With a fixed focal length and subject distance, an APS-C sensor, for example would just crop the frame compared to a full-frame sensor, not enlarge it. Magnification is a property of the projection, regardless of the size of sensor (or film format) you are using. For example, f/2 on full-frame is equivalent to f/2.8 on medium format in terms of depth of field. APS-C is a stop less than full-frame, and 2 stops less than medium format. For the purpose of subject isolation, f/2 on APS-C has the look of f/2.8 in full-frame and f/4 medium format. Micro 4/3rds is another stop below, and so on down the line. For a lot of photographers, the commonly accepted definition is that a normal lens focal length is determined by the diagonal measurement of the image area, the film frame. For the 24mm x 36mm format of Full Frame, that is 43.3mm and for an APS-C frame, 30.1mm. Photo by pick-uppath via iStock. 50mm lenses on APS-C cameras. If you use a 50mm lens on an APS-C camera then the crop factor of the camera means the 50mm lens is a short telephoto. Combined with the wide aperture of the lens this makes a 50mm lens ideal for portraits on an APS-C camera. Some photographers own both full-frame and APS-C cameras that share the same lens mount. The corrected forumula is: FOV (rectilinear) = 2 * arctan (frame size/ (focal length * 2 * (m+1) )) Where "m" is magnification. At infinity m=0, so the first formula applies. A 50mm lens focused at infinity has a horizontal field of view of about 39.6 degrees for a full frame 35mm camera. 2,360+ Photography Guides & Gear Reviews Full Frame vs. APS-C Cameras (7 Key Differences to Know) Full frame vs. APS-C: which camera sensor is better? Both types have several downsides and advantages. Check out this guide to learn more. Camera Gear Guides | By Jeff Collier Yes a 50mm on an APS-C will have almost the same facial distortion as a 85mm on a full frame (as a 75mm to be exact). So yes, get a 50mm f/1.4 lens for your APS-C body and you will be set to go. However personally I prefer the 90-135mm range on APS-C for head shoots (135-200mm FF equivalency), but a 50mm will do the job. Introduction A 50 mm lens on an APS-C format (crop factor 1.6) images a slightly smaller field of view than a 70 mm lens on a 35 mm camera. The terms crop factor and focal length multiplier were coined to help 35 mm film format SLR photographers understand how their existing ranges of lenses would perform on newly introduced DSLR cameras which had sensors smaller than the 35 mm film format 8G1rIss.