How serious is the defocusing problem of Canon SLR?

The reasons why the SLR camera is out of focus are as follows:

1。 The main lighting is insufficient.

SLR adopts phase focusing technology and relies on AF sensor to capture light to judge the focusing distance. When the illumination of the subject is insufficient, the light captured by AF sensor is weak, which leads to inaccurate focusing judgment. Therefore, good ambient light is a necessary condition to ensure accurate autofocus of SLR. Of course, at present, the new high-end models adopt newer and stronger AF sensors, and the requirements for illumination can be as low as -3EV or even -4EV, which can cope with focusing shooting under harsh conditions.

2。 The main line is not obvious.

SLR AF sensor is only sensitive to lines. Among the many focuses of the view frame, the focus of the edge is usually a straight line or a single cross, which is only sensitive to horizontal lines or vertical lines, while the focus of the center is usually a double cross (M-shaped), which can identify horizontal lines, vertical lines and diagonal lines. Therefore, the focus of the center point of the SLR camera is more accurate and the edge is weaker. At the same time, when the main body has no obvious lines (such as walls, white paper, sky, flat clothes, etc. ), SLR cameras are difficult to focus accurately.

3。 The focal length of the lens is too short.

The focal length of a lens refers to the distance that the lens moves from infinity to the nearest focal length. Long focal length is beneficial to fine focusing, but it affects the focusing speed of the lens, and is often used for large aperture or telephoto lenses; On the contrary, short focal length is beneficial to fast focusing, but the accuracy is not enough, and it is mostly used for small aperture or wide focal length lenses. Because of the cost, size, positioning and other reasons, manufacturers weigh the trade-offs, and there will be some low-priced lenses with focal lengths that are not conducive to accuracy, which often leads to inaccurate focusing of similar lenses.

4。 The autofocus sensor is displaced.

This situation is usually caused by camera collision, falling and other reasons. Severe vibration leads to slight displacement of AF sensor, which leads to deviation of focusing judgment.

5。 Backlighting

In the case of backlight (such as the sun behind the main body, stage lights, car lights, etc.). ), the main body glare is serious, and it is difficult for the sensor to judge the focus. At this time, photographers usually use manual focusing to focus on other things at the same distance and then lock them back for composition and artificial lighting.

After understanding the above reasons, we can improve the success rate of shooting by thinking about the corresponding coping skills. This is also one of the abilities that photographers must master.

Canon cameras have a reputation as "fleshy" in imaging. With some lenses under certain parameter settings, smoother imaging can be obtained (especially in portrait mode). This feature can't be judged by its merits and has nothing to do with focusing. No matter what machine you have, a photographer can set up a camera, choose a lens and apply light according to his own creative needs, supplemented by good post-correction, and it is by no means a problem to shoot a good film.