What is the canon ef 17 40mm f 4l usm good for?

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From Canon EF 17-40mm f/4L USM: Canon EF 17-40mm f/4L USM: A zoom lens by Canon for Full frame cameras, 17-40mm f/4. An older, light L wide zoom that is plentiful used. Specs - Maker: Canon - Focal length: 17-40mm (zoom) - Maximum aperture: f/4 - Made for: Full frame sensors - Mounts: Canon EF - Stabilised: no - Autofocus: yes What it frames like - On full frame (Canon EF): as marked, 17-40mm. - On APS-C (Canon) (Canon EF): like ...

From Sensor sizes: The main sizes: - Full frame (36 x 24mm, the size of a 35mm film frame). The reference size: when people quote a focal length "in full-frame terms", this is what they mean. - APS-C (about 23 x 15mm). Crop factor about 1.5x (1.6x on Canon). Most entry and mid-range mirrorless cameras. - Micro Four Thirds (about 17 x 13mm). Crop factor 2x. Small, light systems from OM System and Panasonic. - 1-inch ...

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