APS-C Lens Crop Factor

[etiennescamera]

As I understand, if using a full frame lens on an APS-C camera, you have to multiply focal length by crop factor to get effective focal length, so my 24-105 effectively becomes 36-157.5 . My question is whether the same applies to lenses designed for APS-C, eg the E 18-135, or does that focal length range already take the crop factor into account?

 

[Uncle Kevriano]

No, any lens on APSC, is multiplied by the crop factor of the sensor, which varies a bit from each manufacturer (1.5 Sony, Nikon, Pentax, 1.6 Canon). The definition of APSC vs FF lenses relates to how they are configured for the sensor.