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I was checking the Canon website and found that the EF-S 15-85mm f/3.5-5.6 IS USM lens is a "standard" zoom lens, whereas the EF 17-40mm f/4L USM is described as an "ultra-wide" Zoom.

Is there anything else other than focal length which makes a lens ultra-wide angle or standard zoom?

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3 Answers 3

up vote 11 down vote accepted

The EF-S 15-85 can be used only on APS-C cameras, where it will have an full frame equivalent focal length of 15 * 1.6 to 85 * 1.6 = 24-136mm. As such, it's approximately equivalent to a "normal" zoom on a full frame camera.

The EF 17-40 when mounted on a full frame camera has the stated focal lengths (17-40mm) and is an ultrawide zoom. However, if you mount it on a APS-C camera, its equivalent focal lengths will be 27-64mm and it could be considered to be a normal zoom.

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Thanks for the reply –  Vinod Paul Feb 18 '13 at 9:57

The lenses differ in the sensors they're built for.

EF-S lenses are built for APS-C sensor formats (canon rebel series, 60D, 7D), while EF lenses are for both APS-C and full-frame (6D, 5D's, 1D).

In 35mm equivalents, the EF-S 15-85mm acts as a 24-136mm lens, which is indeed a standard zoom lens, even if a bit long (24-70 can be considered the quintessential standard zoom range). In the same vein, to achieve the same range the EF 17-40mm offers but in APS-C format, you should find yourself something in the vicinity of a 10-25mm. Canon conveniently provides a EF-S 10-22mm lens, although without fixed aperture.

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Thank you Berzemus for the reply –  Vinod Paul Feb 18 '13 at 9:59
    
The EF-S 10-22mm f/3.5-4.5 USM lens has been available from Canon since 2006. –  Michael Clark Feb 18 '13 at 11:18

The terms Ultra-Wide and Standard apply more to the resulting field of view in an image than the actual focal length of the lens used to produce the image. Field of view is a result of both the focal length of the lens and the size of the recording media. In large format photography a 50mm lens is considered Wide Angle. In 35mm photography it is considered Normal. With sensors such as those APS-C size and smaller it is considered Telephoto. In all three cases the description is based on the field of view of the resulting image.

For lenses such as the EF-S 15-85mm f/3.5-5.6 that may only be used on an APS-C camera body the resulting images have the same angle of view as a 24-135mm lens would have on a camera with a 35mm-film sized "full frame" sensor. Thus it is considered a Standard zoom because of the field of view of the photos that can be taken with it. Likewise, if the EF 17-40mm f/4 lens is mounted on an APS-C body, the resulting field of view is equivalent to a 28-65mm zoom lens on a full frame camera. In this case it would also be considered a Standard Zoom Lens. Canon also makes an EF-S 10-22mm f/3.5-4.5 lens that is considered an Ultra-Wide zoom lens on APS-C cameras.

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Thanks Michael :) –  Vinod Paul Feb 18 '13 at 15:35

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