Crop Factors

Started Sep 20, 2008 | Discussions thread
Sean Nelson
Forum ProPosts: 10,263
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Re: Mfr Literature and Sales Pitch Do Matter!
In reply to 2clueless, Sep 20, 2008

2clueless wrote:

If I am looking at a
small sensor point and shoot camera at the local retailer, the sales
rep usually points out that the 28-210mm zoom on the camera has a
great wide angle FOV. However, that is not true. If the "crop" factor
for that particular lens happens to be "5", the effective FOV for
that camera on the "wide" end is really a full frame equivalent of
140mm.

I think you or the salesman is mixing the actual focal length and the "35mm equivalent focal length". For example, if you look at the lens information on Canon web page for the A650:

http://www.usa.canon.com/consumer/controller?act=ModelInfoAct&fcategoryid=183&modelid=15658

it states: 7.4-44.4mm f/2.8-4.8 (35mm film equivalent: 35-210mm)

If the camera saleman tells you that this is a 35-210mm lens, you don't apply the crop factor a second time to come up with the idea that the "wide" end of this lens is equivalent to 175mm on a 35mm camera. He's already quoting you the converted figure.

On the Canon A cameras, at least, the actual focal lengths are engraved on the lens barrel. If there's any doubt as to which focal length someone is talking about, then that's where to look.

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