This handy rule says that the actual size of the sun on your film or sensor is the lens's focal length divided by 108. This is regardless of the size of the camera format. Don't convert lenses to "35 mm equivalent" or worry about crop factor, etc. Example: a typical Canon APS-C sensor might be 22.2 mm wide by 14.8 mm tall. Thumbtip to little-fingertip = 50mm framing on APS-C, or 80mm on full-frame (click on the image to see it full size). And if I extend my arm, across the peaks of three knuckles spans a 300mm frame. Three knuckles = 300mm framing on APS-C, or 500mm on full-frame (click on the image to see it full size). This is why 35mm at F2 on an APS-C sensor will produce a wider (more in focus) depth of field in comparison to a 50mm at F2 on a full frame sensor, even if the focal length appears the same. Because technically, it's like you’re shooting a full frame 35mm F2 lens on the APS-C camera, just cropping it 1.5x due to the APS-C sensor being OR you can attach an EF-S lens (same mount but opening tailored for the smaller sensor) which holds the focal length true for the APS-C sensor. When inputing the focal length above for a EF Full frame lens attached to the APS-C sensor, I have do the 1.62x calculation first, correct? i.e. an EF 30mm would be effectively a 48.6mm on the APS-C sensor. When I first started with my present DSLR APS-C system that came with a mediocre zoom, I bought 2 full frame lenses, 35 and 50 mm, planning for a future purchase of a full frame camera. Those lenses are still favorites, despite the fact that I have wide angle, telephoto and zoom lenses for the system. So this lens on an APS-C camera will have the same field-of-view as a 52.5mm lens on a full-frame (i.e, 135 format or 35mm - don't get confused with the format being the same as the focal length - it's just a coincidence) camera. A “normal” lens is one that is not telephoto and not wide-angle. This works out be a lens with a focal length about equal to the diagonal measure of the format frame. The Advanced Photo System (APS) frame size is approximately 16mm height by 24mm length. The diagonal measure of this rectangle is about 30mm. APS-C cameras have a crop factor in their lens focal length. Most camera brands such as Sony have 1.5x the stated focal length, whereas Canon is 1.6x. A 50mm Sony APS-C lens is the equivalent of 75mm on a full-frame. .

full frame vs aps c focal length