العوامل التي تحكم درجة التعريض ( Exposure ) -١- كتاب فن التصوير الفوتوغرافي

Factors that control the degree of exposure (Exposure) -1-

One of us may ask: why the interest in understanding an issue
Exposure If we can get all the information required for that from an exposure table, or by a light-measuring instrument?

This is true, and sufficient if we only want to take normal photos.
But if you want to become a good photographer, amateur or professional, you must understand the basic principles of exposure to give appropriate judgment if the methods of photography are unusual, or to control the information given to you by a light meter.

The factors that control the correct exposure are four:

1- Type of Subject
2- The intensity of the light.
3- The speed of the lens.
4- Film speed or sensitivity.

1- Subject category:
Let us imagine ourselves on the back of a boat in the open sea, where no land can be seen, and where we see only water, sky and clouds. There is nothing in this scene that casts a shadow, and everything is illuminated by sunlight. It is obvious that if we want to take a picture of this scene, we need a very short exposure time.

Let's add to this scene a few boats close to us, this addition gives us some shadows, as picture number 3 shows. If we want to show the details of the boats, some of which are in shadow, we have to increase the exposure somewhat.

Suppose we are back on land, and that we are in a desert, and the sky is clear. If we want to photograph this scene, we need almost the same exposure as in the case of the previous marine scene. If we add to the desert scene elements such as trees, buildings, or a nearby mountain, these elements will block part of the sky's light, and we need to increase the exposure accordingly.