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Optical filters preferred method for black and white

Filters were, and still are, shrouded in an air of mystery for newcomers to photography, who are often amazed by the results they see in unusual images they know of course were taken by a filter. Note that filters are very simple, and they are only accessories with many benefits for the photographer, especially with regard to modern black and white films. Filters are rarely necessary for technical work, but their use, based on sound thinking, can make substantial improvements to the appearance of some types of photographs.

There are a large number of black and white filters in the market, and each has its own effect, albeit in relatively varying degrees. Several of them can be used together to get very different shots. We can get an idea of ​​the effect of any filter just by looking through it. But the only way to really know the actual effect of the filter is by experimenting and photographing it directly. Here we have a summary of the basic types of filters, with some examples of the effects they give to the images. Filters and Light Sources One of the tasks of the filters is not to increase the light falling on the film, but rather to reduce it, and it can be removed optionally according to the color of this light and its relationship to the color of the filter used. The task of colored filters is to absorb some colors almost completely, reduce the passage of some other colors, and then allow the rest to pass without any change. Thus, the effect of the used filter depends on the colors it absorbs. The candidate
Yellow, for example, absorbs a large amount of blue light and little red, while it absorbs almost nothing of the yellow and green lights. This means that very few blue reflections will reach the film, while all of these reflections from any source of yellow will seep into the blue targets and so will be relatively darker while the targets
The yellow will be relatively lighter on the level of the printed image compared to the same subject if it was photographed without a filter. Accordingly, the following can be concluded: Each filter emits light while impeding the passage of any other color of its own color well, but at varying rates. Colors that are very far in color from the color of the filter - according to the visible color spectrum - are subjected to strong absorption by the filter, while the absorption is simple for colors that are relatively close to its color. Thus, we can, with careful selection of the color of the filter, control the parts of the image, making some of them light and others dark as we want. The yellow filter uses yellow, for example, to darken the blue sky, and it improves the color contrast in the buildings in front of the blue sky as a background. It will also improve the contrast of shadows and the structure of the snow scenes under Sunlight also removes light haze through the possibility of absorbing ultraviolet radiation, and this possibility is met by most filters. It remains to be mentioned that the yellow filter gives results similar to correcting color sensitivity in black and white film, which makes it similar to the sensitivity of the eye. The green filter broadcasts one-third of the color spectrum. It absorbs a large percentage of blue and red, darkening them, and a very small percentage of green and yellow, making them lighter. It is often used by landscape photographers, as it gives the skin richer light grades. The orange filter: opens both red, orange, and yellow, and closes blue and green. It also helps the appearance to stand out. The surface of the brick or stone buildings, under the sun's rays, making the blue sky very dark. This orange filter can hide spots and skin freckles. The red filter broadcasts a third of the color spectrum according to the intensity of the filter itself. It absorbs the blue and green lights and covers them so that they become close to black, while it works to lighten the red, orange and yellow. The blue filter is the least useful filter, and its usefulness is almost limited to photographing faces - especially the pale blue filter - it works to reduce the paleness of the lips and facial features, and it also increases the visibility of glare in landscapes, but since the panchromatic film can do this task without If a filter is needed, it becomes clear that the blue filter is really the least useful of the other filters. Adjust exposure because the function of color filters is to absorb light reflected from certain colors and turn off the lights
the other and preventing it from reaching the film, so we must compensate when using it. Hence, the manufacturers decided to determine the percentage of this increase according to the density of the filter used. Thus, it can be said that the filter (28) needs twice the exposure determined by the camera, which means opening one stop, or setting the shutter speed in the middle of it (120-200) to increase the exposure for (Shutter speed) We point out here that the reflex SLR camera is equipped to express the exposure ratio automatically through the lens according to the light of the filter. Also, those who have the appropriate exposure and a manual optical reflector can put the filter on a window, calibrated to determine, and in all cases, the type of filter and the meter must be tested Because the color responses of the photometers are not always equal to the responses of the panchromatic film. Testing the filters practically with the photometer available to us is necessary to find the best filter factor for each filter. Finally, it should be noted that overexposure makes the filter relatively less effective. It has no color, and its work is limited to absorbing ultraviolet rays to remove the fog scattered in the sky, as a result of this spectrum.Ultraviolet filters are also used to protect the front of the lens. A lens from sudden shocks and scratches that it may give, and these filters do not need to adjust the exposure. A zero-density filter. This filter works to absorb wavelengths evenly to look gray. It is often used to adjust the exposure, in the event of the need to adopt a wide aperture of the lens with a slow closing speed.
A low-density gelatin filter that sits on top of the flash reflector can be useful from time to time if the flash is too strong or close to the subject... Polarizing filters These filters are used to prevent unwanted reflections from reaching the film. It is provided with supports that allow it to rotate when focused on the lens to adjust the effect given. As for a reflex camera (SLR), we can see the effect of the filter by looking at the subject through the viewfinder while the filter is in place, and here we find that the amount of reflective reduction or darkening of the sky varies according to the angle of the filter and the angle of light.

General Notes

It should be noted first that glass filters are the most common choice, because they are the most suitable for storage and frequent use. We have to take good care of the filters on a permanent basis by returning them directly to their case after use, in order to avoid scratches and even fingerprints, because everything that happens to the filter is like finally. Geometric and formative shapes that contribute to giving artistic effects with good results on photography technology and its development.