What effect does Canon Quan Huafu lens used in Canon half-frame SLR cameras have on image quality? Will the resolution be lower? ...

For APS-C format camera, if the standard Quan Huafu lens is used, that is, the lens without -S is used, because the specifications of the imaging photosensitive element are small, only the middle part of the lens is needed, and the outer part of the lens is not needed, so the image quality is better than that of Quan Huafu, and the resolution should also play the best part of the lens, which should be better in theory. However, due to the small area of the photosensitive element (relative to the full frame), especially when the number of pixels reaches more than 20 million, the "photodiodes" in the photosensitive element will be smaller and denser, so there will also be mutual interference. If you want to make a relatively large photo, the defects of mosaic will appear.

Therefore, APS-C camera adopts Quan Huafu lens, which will not reduce the image quality and resolution, but make full use of the best position of the lens. However, due to the small specifications of photosensitive elements, defects such as graininess and mosaic often occur. This is also the motivation for people to use Quan Huafu.