Enlarger

The first patent for a projection photo printing device was obtained in 1843 by William Henry Fox Talbot ^[2] . The calotypy he had invented made it possible to duplicate prints from paper negative, and with the help of the “solar camera” the negative could be increased. Due to many shortcomings, calotypy is not widespread, giving way to the market for photographs of daguerreotype , which allows you to get a single copy of the picture. Duplication of photographs began to be widely practiced only after the invention of the wet collodion process and albumin printing . However, the extremely low photosensitivity of silver chloride albumin photo paper, especially to visible light, prevented optical printing. Until the first decades of the 20th century, contact printing on “daytime” photo papers (albumin, celloidin, and aristotypic), which were exposed through negative sunlight, dominated photography. The exposure time reached 25-30 minutes, which excluded projection printing, coupled with high light losses ^[3] .

One of the first enlargers. 1900 year

The first experiment in optical photo printing was associated with the appearance of highly sensitive gelatin-silver photo papers with a chemical manifestation , the production of which was established in 1879 by Joseph Swan . To enlarge, we used a camera whose frame window was illuminated by daylight through an opening in the wall of a darkened darkroom. A negative was established on the inside of the frosted glass, and the lens built its image on a vertical screen, where a sheet of photo paper was fixed ^[4] . With another method, printing could be carried out in an unshaded room with the help of two cameras of different formats mounted by lenses towards each other. The lens of one of the cameras was retracted, and the joint between the objective boards was isolated from the light. Negative was attached to the frosted glass of a smaller camera, and photo paper was charged into a larger cassette. A white paper reflector was used to illuminate the negative, directing diffused light from the window.

At the beginning of the XX century, some manufacturers of photographic equipment mastered the production of specialized magnifying devices of a similar design. Between two moving boards with negative and photo paper, another one was installed with a lens, and the space between all three was isolated using two focusing bellows ^[5] . The device was equivalent to two cameras with a common lens, and was the first prototype of modern enlargers. A simplified version called “manual magnifying apparatus” or “magnifying cone” was intended for amateur photographers and was designed for a constant magnification factor with a fixed focus lens. For exposure, daylight from the sky was used ^[6] . The most advanced models were equipped with interchangeable photo paper cassettes and the simplest photo shutter ^[7] .

Over time, projection printing with artificial light sources, such as a kerosene lamp , an Auer burner, a Nernst lamp, or a half-watt incandescent lamp, became widespread in professional photography ^[8] . Less often, the negative was illuminated by an arc lamp . Then, to increase the luminous efficiency, they began to use a condenser . The photo enlarger received mass distribution simultaneously with the advent of small-format cameras designed for roller film . To get large enough shots, a small negative required a large increase, and was unsuitable for contact printing. Gradually, the design became vertical, as the most compact for a darkroom, and an incandescent lamp replaced all other types of light sources. With the advent of color multilayer photo paper, professional photo magnifiers began to equip a color mixing head with three retractable absorption light filters ^{[9] [10]} . The design allows you to adjust the spectral composition of negative lighting, performing color correction when printing. Later, these heads were also suitable for printing on multi-contrast photo paper , as well as those specially designed for them ^[11] .

The simplest enlarger consists of a lantern, which is moved by a special mechanism relative to the horizontal base. A light source (most often an incandescent lamp ), a negative holder and a lens are located in a lantern ^[12] . Under the lens there is usually a hinged frame with red glass, to control the image in red light inactive for black and white photo paper. Vertical movement of the flashlight allows you to steplessly change the increase in negative, and can be carried out as a gear on one or two metal rods, or using a multi-link mechanism such as a pantograph . Lightweight amateur-class devices are equipped with a friction mechanism instead of a gear with a rack. In professional photo magnifiers, an electric drive for lifting the projection head is used. With a large mass of a lantern, it is balanced by a counterweight ^{[13] [14]} . In expensive stationary large-format models, such as the Durst L 1810, both a lantern and a table for a framing frame move along a vertical column ^[15] .

In the simplest amateur and semi-professional photo magnifiers, a horizontal board is used as a base, designed for installation on a table. In professional devices, such as the Soviet "Belarus-2", the table is made as an integral part of the design ^[14] . Known magnifiers with a vertical column, designed for stationary mounting to the wall of a darkroom or a stable base ^[15] . Most vertical photo enlargers allow the lamp to rotate to a horizontal position for projection onto the wall when printing super magnifications ^[16] . In addition, their rod or lifting mechanism can be rotated 180 ° for projection onto the floor ^[17] . For printing in very large formats, there are special projectors of horizontal design, adapted for printing on a vertical sheet ^{[1] [18]} .

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  Portable enlarger

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  Photographic enlarger Filmosto

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  Professional enlarger

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  Large format enlarger

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  Super magnification projector

The main requirement for the lighting system of the enlarger, in addition to sufficient illumination of the negative, is to obtain a uniform exposure throughout the print. There are two fundamentally different ways of lighting the original, giving scattered or directed light. For diffuse lighting, direct or indirect light from one or more lamps, passed through milk glass, is used. The device of a lantern, in which the negative is illuminated by diffused light reflected from a white parabolic reflector, has gained some popularity ^[19] . The second method involves directional illumination of the negative by direct light of a lamp passing through a condenser. In most cases, frosted glass is installed between the lamp and the condenser in condenser photo magnifiers, which slightly softens the contrast due to the Calle effect . Condenser magnifiers are most widely used in photography due to the least light loss ^[20] .

By changing the direction of the illumination of the negative during printing, the contrast of the print can be controlled to a small extent. The most contrasting image can be obtained when using a point source of light in a condenser magnifier without any diffuser. Diffuse illumination produces an imprint comparable in contrast to contact . In addition to contrast, the visibility of mechanical defects and the grain of the negative depends on the degree of directivity of the light. With diffused lighting, they are masked in the best way, and with directional light, they are detected as much as possible. The advantage of non-condenser photo enlargers with reflected light is the absence of the need to adjust the position of the lamp. Specialized color enlargers with a color mixing head, designed for color printing, are built only on this principle, minimizing time-consuming color retouching ^{[21] [22]} .

In the presence of a condenser, fine tuning of the lamp is necessary every time the magnification changes, since even a slight refocusing of the lens disrupts the conjugation ^[17] . This can be neglected only with small movements of the lamp and the presence of a matte diffuser ^[23] . Adjustment is carried out by a special mechanism that allows you to move the lamp inside the lamp and fix it in the desired position. When printing with a point source, reconfiguration is necessary for any change of scale ^[24] . Since the mid-1970s, almost all magnifiers have been equipped with a tray for corrective filters designed for color photo printing ^[25] . Prior to this, models with such a tray were most often additionally indicated by the word “Color” in the name. Typically, the tray is placed between the lamp and the condenser, where the influence of filters on the quality of the optical image is minimal. However, there were also models with the location of the tray between the condenser lenses. Usually the same tray is used to install frosted diffused glass.

Lenses designed for magnifiers have a special design, because in contrast to shooting lenses, their optical calculation is performed not for "infinity", but for finite short distances lying in the range between the main and doubled focal lengths. They differ from other projection lenses by the presence of an iris diaphragm, which allows to increase the depth of field and adjust the exposure when printing ^{[* 1]} . In the USSR, lenses designed for enlargers were marked with the additional letter “U”, for example, “Vega-11U” ^[26] . Abroad, similar optics also have the corresponding marking, for example, “EL Nikkor” ( English EnLarger Nikkor ) ^[27] . In some cases, the use of high-quality shooting lenses is acceptable. Focusing is most often done visually by the sharpness of the image on a table or a sheet of paper. However, there are devices that facilitate aiming: special slot devices in the frame of the negative holder and focuscopes. Some magnifiers are equipped with a device for automatic focusing (“inverter”) using a special pattern and a lever system ^{[28] [17]} .

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  Comparon Lens

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  Vivitar Lens

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  The lens "Vega 11U"

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  Lens "Vega 5U"

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  Industrialar 96U

Professional photo enlargers are equipped with a rotatable objective board , which, combined with the rotation of the flashlight, allows you to correct perspective negative distortions without losing sharpness according to the Scheimpflug principle . This design is typical for magnifiers "Azov", "Belarus-2" and others ^[29] . Stationary magnifiers often combine the function of a reproduction unit. Their set includes illuminators and an attachment for photographing or a camera mount bracket ^[30] .

In condenser photo magnifiers, the optical system is constructed so that the condenser builds an image of the filament of the lamp in the entrance pupil of the lens ^[20] . Therefore, in addition to the exact alignment of the lamp, it is necessary to adjust its position relative to the condenser depending on the focus. After selecting the image scale and focusing, the frosted glass is removed from the lamp (if available), and the negative that interferes with the lighting assessment is removed from the negative holder ^[31] . The lamp bar is at its position when the frame window is lit most evenly ^[32] . Sometimes the adjustment is made both with the aperture open and with its working value, since in the latter case the position of the lamp is determined more precisely. Then frosted glass and negative are inserted back and printing is made ^[33] .

Universal photo magnifiers designed to print negatives of various formats are equipped with interchangeable lenses and capacitors. When replacing the lens, the installation of an appropriate condenser is required, since the focal lengths of both optical systems must be consistent. As a rule, large capacitors, designed for a frame with a long diagonal, have a small optical power and are combined with telephoto lenses , giving a proportional zoom scale. Sometimes the condenser does not change entirely, but is equipped with a removable lens, which is installed when using short-focus lenses . The correspondence of a particular condenser to the selected lens is usually described in the magnifier instruction table. If the optics are not properly aligned, normal lamp adjustment and even illumination of the negative may not be possible.

When printing with a point source, setting the lamp position is especially critical. The peculiarity lies in the need to focus the image only with the frosted glass installed, since without it the image sharpness hardly changes during any movement of the lens. This is explained by the structural features of light beams, almost all of the light energy of which is concentrated in the central part corresponding to the minimum aperture ^[24] . However, an unfocused image has a characteristic “smeared” grain texture. After focusing, the frosted glass is removed and adjusted in the same way as for a conventional lamp.

The main attribute by which photo enlargers are classified is the maximum negative format. Professional models are characterized by universality, when the device is suitable for working with both small-format and medium-format negatives. The most expensive photo enlargers, such as Belarus-2, allow you to print almost any negatives from sheet 9 × 12 centimeters to those shot on a narrow 16 mm film ^[14] . Large format enlargers and horizontal projectors are classified as special devices and are used in narrow areas such as printing and photogrammetry . A separate category is made up of portable collapsible photo enlargers, for example, the Soviet UPA family. For carrying or storage, the magnifier and accessories are folded into a special suitcase , which in the working position serves as the base.

Most amateur photo enlargers are designed for printing from small and half format negatives 24 × 36 or 18 × 24 mm in size ( 35 mm film ).

• "Spark"
• "Youth"
• "Don"
• Leningrad
• Tavria

Enlargers for 16 mm film were not produced in the USSR, miniature Kiev-30 cameras were equipped with a negative holder, and inserts for half-format and miniature frames were attached to most magnifiers.

For printing from a wide 60-mm film ( film type 120 ) with negatives 60 × 90 mm medium format enlargers were produced:

• "Neva"
• "Belarus-5"
• Azov

Most medium format enlargers included two capacitors and two or three lenses (for 35 mm and 60 mm film, respectively). This made it possible to ensure high illumination of photo paper and to avoid excessive elevation of the projection head when printing with negatives 24 × 36 mm in size. An insert was used to place a 35 mm film in the negative holder.

Photo Printers

Автоматические принтеры , осуществляющие массовую печать на светочувствительную фотобумагу, в качестве основной функциональной части оснащаются встроенным фотоувеличителем. Отличие от классической конструкции при этом заключается в другом способе изменения формата печати. Увеличение может изменяться ступенчато сменой объективов с фиксированным фокусным расстоянием или с помощью зум-объектива , позволяя печатать снимки разных форматов при неизменном расстоянии между негативом и фотобумагой ^[34] . Последняя подаётся под объектив специальным лентопротяжным трактом, а затем транспортируется в проявочное отделение минифотолаборатории . Негативы также перемещаются в негативодержателе с помощью электропривода.

• «Durst» ( Италия )
• «LPL» ( Япония )
• «Leitz» ( Германия )
• «Kaiser» ( Германия )
• «Dunco» ( Германия )
• «Saunders» ( США )
• «Beseler» ( США )
• « Meopta » ( Чехия )
• «Krokus» ( Польша ) — семейство универсальных фотоувеличителей.

• Photo printing
• Диапроектор

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