Photographic plate

In photography, photographic plates have served as the main negative photographic material since the invention of the wet collodion photoprocess , which replaced daguerreotype and calotypy , up to the beginning of the 20th century . The first to use a glass substrate for calotypy instead of a paper one in 1847 was the nephew of Nisefor Nieps Abel Nieps de Saint Victor ^{[2] [3] [4] [5]} . The photosensitive silver halide was held on glass with albumin , subsequently replaced by collodion and then gelatin . From negatives on photographic plates, photographs on photo paper or transparencies on positive photographic plates were printed by contact .

Photographic plates played a large role in astronomy , owing to this photographic material numerous discoveries, such as the discovery of small planets in 1891. After 40 years, due to the comparison of the photographic plates captured by the astrograph with an interval of several days due to the blink-comparator , the discovery of Pluto occurred ^[6] . In astronomy, plates have been used for more than a century to observe celestial bodies and spectrometry . An important advantage over film for a long time was the complete absence of shrinkage after laboratory processing and drying. This allows reliable measurements of certain values ​​in the image.

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  Negative on a glass photographic plate. Moscow 1921

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  Photographic plates in the original packaging. Moscow 1910

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  Cassette for photographic plates of the FKD camera

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  Photographic plate stand at the observatory

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  Soviet glass photographic plates

Beginning in the 1920s with the spread of roller films, plate large-format cameras began to go out of use due to the fragility and heavy weight of the photo material. The remaining equipment of these formats was adapted to sheet photographic film, which replaced the plates in art and household photography. In applications such as astronomy , where shrinkage of film was unacceptable, photographic plates were used until the 1990s. Another area of ​​application of photographic plates was the manufacture of photomasks and printing , but the appearance of phototechnical films on a non-shrink polyethylene terephthalate substrate led to the displacement of glass plates from these industries.

Currently (2017), most manufacturers of photographic materials continue to produce a small assortment of photographic plates designed for applied photography. In Russia, photographic plates are manufactured by the Mikron enterprise, which is part of Slavich OJSC ^[7] . For registration of charged particles and holography, special grades of photographic plates with a thick photoemulsion unsuitable for irrigation on a flexible substrate are produced. There are several manufacturers of liquid emulsions, on the basis of which you can independently prepare glass photographic plates and other photosensitive materials. Photographic plates continue to be used by photographers in old technologies such as ambrotype .

In the 19th century, the sizes of photographic plates were standardized with respect to the basic format, called the “ Whole Plate ”. Its dimensions were 6.5 × 8.5 inches (16.4 × 21.6 centimeters ), and were inherited from daguerreotype ^{[8] [9] [10]} . Smaller formats were obtained by multiple division of the whole plate. So, the “half plate” ( English Half Plate ) had a size of 4.25 × 5.5 inches, and the “quarter plate” ( English Quarter Plate ) was 3.25 × 4.25 inches ^[11] . The proliferation of cheap pocket-sized photo portraits led to even more miniature plates: 1/6 ( Sixth Plate - 2.75 × 3.25 inches), 1/9 ( Ninth Plate - 2 × 2.5 inches) and 1 / 16 ( Eng. Sixteenth Plate - 1⁵ / ₈ × 2¹ / ₈ inches) ^[12] . In Europe, the most common format was considered to be the “third of the record” , also called the “enlarged half”. The frame size was 4.75 × 6.25 inches or 12 × 16 centimeters ^[9] .

Prepared photographs printed by contact were classified in a similar way, but not all sizes of prints coincided with the scale of plate formats: for example, the size of a picture “a quarter” of the whole was 3¹ / ₈ × 4¹ / ₈ inch ^[13] . Among the photographers of the late XIX - early XX centuries, it was common practice to cut large photographic plates, getting a smaller format, so the sizes were often approximate ^[9] . In Russia and the European countries that used the metric system , another standard series was adopted, obtained from the "whole plate" 18 × 24 centimeters. In this case, the “half-plate” format was 13 × 18, and the “quarter of the plate” was 9 × 12 cm. The 24 × 30 plates were called “extra” ^[14] . Formats generally accepted in countries with an English system of measures were often called English in Russia, for example, “a quarter English format”.

The main advantages of glass as a substrate are the invariability of form, unlimited durability and chemical inertness . During archival storage of photographic plates, the aging process affects only the emulsion , in contrast to photographic films, the substrate of which loses its elasticity and warps. Glass for photographic plates is made in accordance with certain requirements for transparency, purity, chemical resistance and mechanical strength. From the point of view of optics, the substrate should be a plane - parallel plate with a strictly constant thickness. For most photographic plates, 0.8–2.0 mm thick glass is used. For large format records (30 × 40 cm or more), thicker glass is used ^[15] .

The disadvantages of photographic plates are their fragility and high weight. Unlike photographic film, which does not react in any way to falling and shock, photographic plates require careful handling. The same supply of photographic material, sufficient for shooting the same number of frames of the same format, weighs several times more on a glass substrate than on a celluloid one. An important disadvantage of photographic plates for a long time was the low efficiency of reloading. However, already at the end of the 19th century, numerous designs of magazine-type cassettes appeared, which made it possible to change the plate within one to two seconds ^{[16] [17] [18]} . They quickly gained popularity in box cameras suitable for sequential shooting. Modern format cameras are suitable for shooting both on photographic plates and on sheet film, the formats of which coincide with the plate ones. In the latter case, clean glass is inserted into the cassette, on which a film is appliedemulsion out ^[19] .

• Phototechnical film
• Large format

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• Photographic plates for holography (Russian) . 25 lessons of holography . Virtual gallery "Holography". Date of treatment September 10, 2015.