Introduction to photography teaches you how to accurately expose.

Lead: Exposure is not absolutely correct, mainly depends on what feelings the photographer needs to express, but the basic knowledge still needs to be understood. Let's teach you how to accurately expose. Let's have a look.

About the same exposure:

We clearly understand such a simple truth: a larger aperture allows more light to pass through the lens to reach the film than a smaller aperture, and a lower shutter speed allows light to stay on the CCD for a longer time than a higher shutter speed. It can evolve into the following situation: the combination of aperture f/ 1.8 and shutter speed 1/500 seconds, and the combination of aperture f/4 and shutter speed1100 seconds, the exposure effect is the same. They are also consistent with the exposure effect obtained by the middle aperture f/8 combined with the medium shutter speed of 1/25 seconds. This is the so-called "equal exposure".

The exposure of the above three groups of exposure combinations is equal, the density reflected on the negative film is consistent, and the tone level and tone reproduction reflected on the CCD are consistent. However, there are two important differences in the picture effect: first, the size of the aperture forms different depth of field; Second, the definition of moving images is different because of the shutter speed.

From the principle of equal exposure, we know that equal exposure with different exposure combinations can obtain the same negative density exposure effect. However, in photography practice, we should choose the best exposure combination among several exposure combinations that can produce the same density according to the difference between the subject and the subject to express the shooting theme. This is the concept of selective exposure.

In terms of exposure control, what is the origin of a satisfactory film?

Those experienced photographers know from the theory and practical experience of photography that although each group of shutters and apertures can produce the same exposure effect, the depth of field and the definition of moving objects in the picture are quite different. Careful consideration must be given to which exposure combination to adopt. Is it possible to get a farther and clearer scene range with a smaller aperture? Or use a higher shutter speed to capture the "frozen image" of the disturbed object? Or use a very short depth of field to blur the background and highlight the subject? Or use a slower shutter speed to enhance the motion of the moving body? Wait a minute.

What is accurate exposure?

In short, the meaning of correct exposure should be: let CCD receive the right amount of light at the right time. Speaking of exposure, I have to talk about Adams' regional exposure first. One of the greatest contributions of American photographer A. Adams, the master of landscape photography, to photography is to create the concept of "regional exposure". Anyway, I don't fully understand it myself. The theory in it is enough to write a book. But now my shooting is based on this part of understanding.

Why can you see the changeable image geometry?

Friends who have learned sketch will easily understand that the picture is nothing more than a continuous transition from white highlights to saturated colors, medium gray to all-black dark parts. This transition enables us to distinguish the outline of an object. The most traditional shooting technique is still the most effective in the digital field. When you see a picture, what do you want to show, that is to say, you want it to reflect the most saturated colors and the richest details. Just aim at it and test it, and then expose it according to the test value, and the resulting film will generally not let you down. Of course, if you want other parts to show a little detail, you must use reflectors and absorbers to control these places within the tolerance of your CCD, or change the angle and other light changes to reduce the light ratio. On the other hand, if you want to make a certain part appear pure black and white, and make these parts deviate from exposure value by more than five grades, you can see what you want to see. Understand the importance of point measurement and manual operation to the camera.

Of course, the actual shooting is not so simple, especially for portraits and documentaries. You have to limit the light, and the light is also limiting you. There is no perfect light unless there are living things in the room. But opportunities are often fleeting. At this time, experience becomes very important. Peripheral exposure is an effective means. But it is not omnipotent, at least peripheral photometry cannot change the objective light ratio. In Bresson's words, "You have to keep changing the angle". Changing the angle is not only to change the composition, but also to improve the restriction of light on you. There are too many things that can be used, such as the reflection of water, white walls, etc., including many unforeseeable situations, such as thin clouds can soften sunlight.

I can't write any more here, but the level is too shallow. Many things can only be understood but not expressed, and it is still very important to think for yourself. As the old saying goes, the key is your brain behind the camera.