Why Compact Cameras' Zoom Lens So Short?


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Apr 15, 2005
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#1
Take for example my Canon S2 IS, it says it has a 35mm equiv. of 36-432mm. But why is the lens barrel so short, compared to SLR lenses?

And i noticed that on the lens, it says 6-72mm. Also, the EXIF of its photos indeed shows 6mm at full wide angle and 72mm at full telephoto. I realized that 6-72mm when multiplied by 6 gives the 36-432mm as stated above. What's the relationship here? Anyone care to explain? :D
 

neoliyam

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Apr 13, 2005
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#2
hello mate,

thats a good question. The equivalent focal length has to do with the crop factor of the sensor inside your camera (the size of the camera sensor relative to a 35mm film). its like getting a crop of the size of your image sensor from the centre of the 35mm film and enlarging it back to 35mm equivalent. this gives you a longer equivalent zoom from a smaller real range (depending upon the crop factor ofcourse).

I hope it helped.

Manish
 

Apr 15, 2005
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#3
Can't really visualize your explanation. :embrass:

I suppose in short, that means a 36-432mm on a compact is very much different from that on a SLR?

If both a compact and a SLR/DSLR(ignoring their crop difference to simplify matters) shoots a same bird at 400mm, am I right to say that the bird on the SLR's picture will be much bigger?
 

majere2sg

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#4
It is something like putting a 67mm lens on the full frame DSLR and crop the picture to the same size as the pns. A full frame DSLR with 400mm lens will resolve more details than a "400mm" PNS although the picture size is about the same.
 

mpenza

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Jan 18, 2002
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#5
The actual lens has a focal length of 6-72mm. it's short and small because it's meant for a small sensor. and because it's a small sensor, the 6-72mm lens will be the equivalent of 36-432mm in 35mm terms (this is just a proxy, you can always convert it to medium/large format equivalent. most of us are used to how wide or tele lenses are in the "film" days).
 

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