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Considerations taken into account when estimating exposure

(a) The solid-coloured objects absorb a large amount of light and reflect differently from the rest, in contrast to the bright or light-coloured objects.

(b) If the photography is during the day, then the two exposure factors differ according to the place and time in which the photography took place. Photography at noon requires an exposure that we estimate at sunset or sunrise, and photography in the shadows differs from the case of photography in direct sunlight, and photography in northern countries. Other than that in the tropics, the two exposure factors that are suitable for the case of photographing in an open place, such as the desert, differ from it if the photography is in a narrow street, for example, or in a closed room, etc.

(c) When photographing with artificial lights, it is noted that the intensity of the object's luminance decreases with the distance of the object from the light source, as the intensity of the luminance is inversely proportional to the square of the distance. Exposure is also affected by the type of lighting. Spot light requires a different exposure than if the light was diffused from a flat reflector.

(d) The exposure factors are estimated according to the speed of the film's sensitivity. If the speed of the sensitivity is reduced by half, the exposure is doubled. Conversely, the exposure is reduced by half, if the speed of the film's sensitivity is doubled.

(e) The estimation of exposure is affected by the spectral characteristics of the film and their suitability for the spectral characteristics of the light sources. What is meant by the spectral characteristics of the film is its sensitivity to different colors of rays, while what is meant by the spectral characteristics of the light source are the colors of the rays emitted by the source, and the amount of energy that it emits from each light wave, which is determined based on what is known as the relative spectral distribution of the spectral energy of the light sources. energy distribution of light sources

It is self-evident that there must be a compatibility between the colors of the rays emitted by the light source and the colors of the rays that the flag is affected by, and the more this compatibility increases, the exposure can be decreased, and vice versa, the exposure must be increased if this compatibility is not complete. If there is no compatibility at all, then there will be no exposure, because how can the exposure be done if the film is not affected by the rays emitted by the light source? ! ! .

(f) Exposure is also affected by whether there is a light filter in front of the lens or not, because the filters absorb some of the light rays that fall on them and allow the rest to pass through, which requires increasing the exposure if we put a light filter in front of the lens. The amount of overexposure (known as the filter factor) depends on
on each of the following factors:

The density of the filter.
2- The spectral sensitivity of the film.
3- Spectral characteristics of the light source.

(g) The exposure estimation is affected by the circumstances in which the film will be shown after shooting, because some exposure solutions may require that the film be overexposed. Over exposure during photography, and we have already talked about this subject in the book (Development, Printing, and Zoom). (1)

(H) Exposure estimation depends on the type of effect and artistic considerations that the photographer desires for the image. In this section, we will talk about these considerations (concerning how and methods of measuring light).

Although we have enumerated in the previous two pages some of the factors that would affect the estimation of the appropriate correct exposure, but the study of the previous factors requires a detailed study that requires extensive independent research, and this is what we did in the second edition of the book (1) The Foundations of Photography, whose chapters are specialized. A detailed study of all these factors (2).