of the lens’s longest focal length to its shortest focal length.
Example: a lens with a 25–250mm range is 10x zoom because 250 ÷ 25 = 10. A 35–350mm lens is also 10x because 350 ÷ 35 = 10.
So the zoom number is not based on the human eye. It simply describes how much the focal length changes across the lens’s range.
The important catch is that two cameras with the same zoom ratio can behave very differently. A 25–250mm lens starts wider, which is better for things like architecture or interiors, while a 35–350mm lens reaches farther, which can be better for wildlife or distant subjects.
That’s why the actual focal-length range (or 35mm-equivalent range) is usually more useful than the “x” number alone when comparing cameras.
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