Why are cameras and camera lenses round, while photos and videos are always rectangular screens?

This is related to the polishing method of lens glass. In order to ensure the uniformity and symmetry of lens spherical and aspheric polishing, it is natural that the lens and abrasive keep rotating during polishing, so it is natural that the lens is round and the lens is round.

In addition, when focusing and zooming, some lenses rotate, which is also a reason to make them round.

Question 2. Why are photos and videos always rectangular screens?

Early movies were square, because if they were square, there would be no wasted area between two adjacent movies, and if they were round, imagine two circles.

Nowadays, digital CCD CCD and CMOS image sensor can be made into a circle, and there is no technical problem, but the computers, monitors, televisions, digital photo frames and so on that we all use to look at photos are all square screens, so in order not to waste, the sensors are naturally made into squares.

Let me ask a question.

What is the shape of circular lens imaging?

The answer is also round. The area of lens imaging is larger than that of CMOS, which completely covers CMOS, so the digital camera seems to be a part of lens imaging. In fact, many high-end lenses, such as 70-200mmF2.8, have square ends, which can block unnecessary light (the part projected outside CMOS) and reduce the influence of unnecessary light.