Crop Factors

Started Sep 20, 2008 | Discussions thread
PixelMinded
Senior MemberPosts: 1,022
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Re: Crop Factors
In reply to Sean Nelson, Sep 20, 2008

Sean Nelson wrote:

2clueless wrote:

What I was trying to determine is if a crop factor of, say, 5 on a small
sensor point and shoot should be used to determine the "equivalent"
or "apparent" focal length FOV relative to a 35mm film camera just as
it does on dSLR's.

It can, but in most cases compact camera manufacturers already
publish the "35mm equivalent" focal lengths anyway, and they DON'T
publish the crop factors.

But knowing the crop factor does come in handy if you're looking at
EXIF information for a picture and the 35mm equivalent isn't included.

They publish the sensor size and from that you know the diagonal of the sensor, for example G10 has 1/1.7" sensor, which means the diagonal is 9.5mm. Devide the diagonal of 35mmFF ( 43.3mm) by the diagonal of G10 --> 43.3mm/9.5mm = 4.6x (this the crop factor of the G10).
To verivy:

At the wide end of the zoom, G10 is 6.1mm --> 6.1mm x 4.6 = 28mm equivalent. The tele end is 30.5mm x 4.6 = ~ 140mm equiv.

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