Crop factor calculations

The most important parameter for the lens is the horizontal field of view compared to the focal length and crop factors. These are just estimates of the real capability of the camera and will introduce errors if wrongly entered.

The formula for the hfov is \alpha = 2 \arctan \frac {d} {2 f} .
d is 36mm for a full frame film camera, but the sensor for a Sony full frame is only 35.8mm so be careful when calculating the field of view of the Sony full frame cameras.

The sensor size of the Sony APS-C sensor used in the Sony E mounts is 23.5mm.
 If the lens is 16mm, the hfov should be 72.5 degree.

For a full frame 24mm camera, the hfov is 73.7 degree. My Sony E camera taken with 16mm focal length setting has an hfov of 73.7 degree, equivalent to a 24mm full frame.

The cropfactor for the Sony Nex3N is therefore 24/16 which is 1.5.



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