Basic theoretical knowledge of hyperfocal distance's photography.

The topic of hyperfocal distance's photography has a long history, and it is rarely mentioned in many books about photography. The author found a lot of information and made a research on this topic. There are several issues to be clarified here. 1. What are the practical and practical methods of hyperfocal distance and hyperfocal distance in photography? It is not easy to understand this topic in an easy-to-understand way. But a straightforward explanation can let us photographers know more.

The first basic camera term to be learned here is: What is the blur circle? This is helpful for understanding hyperfocal distance later.

1. What is a fuzzy circle?

This is a key term in our understanding of hyperfocal distance's photography. Fuzzy circle is also called diffusion circle in some photography textbooks.

The concept of fuzzy circle was first put forward by an article published by British photography magazine T.H. in 1866. He found through experiments that when the human eye looks at a picture with a visual distance of 25cm, it can distinguish two lines with a distance of1/4mm in the picture. A 35mm camera negative is enlarged to 20x30 (that is, enlarged by 8 times), and the circle with the diameter = 1/4mm in the photo should be the circle with the diameter of 1/32mm on the negative, which is why camera factories such as Leica later adopted the blurred circle of1/30 mm..

Basic principle of fuzzy circle

The image formed by the point light source on the image plane through the lens is a point, keeping the distance between the lens and the negative unchanged. Move the point light source back and forth along the optical axis, and the image formed on the image plane will become a circle with a certain diameter. The size of the circle depends on the deviation between the lens aperture and the point light source. As long as the diameter of the circular image is small enough and the photo looks clear enough, the circular image of the point light source will appear blurred. This critical point is called a fuzzy circle.

Second, the application of fuzzy circle

What is the diameter of the blur circle of a general 35mm (135) camera lens? 1/30mm, what is the diameter of the blur circle of the medium-sized camera lens? 115 mm, what is the diameter of the fuzzy circle of the miniature camera? 1/60mm. However, the blur circle diameter determined by the camera manufacturer will be slightly different (it is recommended to refer to the camera manual).

Second, what is hyperfocal distance?

Usually, we operate the camera in the process of photography, which is nothing more than automatic (fool mode), program, semi-automatic (aperture priority or speed priority) and full manual. It is true that few people can take photos in hyperfocal distance mode.

To understand and skillfully operate the camera's hyperfocal distance mode, you need to know what hyperfocal distance is first!

Hyperfocal distance is completely different from the above four basic modes. According to the basic principle of fuzzy circle, through the combination of focal length, aperture and distance (focus ring) of camera lens, the maximum depth of field required by photographer can be achieved.

The range of depth of field is very easy for photographers who have some basic theoretical knowledge of photography. But for the above four shooting modes, the problem of depth of field can usually be solved well. However, it is difficult to deal with the depth of field in landscape photography or news documentary photography.

Hyperfocal distance? By combining the focal length, aperture and distance (focus ring) of the camera lens, the photographer applies the principle of camera fuzzy circle to make the subject have a wider range of depth of field from the near boundary of camera depth of field to the far boundary (infinity) of the scene; Similarly, the range of hyperfocal distance can be adjusted by the combination of focal length, aperture and distance (focus ring) of the camera lens.

Hyperfocal distance's calculation formula is:

H=(F？ f)？ (N？ C)+F

The approximate formula of hyperfocal distance calculation is:

H=(F？ f)？ (N？ c)

H= hyperfocal distance (m)

F= focal length value of camera lens (mm)

N= aperture value of camera lens (f)

C= fuzzy circle? 30 lines/mm (the standard value is 30)

Example (approximate formula):

When the focal length of the camera lens is set to 16mm and the aperture is F32, find the hyperfocal distance?

Namely: (16? 16)? (32? 30)

=256? 960

? 0.267m (When one decimal place is reserved, round two decimal places, and? 0.3 meters)

Third, the application of hyperfocal distance in photography creation.

Hyperfocal distance's application in photography mainly includes two aspects. A snapshot photography for documentary (news). As we all know, no matter how fast the camera automatically focuses or the photographer manually focuses, it takes some time. However, if hyperfocal distance photography is used, the parameters can be set in advance according to the needs of photography, without field setting. Photographers can avoid missing opportunities due to operational mistakes, and photographers can completely concentrate on capturing the desired moments and composition. Secondly, in landscape photography, because hyperfocal distance can get a very wide range of depth of field, it can make the near and far scenes clearly appear on the screen. In other words, hyperfocal distance photography can better record and reproduce the whole close shot, middle shot and long shot. Therefore, hyperfocal distance photography is a photography skill that photographers should know and master.

Of course, in the process of applying hyperfocal distance photography, you will encounter exposure problems such as hyperfocal distance. If the exposure time exceeds the limit of manual shooting, use a tripod; If the shooting distance is too close, and indoor photography is not suitable for hyperfocal distance photography because of narrow space or dark light. Hyperfocal distance photography is often ignored by photographers because of the harsh lighting conditions in the shooting process, which is also reasonable. If the shooting conditions permit, I suggest you try it. It will definitely have a different taste.