Canon 17-55 IS and Sigma 17-70

Weird question, someone asked me if the canon 17-55 is wider than the sigma 17-70 because of the EF-S mount...is this true? i only thought wideness had to deal with the 17mm x1.6 crop factor...and that would be the same on both lenses on the same canon xti. Could anyone shed some insight? thanks!

When mounted on the same camera, they will give the same field of view at the wide end of their range (17mm).

Originally Posted by NiMSo

When mounted on the same camera, they will give the same field of view at the wide end of their range (17mm).

thanks!

Originally Posted by mok86

Weird question, someone asked me if the canon 17-55 is wider than the sigma 17-70 because of the EF-S mount...is this true? i only thought wideness had to deal with the 17mm x1.6 crop factor...and that would be the same on both lenses on the same canon xti. Could anyone shed some insight? thanks!

from what i understand of it the EF-S mount will allow the field of view to fall onto the sensor perfectly whereas the EF mount allows more to fall beyond the sensor's edges. you will get the same field of view though which is 17mm x 1.6