Crop Factors

Started Sep 20, 2008 | Discussions thread
Sean Nelson
Forum ProPosts: 11,021
Re: No such thing...
In reply to hbx2004, Sep 20, 2008

hbx2004 wrote:

There isn't such thing as "crop factor" for p&s cameras -because
sensor covers full image projected by the lens at it's actual focal length.

From: :

"a crop factor is the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a standard."

The only cameras that don't have a "crop factor" are those which have a sensor (or film) which is the same size as a standard 35mm film frame. On all other cameras, "crop factor" is used to translate a len's focal length into a field of view, expressed in terms of the focal length that would give the same field of view on 35mm film.

So my Canon A650IS camera with it's lens set to 7.4mm gives the same field of view as a 35mm lens would on a 35mm film camera. Therefore it's "crop factor" is a little less than 5.

Another example: my Pentax K100D Super camera uses an APS-C sensor with a crop factor of 1.5. The crop factor is the same whether I use one of my old film lenses which covers an entire 35mm film frame, or one of my new designed-for-digital zoom lenses which only covers the APS-C sensor area and which would vignette if I used it on a film camera.

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