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Description
Based on the quote "Work harder than you think you did yesterday" by Alex Elle.

--

Photo in the background:

Shot on a Canon 550D

18mm (on the 18-55mm kit lens), making it an equivalent 18mm x 1.6 = 28.8mm
f/3.5
15 seconds

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I was under the impression that EF-S lenses, which were to be used only on bodies with a crop (APS-C) sensor -- such as the one on the 550D -- wouldn't be susceptible to the (1.6x) crop factor. However, EF-S lenses, like all other lenses have a fixed focal length marking, regardless of the crop factor of the camera body.

Thus, even though the EF-S lenses are designed to be used on only APS-C bodies, they are not designed to circumvent the crop factor multiplication. Lens focal length is marked as an absolute value, independent of the crop factor of camera bodies' sensor.

What does differ, however, is the equivalent focal length. So the kit 18-55mm lens is an equivalent 28.8-88mm lens.

In a more extreme example, you'll note that the lens on the iPhone 4 (4s or 5) has a focal length of 3.8mm. But its small size (1/3.2" diagonally) gives it a crop factor of 7.61, making the equivalent focal length 3.8mm x 7.61 = 28.91mm.

Description
Based on the quote "Work harder than you think you did yesterday" by Alex Elle.

--

Photo in the background:

Shot on a Canon 550D

18mm (on the 18-55mm kit lens), making it an equivalent 18mm x 1.6 = 28.8mm
f/3.5
15 seconds

--

I was under the impression that EF-S lenses, which were to be used only on bodies with a crop (APS-C) sensor -- such as the one on the 550D -- wouldn't be susceptible to the (1.6x) crop factor. However, EF-S lenses, like all other lenses have a fixed focal length marking, regardless of the crop factor of the camera body.

Thus, even though the EF-S lenses are designed to be used on only APS-C bodies, they are not designed to circumvent the crop factor multiplication. Lens focal length is marked as an absolute value, independent of the crop factor of camera bodies' sensor.

What does differ, however, is the equivalent focal length. So the kit 18-55mm lens is an equivalent 28.8-88mm lens.

In a more extreme example, you'll note that the lens on the iPhone 4 (4s or 5) has a focal length of 3.8mm. But its small size (1/3.2" diagonally) gives it a crop factor of 7.61, making the equivalent focal length 3.8mm x 7.61 = 28.91mm.