Why do compact cameras offer huge zoom ranges much more cheaply than DSLR lenses?
Asked 10/30/2010
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I’m moving up from a compact camera to a Nikon D3100 and I’m confused about zoom. A $200 point-and-shoot can offer 10x optical zoom or more, but DSLR lenses longer than about 200–300mm get very expensive. Is this mainly because compact cameras use much smaller sensors, so their lenses can be much shorter while still giving a similar field of view? In other words, are compact zooms advertised in “equivalent” terms compared with DSLR lenses?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
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It has to do with the sensor size - large sensors require correspondingly larger lenses. For example, a lens on a small sensor with field of view equivalent to 400mm on full-frame is quite small; 66mm real focal length if I did my math right, and needing to cover a much smaller image circle - both factors which lead to a smaller lens. On the other hand, a 400mm lens for use on a full-frame sensor is a giant $5000 beast. Those really big lenses are expensive because they require huge, precisely manufactured chunks of specialty glass along with the machinery & electronics to focus, zoom, and VR them.
http://en.wikipedia.org/wiki/Image_sensor_format is a good comparison of various common sensor sizes. Your Canon SX120 has a 1/2.5" sensor (5.8x4.3mm), while the D3100 has an APS-C sensor (24x16mm).
Originally by user27. Source · Licensed CC BY-SA 4.0
user27
15y ago
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Yes—sensor size is the main reason. Compact cameras use very small sensors, so they only need short focal lengths to give the same angle of view that would require a much longer lens on a DSLR.
For example, a compact lens might be something like 5–50mm, but because of the tiny sensor it can give a field of view similar to roughly 25–250mm on a larger-sensor camera. A DSLR lens labeled 250mm really has to be 250mm, which means much larger glass elements, a larger image circle, and more demanding mechanical design.
Long DSLR lenses are expensive because they need:
- much larger, precisely made optical elements
- enough coverage for a much larger sensor
- more complex focus/zoom stabilization systems
- high optical quality despite the larger size
So compact cameras often advertise zoom in equivalent terms, while DSLR lenses are specified by their actual focal length. That’s why a small-sensor camera can offer “big zoom” cheaply, while true long telephoto DSLR lenses become large, heavy, and expensive.
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