المرشحات ( Filters ) .. كتاب فن التصوير الفوتوغرافي

Filters

A filter is used in photography, to improve the image, or to correct some disturbing reflections. It is a piece of colored transparent material that is placed on the lens to isolate unwanted reflections, or to strengthen the impact of a color and mitigate another. Filters are considered secondary photography accessories, but they play an important role in producing a good picture.

The nature of light

To explain the work of filters, a brief presentation of the nature of light is necessary.
White light, or ordinary light, is light that is composed of all the colors of the visible spectrum in equal amounts. This mixture of the colors of the rainbow translates the eye into white.
White light can be decomposed into its color components by passing it through a transparent prism, and obtaining a visible spectrum (we will see this in detail when studying color films).

And all ordinary objects reflect light in uneven values. Something that reflects all colors with the same value appears white, and the thing or things that reflect some of the light falling on them, and reflect colors in varying values, appear gray. Those that absorb the most light and reflect little or no light appear black.

When an object reflects colors unevenly, the object appears colored. For example, a flower that reflects all the red light falling on it and absorbs all other colors. Our eyes only receive red light, and the flower appears to us, so it is red in color! In the same way, if we look through a transparent piece of glass, we see things in their true colour. But if we look through a piece of glass that only allows red color to pass through and absorbs, or intercepts, all other colors, then all things will appear red, because we only see red from the colors reflected on it.

The colored filters used in photography are sheets of glass or plastic, or any other transparent material that has been colored for the purpose of absorbing some colours. There are two types of filters: color filters for black and white photography, and filters
for color photography.
The application of the principles for using filters in black and white photography should not be confused with the principles for their use in color photography.