The difference between digital photography and traditional optical photography

You can basically write a book by asking such a big question. But your question seems to be "the difference between digital photography and traditional film photography" Digital photography is also inseparable from optics, which can only be roughly described here.

From the optical imaging principle of the camera, the two are the same, both of which project the image of the object onto the photosensitive element for imaging. The photosensitive element of traditional film photography is film, which produces a latent image on the film after shooting, and then produces a negative film through development, fixing and development, also called negative film, and then produces a photo through developing and enlarging. The photosensitive element (sensor) of digital photography is CCD or CMOS, which generates electrical signals after shooting, generates images in digital format, and then produces photos through development or printing. At present, the post-processing software of digital photos is very powerful, and it is not too difficult to get started. Most of the general photographic works are post-processed. It turns out that the darkroom in the movie era is very complicated and it is difficult to get started. It's impossible to practice in a few years.

There are also differences between film size and sensor size. Except for professional cameras such as SLR and medium format, the sensor size of general consumer cameras is much smaller than that of 35mm film. Of course, the bigger the sensor, the better the image quality. Furthermore, the camera is no longer mechanical, optical and electronic, but pays equal attention to the three.