Why is Canon's EF-S 15-85mm called a standard zoom while the EF 17-40mm is called ultra-wide?
Asked 2/18/2013
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Canon lists the EF-S 15-85mm f/3.5-5.6 IS USM as a standard zoom, but the EF 17-40mm f/4L USM as an ultra-wide zoom. Is that classification based only on focal length, or does sensor format/field of view matter too?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
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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.
Originally by user11371. Source · Licensed CC BY-SA 4.0
user11371
13y ago
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Generated from our catalog & community — verify before relying on it.
The main difference is angle of view, not just the focal length number printed on the lens.
A lens is called standard, wide, or ultra-wide based on the field of view it gives on the camera it’s designed for. That depends on both focal length and sensor size.
- The EF-S 15-85mm is made for Canon APS-C cameras only. On APS-C, its field of view is roughly equivalent to 24-136mm on full frame, which fits the “standard zoom” category.
- The EF 17-40mm is an EF lens, so it can be used on full frame and APS-C. On a full-frame body, 17-40mm gives an ultra-wide to wide field of view, so Canon markets it as an ultra-wide zoom.
- If you put the 17-40mm on APS-C, its effective field of view becomes about 27-64mm equivalent, which is much closer to a normal/standard zoom range.
So yes: sensor format absolutely matters. The labels describe the resulting view of the image, not just the raw focal length.
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