Special function of electronic rangefinder in photography

The electronic rangefinder in photography seems to have never been heard of.

1. In the 1960s and 1970s, the ranging devices used for cameras were mechanical. The reflection angle of a prism is rotated with a lever, and then reflected on a 40-degree prism, overlapping with the main optical path. The observation method is double shadow superposition (also called macular ranging), which is the method used by cameras such as domestic seagull 205.

2. Later, infrared ranging was used to control the focal length of the lens. This method has a serious disadvantage: when the distance scale of the camera is not accurate, the distance measurement is not accurate. So it was quickly eliminated.

3. The ranging of digital camera is not a concept now. It can focus by directly detecting the clarity of the image, which can ensure the clarity of the photo. Although it is ranging, it is actually a test definition. This is the real "autofocus"

Supplement:

There is an electronic rangefinder in the D60, but it is not clear in the manual, probably because the Japanese can't speak Chinese.

It is actually: the aperture is above 5.6, and in M mode, the camera provides an auxiliary device when you focus manually. It is electronic and can help you focus more perfectly when focusing manually. Because it can be distinguished from autofocus, it is called "electronic rangefinder".

Pages 6 1 and 1 16 of the D60 manual explain this. I've seen it several times, and it's really poor Japanese China, haha.