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What is an exposition in the photo?

All of us know that the exposition is the term relating to exhibitions, displays. In the photo this word gains a few other value. Simple words: exposition this certain amount of light necessary for the correct exhibiting of a photographic material or preparation of the image for display.

The exposition consists of the main three components: photosensitivity (ISO), endurance and diaphragm. Let`s consider that we dealt with ISO.

Endurance - the amount of time during which the lock of the camera is open and passes light on a matrix or a film. It is measured in seconds. The lock can be open long, for example 1 - 3 sec. During this time there can be a lot of things and the moving object of photography in general to leave a shot. To stop the movement there are short excerpts from 1/60 to 1/8000 sec. It is convenient because, for example, with the child or at cross-country race competitions in a different way it will not turn out. It is possible to try to photograph the fountain. On long endurance (to primeru1/30) drops will merge and we will see the flowing water, and on short (1/250) drops will hang in mid-air.

To facilitate work of the photographer the automatic mode of shooting with an endurance priority is thought up. At Nikon it is designated by a letter S, and at Canon Tv. We establish necessary value of endurance, and the camera itself selects necessary value of a diaphragm and will not allow the photographer to make the wrong choice of an exposition.
For change of endurance needs to twist an adjustment castor.

A diaphragm - a changeable opening in a lens. Happens opened and closed. At an open diaphragm (for example F/5) light gets much, and at closed (F/11) it is not enough.
Thereby we regulate amount of light getting on a matrix. But there is one more important parameter which the diaphragm influences - it is depth of sharp space. For example, we want to make a portrait with an indistinct background. For this purpose it is necessary to take away portrayed far away from a background on 1,5 - 2 meters and to open a diaphragm (F/4-F/5). And if we photograph a landscape, then the diaphragm needs to be covered, approximately to F11 value that all space in a shot was sharp.

There is one more automatic mode - with a diaphragm priority. It is designated by letters A or Av. We change a diaphragm at discretion, and the chamber selects necessary value of endurance. For this purpose we twist an adjustment castor.

Happens so that at the choice of necessary value of endurance or a diaphragm other selected value blinks and does not allow to photograph. Says it that lighting insufficient. In this case it is necessary to increase ISO value.

Here also we got acquainted with the basic concepts in the photo.
Exposition = ISO + expopara (vyderzha and diaphragm).

Now it is possible to pass smoothly to studying of completely operated mode - M with use of the exposure meter, amendments of an exposition and power of flash, balance white and a breketing. But all this only after in the head the concept of an exposition strongly settles. Creative achievements!