RU2029925C1 - Box-type exposure metering calculator - Google Patents

Abstract

FIELD: photography. SUBSTANCE: calculator has a base with scales of exposure values and values of characteristic curve with two or one marks applied onto the base, three plates movably mounted relative to the base with scales of values of diaphragm, exposure times, brightness of white and black standards, respectively: one or two marks corresponding to the marks on the base being applied onto the scale of values of brightness of white and black standards. EFFECT: enhanced accuracy. 4 dwg

Description

 The invention relates to photographic exposure metering and may find application in photography.

 A well-known calculator is an exposure line designed for exposure metering using the characteristic curve of photographic material (Gordiychuk IB, Pepl VG Handbook of a cameraman, M., 1979, p. 343-344; Golovnya A.D. Motion picture exposure. M. , 1966, p. 56-61).

 The specified calculator consists of scales of physical values of apertures, illumination of an object, and reflection coefficient of an object. An exponometric form is inserted into the clip of the calculator, showing the illumination values of the film for the sensitometric series of exposures at a shutter speed of 1/60 s.

 This calculator is more suitable for exposure metering used in cinema. When using this calculator in photography, it is necessary for each exposure to have its own exposure meter form. Scales of illumination of the photo layer are not adjusted for the difference in illumination in the sensitometer and apparatus.

 A known mechanism for determining exposure in a reflex camera equipped with a lens (US patent N 3461783, CL G 01 J 1/10, 1983).

 The exposure calculator (mechanism) consists of disks on which the scales of shutter speed, aperture and film sensitivity are applied. Disks are mounted on a common axis and are frictionally coupled to each other.

 The rotation of the film sensitivity disk by means of a gear transmission is transmitted to the engine of the potentiometer included in the circuit of the galvanometer and photocells, and to an additional rotating aperture scale, the numbers of which are observed in the viewfinder's field of view. The movement of the scales of the calculator is transmitted to the exposure control ring.

 The disadvantages of this calculator are that it does not allow you to use the characteristic curve to calculate the exposure, as well as to predict the density (with some deviation) of individual parts of the frame.

 The aim of the invention is to increase the accuracy of determining exposure, providing the possibility of calculating the density (with some accuracy) of a negative image of the fields of a black-and-white standard, relative to which the densities of individual frame details will be presented, obtaining negatives with the minimum necessary density and thereby increasing the yield of regenerated silver from the fixative solution .

 This goal is achieved by compiling a density calculator for the negative image of the fields of the black-and-white standard according to the characteristic curve of the photographic material. For this, a movable brightness scale of the black-and-white standard and the corresponding scale of illumination of the photo layer in the camera for a normal object with aperture 4, photometrically measured by the densities of the characteristic curve of the film with nominal sensitivity, were introduced.

 The exposure curve of the characteristic curve (at a shutter speed of 1 s) is also used as a scale for the illumination of the photo layer.

 The calculator has a movable aperture and shutter speed scale, a characteristic curve value scale. Scales are labeled for calculations.

 In FIG. 1 shows a calculator in plan; figure 2 presents a diagram of the movement of the scales of the calculator; figure 3 is a black and white standard in plan; figure 4 - reference density in the plan.

 The calculator itself (Fig. 1) is made in the form of a plate 1 with longitudinal recesses of the dovetail type, in which the plates 2-5 move. The plates are marked with scales of apertures (Df), shutter speeds (B), brightness of a black-and-white standard (Sv-2, L-8) (in the designations of specific scales of exposure meters-bright meters "Sverdlovsk-2; Leningrad-8"), scales of the characteristic curve D = f (bgH) (in tabular form). The scale of the characteristic curve is slightly glued to the plate 2. The scale of exposure H, lxC is fixed. It is also used as a scale for the illumination of the photolayer, since at a shutter speed of 1 s the exposure is numerically equal to the illumination of the photolayer.

 For a clear fixation of the scales at each stage in the plates 2-5, there are recesses in which four balls 6 are slightly recessed, located in the four holes of the main plate 1, as in a separator. The balls are pressed by a flat curved spring 7, which is covered by a box-shaped lid 8. The lid is attached to the base with two screws 9.

 The base position of the scales. When exhibiting a black and white standard over a white field, the 4B mark of the Df mark, the 1B mark of the B scale and the 500 B mark of the Sv-2, L-8 scale are opposite the 320B mark of the N.lkhs scale.

 When exhibiting a black-and-white standard over a black field, the above marks 4B, 1B and 500 B are placed opposite the 40-hour mark of the H, lxhc scale.

 The black-and-white standard (Fig. 3) is a card 10 on one side of which a black protective photo paper is glued, with a matte side out, and a white substrate of photo paper is glued on the other side. Thin white marks 11 are applied on the black side of the standard, thin black marks 11 on the white side of the reference.

 The density standard (Fig. 4) is a sensitogram 12, which is sandwiched between two thin glasses 13. On top of the sensitogram, between the glasses, is a strip of paper 11 with the notation of the densitogram field densities. Below the sensitogram, a through gap is left between the glasses, into which the compared sample 15 is inserted and moves along the sensitogram.

 An exponometric calculator is used as follows. At the beginning, the brightness of the black-and-white standard is measured, and then the necessary exposure is calculated by the calculator.

 Around the outstretched arm, normal to the camera and the subject, hold a black and white standard. The viewfinder of the Sverlovsk-2 light meter combines the luminous marks of the viewfinder with 11 marks on the black and white standard and measures the brightness of the white or black field of the standard.

 For example, the brightness of the white field of the standard 125 was obtained. First, it is controlled that the 500 B mark of the Sv-2, L-8 scale is opposite the 320 B mark of the H scale (the base position of the Sv-2 scale, L = 8 relative to the H scale when exposed to a white field reference).

 The mark 4B of the diaphragm scale is set opposite the number 125 of the brightness scale Sv-2, L-8 (figure 2). If you set the mark 1B (1s) of the shutter speed scale opposite the mark 4B of the aperture scale, this will mean that with a brightness of the white field of standard 125, aperture 4 and shutter speed of 1 s, an exposure of 80 lux-h is obtained.

 Select aperture 8. Opposite the number 8 of the Df scale, mark 1B of the B scale. Opposite the necessary shutter speed of the B scale, select the vertical shutter speed necessary for the standard white field density, the D scale. For example, select 1/32 shutter speed, read the estimated shutter speed on the D scale density 1.2.

 If exposed to the black field of the standard, then set the scale of Sv-2, L-8 relative to the scale of H so that the mark 500B of the scale of Sv-2, L-8 is opposite the mark of 50 hours of the scale N. Next, the exposure and density are calculated, as with exposure on the white field of the standard.

 The deviation of the density of the negative invention of the black-and-white standard from the one set during the test shooting is determined using the density standard (Fig. 4).

 If the obtained density of the black-and-white standard differs from the given density (with some deviation) by a certain number of density steps, according to the linear portion of the characteristic curve for a film with a nominal sensitivity, then the current correction and exposure calculation for a given film batch are introduced, i.e. change the basic position of the brightness scale Sv-2, L-8 relative to the H scale (the same is the photolayer illumination scale) by the desired number of steps in one direction or another.

 Using the proposed exposure calculator allows you to get negatives with the minimum required density and, as a result, increase the yield of regenerated silver from the fixative solution.

Claims (1)

 PENAL EXPONOMETRIC CALCULATOR for calculating the shutter speed and aperture value of the camera according to the brightness values of white and black standards, including a base and two plates with aperture value and shutter speed scales, respectively, set with the ability to move relative to the base, characterized in that, in order to increase accuracy by taking into account characteristic curve of the photographic material used, an additional plate with a scale of brightness values of white and black standards and one or two tags si, installed with the possibility of movement relative to the base, and on the base there is a scale of exposure values, a scale of values of the characteristic curve with two or one marks, respectively.

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