SU113884A1 - The method of setting the mode of application, and the device for implementing the method - Google Patents

Description

The control of the process of manifestation is carried out using sensitometric methods - imprinting a wedge, measuring the resulting blackening, building a characteristic curve, etc. The application of these methods requires the presence of special equipment that is not readily available to amateur photographers.

The proposed method and device for carrying out this method makes it easier and more affordable for photo amateurs to establish the mode of application in practical conditions for processing negatives.

The method consists in that two different densities, obtained with a constant, pre-selected interval of exposures, are printed on a positive photographic material, with a higher density being printed directly, and a smaller one through a continuous wedge. After the appearance of the clip on the clip, a point is found for which the sum of the density of the wedge and the small blackening of the test photographic material is equal to the density of the larger blackening of the same material. The degree of density of the wedge, which must be added to equalize the density of areas with large and small blackening, judge the degree of manifestation.

FIG. 1 and 2 illustrate the principle of determining the degree of manifestation.

FIG. 1 accept designations; (-continuous optical wedge, 2 — developed photographic material with two sections having different density and 5 — photo paper on which printing is made.

After the appearance of the imprint, the points of the same blackening are found on it (in the figure such points are conventionally denoted by the index x) and the magnitude of the degree of manifestation is counted.

A device for implementing the described method may

be made in the form of a glass plate having three floors (not

CALCTIONS of areas covered with light protective varnish): floor 4 with optical

density, which usually lies in the linear part of the characteristic no. 113884

the test curve of the test material (for example, with a density of 0.6-0.7) and serving as a reference for comparing with it a section of a low density of negative, a transparent field 5 and a field 6 covered with a continuous optical clip along which the degree of manifestation is applied (on the figure is not shown).

Instead of this scale, two lines 7 can be applied to the wedge, limiting the site of the wedge with normal values of the degree of manifestation from the areas of underexposed or reproducing. For ease of use, the glass plate can be placed in a copy frame or copy machine.

The establishment of the mode of occurrence is as follows.

Any evenly lit surface (cloudless sky, white wall, etc.) is photographed twice in the entire frame so that the ratio of exposures is 1: 2. The last is achieved most easily by photographing with constant exposure at two consecutive aperture numbers. (for example 5, 6 and 8). The exposure is selected in such a way that the negative density of the negative is equal to or slightly higher than the density of the field 4 devices, which ensures that both optical densities are obtained within the straight line portion of the characteristic curve.

After photographic processing, it is first of all convinced that the exposure has been chosen correctly. For this, the unexposed area of the developed negative is placed on the field /, and the area with a lower density — on field 2 and a visual comparison is made against the light. After checking the correct exposure, both control frames are placed on the surface of the plate so that the dark frame is on transparent zero 2, and the lighter one is on floor 5, put a sheet of contrasting photographic paper on top and expose it at an average density. If the printout points of the same blackening of both fields will be located in the interval between the two dashes, the time required for the negative to appear is correctly selected; if they are located in the dark end of the imprint, the film is underexposed, and if in the light one, then reproducing.

Subject invention

Claims (3)

1- A method for determining the mode of appearance by the difference of two optical densities lying on the straight line portion of the characteristic curve and obtained with a constant, pre-selected exposure interval, characterized in that, in order to determine the difference of densities without the use of complex instruments, both densities print on photographic paper, with a higher density being printed directly, and a lower one through a continuous wedge and, after visualization, by visual comparison of the blackening of both sections in a section with variable density on The point for which the sum of the density of the wedge and the small blackening of the test material was equal to the density of the greater blackening of the same material and the value of the density of the wedge, which needed to be added to equalize the densities of the sections with small and large blackening, is judged by the degree of events. 2. A device for carrying out the method according to claim 1, characterized in that it is made in the form of a transparent plate (for example, glass), divided into three sections, one of which has an optical density lying in the region of the linear portion of the characteristic curve, the second - transparent, and the third - covered with a continuous wedge, along which the scale of the degree of manifestation is applied. 3. A device according to claim 2, characterized in that two lines are applied on the wedge, limiting the site of the wedge with normal values of the degree of manifestation from the areas of underproduction and reproducing.