What does “how much zoom” mean on interchangeable-lens cameras?
Asked 3/6/2011
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I use a Canon camera with 18–135mm and 70–300mm zoom lenses, and people sometimes ask, “How much zoom does your camera support?” For a DSLR or mirrorless camera with interchangeable lenses, what’s the right way to answer? Is zoom simply the focal-length ratio of each lens (for example, 135÷18 = 7.5x and 300÷70 = 4.3x), or is there a better way to explain it?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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As you've pointed out, the question is meaningless in absolute terms. People whose exposure to photography starts and ends with point-and-shoot cameras don't really know what the term means.
They'll be thinking in terms of compact cameras, and the "zoom" on those goes from a moderate wide angle (about the 20mm mark on your lens, which is about 32mm equivalent on a full-frame sensor) as "1" to some multiple. The long end of your telephoto zoom is 300mm, or about "15x" in terms they'll understand.
If they seem disappointed that all you get is "15x" with that "huge" lens, you can always mention that there's an accessory you can get to go to 80x (that'd be the 800mm f/5.6 with a 2x teleconverter, and together they're about the price of an "entry level" automobile, but you don't need to mention that part). That'll kill the disappointment.
Originally by user2719. Source · Licensed CC BY-SA 4.0
user2719
15y ago
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Generated from our catalog & community — verify before relying on it.
On an interchangeable-lens camera, “how much zoom” usually refers to the lens, not the camera body.
For a given lens, the zoom ratio is the long focal length divided by the short one:
- 18–135mm = 7.5x zoom
- 70–300mm = about 4.3x zoom
But that number only describes how much the lens’s focal length changes. It does not tell you absolute “reach.” That’s why your 70–300mm lens has more telephoto reach than the 18–135mm lens, even though its zoom ratio is smaller.
So the best answer is usually:
- “My camera’s zoom depends on which lens I put on it.”
- “This lens is 7.5x zoom,” or “this one goes up to 300mm.”
For people used to compact cameras, saying the maximum focal length is often more meaningful than quoting the zoom ratio alone. Also, high zoom ratios often involve more optical compromises, which is one reason interchangeable-lens cameras use different lenses for different needs.
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