ISO speed. Basic knowledge

The notion of what ISO sensitivity is, is one of the basic. It is necessary even for a beginner photographer, without him, of course, a professional will not do.

The ISO sensitivity is a measure of the perception of a camera by the matrix of the light it receives. A high ISO level provides an opportunity to take pictures in rooms with insufficient lighting. Just a few years ago, the ISO sensitivity was not a characteristic of the camera, but of the film itself, and to photograph several frames with different levels of illumination, the photographer needed to change the film, choosing the most appropriate one. Today, both professional (mirror and mirrorless) cameras and amateur (digital) cameras have the function of manual and automatic adjustment of the ISO level, which makes it possible to take pictures with different photosensitivity, recording them on the same memory card.

When lighting is insufficient to correctly set the exposure, it is not always possible to use an external (and internal) flash. It is in such cases, and you have to change the ISO value to a higher one, or to switch to its automatic setting.

In addition, adjusting the sensitivity level can help if you can not increase the shutter speed and when there is no tripod. In this case, using higher ISO values will increase the shutter speed.

However, it would be too easy if the continued use of large ISO values had no side effect. After all, the dies for cameras are designed in such a way that an increase in ISO increases their sensitivity. And in this case not only more light is fixed, but also so-called noise.

Determines the range of optimum ISO values for the size of the camera matrix. The higher it is, the lower the noise level even at the maximum ISO values. In cameras (and "mirrors", and "soap boxes"), today, a matrix of at least 2.3 "is installed in the main.

This should be understood in order to prevent a fairly common misconception, sometimes happening with beginners: do not think that the more in a megapixel camera, the better. Just the relatively high number of megapixels that some camera manufacturers are trying to put into the matrix can significantly reduce the quality of images in terms of the occurrence of excessive noise. So do not blindly believe in advertising.

Thus, it is possible to shoot at maximum ISO values only when it is justified:

• If there is a choice between making a picture with noises or not taking pictures at all.
• If the shooting conditions do not allow you to use the flash.
• If you plan to print small photos in which the noise is almost not noticeable.
• If it is possible to reduce the noise level by processing.

And when shooting in an open space with sufficient natural light, the best choice is the ISO sensitivity set to the minimum value. This is how the best shots are obtained.