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Focusing techniques, problems, and various instruments

The issue of correct focus can be considered the basic essence and starting point for a good picture, and knowing all aspects of this issue is not as easy as some think, but with more knowledge and application, you must achieve the best results in this regard.

We are always faced with photographing any new subject with a confusing question about whether the focus, (*) - focus - is correct or not... The method of focusing the focus of the camera depends, as you know, on determining the most important part of the subject from the point of view of the photographer, and this differs from one photographer to another. . The archaeologist, for example, wants a completely different image from the one that the tourist wants, even if the two images are for the same purpose.

The archaeologist wants a picture that contains a greater amount of information about the buildings and their conditions, while the tourist is interested in taking a picture that reminds him of the atmosphere of the place, without an accurate explanation of its features. Which necessitates multiple focus options here, but in cases where it is difficult to choose a more important part of the subject than others, then it is necessary to ensure that the entire subject is captured within correct focus. Hence - this method can be divided into two parts: optional deliberation and comprehensive deliberation.

Optional sizing:

Optional contrast depends on shooting a field with a blurred depth of vision, isolating or emphasizing the target, and focusing is done in all modern cameras with full aperture until you see the image in the viewfinder, more pure than the final image. In the event that the image is not taken with a full aperture, the depth of field increases when the lens is reduced at the approved aperture. It is necessary, if we want to give a blurry front or back, to zoom out the lens to see the depth of field beforehand, and this is something that most nomadic and semi-automatic cameras allow within their structures in the form of a handle or A conversion button, which is pressed to reduce the lens to the approved aperture, either in cameras with. Viewfinder » There is no alternative to using the depth-of-field scale.

And when we take pictures of paintings, we must be able to delete the background, especially when this takes place in an atmosphere devoid of beautiful backgrounds. Here the close-up lens does the job better than the “standard lens.” 50 mm, while excluding the “wide-angle lens, which is often useless when using optional zoom methods.

In terms of determining the most important part of the image, which should be focused on, in the field of taking pictures of paintings with a wide aperture and within an unclear depth of vision, it is necessary to focus the focus on the perched eyes unless there is a good reason to focus it on the eyes directly - and this painting is the best Among those in which the focus is on the nose, but there are other cases that require the division of the image, according to special considerations. Al-Harbi needed to focus on the hands, for example, instead of the face.

Which attracts attention to the center of concentration - the hands -.
In the case of photographing a natural scene that lacks a point of contrast, it is necessary to focus here on a tree or an isolated wall in the foreground, using a wide aperture that directs attention to one part of the image. This is based on the use of optional contrast, which prevents the viewer's eye from wandering over the entire image.

Mass variance:

Comprehensive contrast is used to benefit from what is available from the depth of field that we adopt for photography, and with knowing the depth of field well, it is easy for us to place what we want from the image within the correct contrast.

This often depends on the focus point in the image, as well as on determining the required aperture. When photographing a distant scene, it is a mistake to believe that the infinity point is the best spot to focus on. If, for example, we are taking a picture with a medium aperture - f / 8 - two centers. Focusing on infinity, the depth of field will extend about thirty feet closer to infinity, with the adoption of the regular lens, and because the field that extends its depth to infinity is of no use, it is recommended to focus the focus on a point closer to make this point of focus sharp, while maintaining the far distance blurry, but if we want to focus the point of focus on infinity for some reason, we have to focus the lens on the suprafocal distance, and this distance varies from one lens to another, and although it is not drawn on the lens barrel, it is easy to find by simply specifying the infinity mark in the lens with the depth of field mark for the aperture used .

To get the most depth in an image that does not include infinity, it is worth not focusing on any specific point, because there is always more depth of field - usually twice as much - and as a result, the best place to focus the lens is about a third of the distance between the nearest sharp point and the farthest.

sizing problems;

There are situations where it is impossible to focus through the lens.
Where the topic freezes when
Point the camera at him...! We have several ways to overcome this problem, the most obvious of which is determining the distance between the camera and the subject, and then expressing the focus on the basis of these measurements.

We can focus the focus on another subject, the same distance away from us, and then direct the focus that has been set towards the original subject.
The shutter (*) is released directly. Another problem is the difficulty of focusing on a reflex camera with a reflex lens, especially in low light conditions, because the viewing apparatus - the mirror, the prism, and the viewing screen - absorbs a large amount of light entering the lens, which increases the difficulty of refraction.

It is also difficult to find a sharp focal point in the case of a wide-angle lens, especially if the lens does not have a very wide aperture.
To solve these two problems, a viewfinder is usually used with these cameras, separate from the capture lens, and this gives the best results for solving low-light problems, because the viewing device absorbs only a very small amount of light.

Focus method:

Simple cameras do not have a way to control the focus of the lens, as they depend on a small aperture that keeps all things sharp, meaning that the focus of the lens is always at the suprafocal distance. Other instruments have a moving scale on the lens with a point or line that determines the focal distance.

These machines are divided into two parts, cameras with one reflex lens. Direct vision cameras

Reflex cameras:

There is a device consisting of a mirror and a prism (*) that project the image onto coated glass in a manner identical to the image on the film. When the image is contrasted on the screen, so that we can see it through the viewfinder, we can be sure that the image on the film will also be sharp.


And most cameras - with a reflex lens - have one or more contrast assistants on the screen. When the target goes out of focus, the line that crosses the center of the central circle divides the image into the obtuse, and they can be reunited by turning the focus ring. There is often a ring consisting of precise “prisms” that divide the subject into a number of small triangles, in case this target is without contrast (*) and here we have to rotate the focus ring until these triangles are illuminated, and many cameras have a regular flat surface or a matte glass It is, of course, difficult to focus with a matte glass, and these tools are designed for use with standard lenses and with wide apertures, because the small aperture here is useless, and it is necessary to focus the focus - if the aperture is like that - with the coated glass piece of the screen.

Direct vision cameras:

In these devices, we see through the viewfinder a slightly dark spot in the form of a circle or square, which gives us a second image in the middle of the image of part of the target that we are photographing, except that it appears strayed to one side, and here we rotate the focus ring on the lens until this dark part coincides With its location in the image, and when they meet, the focus of the lens is focused on the target shown in the dark spot.