المرشحات المحايدة التي تقلل من كثافة الضوء ..كتاب التصوير الملون ، عبد الفتاح رياض

The movie was fast! allergy. Neutral density filters: These filters are used if the amount of light is so great that it calls for the use of the narrowest aperture diaphragm in the lens of the camera, especially if. This greatly increases the depth of field. If the photographer desires to reduce the depth of field in some cases (such as if he wants to focus the viewer's attention on the image on a specific subject and not on others), then he is forced to look for a way to reduce the amount of light so that he can widen the aperture of the diaphragm (and thus decrease the depth of field). It may come to mind that this goal is achieved by placing colored light filters in front of the lens, but if this procedure is permissible in some cases of black and white film photography, it is not permissible in the cases of color photography, due to the change in the colors of the image caused by the colored filter. But if the film is in color, then it is a grave mistake to put a colored filter - one of the common filters in black and white film photography - in front of the lens, due to its direct effect on the colors of the image. Therefore, we finally find that the most appropriate way is to use a Neutral filter. It has the ability to absorb part of the light rays falling on it without changing its spectral characteristics, so when it absorbs a part of it, it absorbs all the components of these rays in equal proportions and with complete neutrality, unlike colored filters that absorb between the components of the white rays to the exclusion of others. In this characteristic, the neutral density filter is similar to the polarizing filter. The density of these filters varies, ranging from standing to light gray, and the filter factor also varies according to its density. Table No. (2)

, and shows the data of interest to the photographer when using these filters. It is permissible to combine the neutral density filter with the usual optical filters to correct the colors or to increase the contrast in “black and white” photography, or to adjust the color temperature in color photography (as will come later).