I have a 600D and a 7D and I use the kit lens " EF-S "18-55mm and the 55-250 mm , and I am thinking of buying a 24-105mm f4 IS USM L... so does the EF-S suffer from the same 1.6x crop factor as the EF? For example, the 24-105 IS USM L on an APS-C sensor is like 33mm to 168mm, and the 18-55mm has is equivalent to 28.8-88mm?

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    The crop factor depends on the body (the sensor), so yes it will apply to any lens. See photo.stackexchange.com/questions/38899/… – MikeW Nov 20 '13 at 19:25
  • Also a duplicate of photo.stackexchange.com/questions/38899/… – Michael C Nov 21 '13 at 9:19
  • The EF 24-105mm f/4 L IS is an excellent general purpose lens, but it is a better fit on a full frame camera. For an APS-C body I would consider something that starts in the 17-18mm range. The EF-S 17-55mm f/2.8 is excellent and roughly the same price as the 24-105 since Canon recently lowered the suggested retail prices on several of their lenses. ANd the FoV of 55mm on an APS-C body is the same as 88mm on a FF. Not quite 105mm, but you still have your 55-250. The extra stop of the f/2.8 zoom (compared to f/4) lets you use one stop less ISO which makes up most of the low light hit for APS-C. – Michael C Nov 21 '13 at 9:36

The difference between an EF-s lens and an EF lens is only that an EF-s lens does not project a big enough image circle to cover a full frame and may stick too far in to the camera body to be used safely with full frame cameras.

The focal length is a measure of a physical property of the lens rather than having anything to do with the size of the sensor. We simply refer to an APS-c sensor as being a crop sensor because the 35mm film format was decided as the value for a crop factor of 1.

A 24mm photo is still a 24mm photo regardless of if you take it on an APS-c or a full frame or even a large format camera. The only difference is that the portion of the projected image that is captured is smaller due to the smaller sensor area that is exposed, thus it would require a longer focal length to get an equivalent angle of view from a larger sensor.

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  • @mattdm - good clarification. Didn't think about the fact that 35mm might be confusing with the focal length vs sensor size. – AJ Henderson Nov 20 '13 at 21:57
  • And ,do u think is a good buy ? the 24-105mm F4 is usm L? – user24286 Nov 20 '13 at 23:30
  • @user24286 - it is a nice lens. When I was evaluating, I decided to go with the 24-70 f/2.8 II, but the 24-105 f/4 IS was a strong runner up. – AJ Henderson Nov 20 '13 at 23:38

Your EF-S lenses would be subject to the 1.6x crop factor just as any EF lens would. So your 18-55 kit lens will never show an 18mm FOV, but closer to 29 on the wide end.

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  • I don't think the word "true" is helpful here. The smaller format is just as genuine as the larger one. – mattdm Nov 21 '13 at 11:40

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