أثر بعد أو قرب آلة التصوير من الموضوع الجاري تصويره .. كتاب آلة التصوير

Effect of distance or proximity of the camera to the subject being photographed:

Is it necessary to change the two exposure factors that we estimated when the distance between the camera and the main body is less than it was when photographing from a distance?

This is the question that may come to the photographer's mind when he sees approaching or moving away from the main subject (which happens frequently in the case of cinematography). In response to this question, we say:

First: (a) If the intensity of illumination of the different parts of the scene is close to each other.

(b) The photography was in daylight so that the illumination is completely distributed, so the intensity of its illumination will not change whether the camera is close to it or far from it, and therefore the exposure factors are the same.

secondly :

(a) If the filming was in daylight.

(b) There was a difference between the intensity of illumination of one part of the scene and its neighbours.
It is necessary to increase the exposure if the camera approaches the part that is less illuminated, or decrease it if it approaches the part that is more illuminated.

Third :

(a) If the photography is with artificial light sources.

(b) The distance between the light source and the scene being photographed was 1 bit.

(c) The intensity of illumination of the parts of the scene was close to each other. The exposure factor will not change or the camera will approach the body.

Fourthly :

(a) If the photography is with artificial light sources.

(b) The distance between the light source and the scene being photographed was a constant.

(C) There was a difference between the intensity of illumination of one part of the scene
about its neighbourhood.
Then the exposure increases if the camera approaches the part that is less illuminated and decreases if the approach is towards the part that is more illuminated.

Fifth:

(a) If the photography was done with artificial light sources, and the lighting was not
distributed over the entire area evenly.

(b) The camera was fixed in its place.

(c) Moving the main subject in the picture (for example, people moving) away from or close to the light sources.

It is necessary to increase the exposure if the main subject is close to the light source, or decrease the exposure if it is far from the source.

It is necessary to increase the exposure by four times if the distance (between the light source and the main subject) increases by twice, according to the inverse square law.

Sixthly :

(a) If the imaging was with artificial light sources.

(b) The lighting was completely and evenly distributed throughout the area.

(c) If people (actors, for example) move towards or away from the camera, or until the camera moves towards or away from these people, then the exposure factor will not change, as the intensity of illumination of these people (or actors) will not change as long as the lighting remains distributed. And completely equal in this area as a whole.

Important note :

In all the previous cases, we assumed that the photography did not go beyond the limits of the usual standard images. If the photography was close-up, all the previously explained rules apply regarding the new focal number after placing additional lenses or increasing the extension of the bellows.

Notes on using exposure meters:

1- Before starting the measurement, it must be verified whether or not the scale has been adjusted according to the speed and sensitivity of the pen.

2- The sensitivity of the meter must be verified by pointing it towards a strong light source and observing the movement of the pointer, then blocking the light from the cell suddenly and verifying that the pointer has returned to the zero mark (which is its place in the absence of rays).

2- The light should be blocked from it whenever possible once the measurement is over. In some types of exposure meters, a light intensity can be placed that increases the sensitivity of the photocell if the light is so weak that it does not affect the cell.

Some causes of misexposure:

By examining the negative image, we may not find that the two exposure factors were correct, despite following all correct measurement methods. Here, the error may be due to any of the following reasons:

(a) The actual shutter speed does not exactly match the speed numbered on the camera maker, whether by an increase or decrease.

(b) The focal numbers do not indicate the intensity of the image's illumination, as a result of a defect in the diaphragm due to the length of use or the removal of the lens coating.

(c) The sensitivity speed written on the film does not properly indicate the sensitivity speed. This is due to the near expiry date of this expiry date, and it has been proven from experiments (1) that the sensitivity of the film decreases by half on its expiry date compared to what it was on the day it was made.

(D) Where the developing process affects the result we get, therefore it is likely that the error is not in estimating the exposure factors, but rather due to an error in the display process.

(e) The reason for the error may be due to the photographer's lack of experience in how to use the exposure meter and his knowledge of its characteristics.