What do C and Quan Huafu mean in SLR?

Frame C refers to cutting off one end at the left and right ends of the whole frame, with an aspect ratio of 3:2( 16.6x24.9) and a diagonal length of 29.3mm, which is equivalent to 1.7 inch.

Quan Huafu means that the size of the photosensitive area is 36×24 mm..

Quan Huafu is also used to refer to the way that in CCD sensor technology, the content of the sensor covers the whole photosensitive element area, rather than sharing it with pixels related to the same space.

Extended data

The lens of a full-frame camera is installed on an APS-C camera, and the images obtained are different. Because the imaging area obtained by the light passing through the Quan Huafu lens is larger than that of the sensor, the image obtained by the sensor will have a feeling of "the picture is cut" compared with that of the Quan Huafu sensor.

28mm lens is used as a wide-angle lens in a full-frame camera, but when it is used in an APS-C camera, the imaging area becomes narrow and becomes a standard lens. If you want to know what the focal length of Quan Huafu lens on APS-C is comparable to that of a full-frame machine, you must first know the conversion rate. For example, if the conversion rate is 1.6 times, the 28mm wide-angle lens becomes 45mm, which is the standard lens.

This value only describes that the viewing angle is equivalent to the focal length of a Quan Huafu lens, and the perspective relationship will not change. For example, a fisheye lens with exaggerated distortion effect will not become a wide-angle lens.

Baidu Encyclopedia-Quan Huafu

Baidu encyclopedia -APS-C