That big brother knows the relationship between photometry and exposure in photography.

Photometry and exposure, photometry is the basis of exposure, and accurate exposure is the purpose of photometry.

When the camera is running, first measure the light and expose it according to the measured value. Experienced photographers will adjust the luminosity value according to the scene light to achieve more accurate exposure.

For example, before the mechanical camera did not measure light, people decided the exposure according to the characteristics of the film. Generally, there is an exposure meter on the film box. How to adjust the aperture shutter on sunny days and how to adjust it on cloudy days. Now the camera is developed. Without looking at the exposure meter, the camera can calculate the correct exposure value under the current light conditions. The process of calculating the current light intensity is photometry.