Quote Originally Posted by Sushigaijin
clip..........
You didn't mention which body you have it strapped on but if it is an APS model (most dslrs) than you need to multiply the magnification by the crop factor.

Crop...........
The sensor size does not affect the micro rating 1:2 1:4 1:1 as it is calculated by the image size on the film or sensor and the physical size of the item, size of film/sensor does not factor in. But the size of the sensor/film DOES mater on the apparent focal length (angle of view) APS sized sensor has a factor of angle of view of 1.5. Example a 50mm 35mm film lens will have the angle of view of a 75mm 35mm film lens due to cropping of the image circle of the lens. Now the lenses made for APS sized sensor digital camera if installed on a full fame sensor digital camera will not cover the sensor and you will have a image circle on the film/digital file.