Photographic film is a strip or sheet of a transparent plastic film coated on one side with a gelatin emulsion containing a slightly microscopic, light-sensitive silver-halide crystalline. The size and other characteristics of the crystal determine the sensitivity, contrast, and resolution of the film.
Emulsions will gradually become dark if left exposed to light, but the process is too slow and incomplete for practical use. In contrast, very short exposure to images formed by camera lenses is used to produce very little chemical change, proportional to the amount of light absorbed by each crystal. This creates a latent image that is not visible in the emulsion, which can chemically be developed into a visible photo. In addition to visible light, all films are sensitive to ultraviolet, X-ray and high-energy particles. Unmodified silver halide crystals are only sensitive to the blue part of the visible spectrum, resulting in an unnatural appearance of some colored subjects. This problem is resolved by the discovery that certain dyes, called sensitized dyes, when adsorbed onto a silver halide crystal make them respond to other colors as well. First orthochromatic (sensitive to blue and green) and finally panchromatic (sensitive to all visible colors) film is developed. Panchromatic films display all the colors in shades of gray approaching their subjective suitability. With the same technique, special purpose films can be made sensitive to the infrared (IR) region of the spectrum.
In a black-and-white photography film, there is usually a layer of silver halide crystals. When the open halide silver grain is developed, the silver halide crystal is converted into silver metal, which blocks the light and appears as a negative black part of the film. Color films have at least three sensitive layers, combining a variety of sensitive dye combinations. Usually a blue-sensitive layer is on top, followed by a yellow filter layer to stop the remaining blue light from affecting the layer below. Next comes a green-blue sensitive layer, and a red-blue sensitive layer, which records the green and red images respectively. During development, the open silver halide crystal is converted into silver metal, just like a black-and-white film. But in color films, the by-products of the developmental reaction simultaneously combine with chemicals known as color couplers that fall within the film itself or in a developer solution to form a colored dye. Since the by-products are made in direct proportion to the amount of exposure and development, the dye clouds formed are also proportional to exposure and development. After the development, silver is converted back into a silver halide crystal in the bleaching step . This is removed from the film during the process of fixing the image in the film with a solution of ammonium thiosulfate or sodium thiosulfate (hypo or fixer). Fix the leaves behind only the color dye formed, which combine to form a colorful looking image. Then color films, such as Kodacolor II, have as many as 12 layers of emulsion, with more than 20 different chemicals in each layer.
Video Photographic film
Movie history
The earliest practical photographic process was the daguerreotype; it was introduced in 1839 and did not use film. Light-sensitive chemicals are formed on the surface of silver-plated copper sheets. Calotype process produces negative paper. Beginning in the 1850s, thin glass plates were coated with photographic emulsions into standard materials for use in cameras. Although fragile and relatively heavy, the glass used for photographic plates has better optical quality than the original transparent plastic and was initially less expensive. The glass plate continued to be used long after the introduction of the film, and was used for astrophotography and electron micrography until the early 2000s, when they were replaced by digital recording methods. Ilford continues to produce glass plates for specialized scientific applications.
The first flexible photographic roll film was sold by George Eastman in 1885, but the original "film" was actually a layer on the base of the paper. As part of the processing, the image-bearing layer is stripped of paper and affixed to a hard gelatin sheet. The first transparent plastic roll film was followed in 1889. Made from highly flammable nitrocellulose ("celluloid"), now commonly called "nitrate film".
Although cellulose acetate or "safety film" was introduced by Kodak in 1908, it was initially found only a few special applications as an alternative to harmful nitrate films, which had the advantage of being much harder, slightly more transparent, and less expensive. Substitution was completed for X-ray films in 1933, but although safety films were always used for home movies of 16 mm and 8 mm, the nitrate film remained standard for the 35 mm theatrical films until it was finally discontinued in 1951.
Hurter and Driffield began pioneering work on the light sensitivity of photographic emulsion in 1876. Their work allowed the first quantitative size of film speed to be made. They develop the H & amp; D, which is specific to every film and paper. These curves plot the photographic density of the logs of exposure, to determine the sensitivity or speed of the emulsion and enable correct exposure.
Spectral Sensitivity
Early photographic plates and films are very sensitive only to blue, purple and ultraviolet light. As a result, the relative tonal values ​​in a scene are listed approximately as they would appear when viewed through a piece of blue glass. The blue sky with an attractive cloud formation is photographed as empty white. Every detail seen in the mass of green foliage is mainly due to the colorless gloss surface. Bright yellow and red look almost black. Most of the skin tones come out in an unnaturally dark way, and uneven or freckled skin is exaggerated. Photographers are sometimes compensated by adding in the sky from the separate negatives that have been exposed and processed to optimize cloud visibility, manually retouching their negatives to adjust the problem tonal values, and by moistening the face of their caregiver portrait.
In 1873, Hermann Wilhelm Vogel discovered that the sensitivity of the spectrum could be extended to green and yellow light by adding a small amount of a specific dye to the emulsion. The instability of the initial dye and their tendency to quickly cause the fog initially restricted its use to the laboratory, but in 1883 the first commercial dye plates appeared on the market. These initial products, described as isochromatic or orthochromatic depending on the manufacturer, allow more accurate rendering of the colored material into a black-and-white image. Because they are still very insensitive to blue, the use of yellow filters and consequently longer exposure time is required to take full advantage of the expanded sensitivity.
In 1894, LumiÃÆ'¨re Brothers introduced their Panchromatic LumiÃÆ'¨re dish, which was made sensitive, albeit very uneven, for all colors including red. New and improved dyestuffs were developed, and in 1902 Panchromo's much more colorful Panchromo plate was being sold by the German manufacturer Perutz. The commercial availability of highly pigromatic black-and-white emulsions also accelerates the progress of practical color photography, requiring good sensitivity to all spectrum colors for red, green and blue information channels for all captured with reasonable exposure. time.
However, all of these are glass plate based products. Panchromatic emulsions on film bases were not commercially available until the 1910s and were not used in general until some time later. Many photographers who do their own dark work prefer to go without the luxury of a sensitivity to red - a color rare in nature and not common even in man-made objects - rather than being forced to leave the traditional dark space safelight red and process their open films in total darkness. The popular black-and-white snapshot film from Kodak, introduced in 1931, remained an orthochromatic product that was insensitive to red until 1956, when it was replaced by Verichrome Pan. Amateur dark room fans must then deal with films that have not been developed by the sense of touch only.
Color
Experiments with color photography began almost as early as photography itself, but the three-color principle underlying all practical processes was not established until 1855, not shown until 1861, and was not generally accepted as "real" color photography until it became undeniable. commercial reality at the beginning of the 20th century. Although good quality color photographs are being made by the 1890s, they require special equipment, long exposure, printing or the appearance of intricate procedures and highly specialized skills, so they are very rare.
The first commercially successful and commercially successful "film" color is LumiÃÆ'¨re Autochrome, a glass plate product introduced in 1907. It is expensive and not sensitive enough to "snapshot" handheld usage. The film-based version was introduced in the early 1930s and its sensitivity was later enhanced. It is a "mosaic display" product of color additive, which uses a simple black-and-white emulsion coating in combination with a small microscopic color filter element layer. The resulting transparency or "slide" is very dark because the color filter mosaic layer absorbs most of the passing light. The last films of this type were discontinued in the 1950s, but the Polachrome "instant" slide film, introduced in 1983, temporarily revived the technology.
The "color film" in the modern sense of the subtractive color product with multilayered emulsions was born with the introduction of Kodachrome to a home movie in 1935 and as a 35 mm long film for a still camera in 1936. Over the next few decades, color remains much more expensive than black-and-white and requires more light, the factors combined to delay widespread adoption. Decrease in costs and increased sensitivity gradually overcome these obstacles. In the 1970s, color films dominated the consumer market, while the use of black and white films was increasingly limited to photojournalism and art photography.
Effects on lens and equipment design
Lenses and photographic equipment are designed around the film for use. Although the earliest photographic materials are only sensitive to the blue-violet spectrum, some color-corrected acoustic lenses are commonly used, so when photographers carry bright visual yellow rays to sharp focus, the most faintest but most photographic visuals. Active violet rays will also be focused correctly. The introduction of orthochromatic emulsions requires the entire range of colors from yellow to blue to be brought to an adequate focus. Most plates and films depicted as orthochromatic or isochromatic are almost insensitive to red, so that the correct focus of red light is unimportant; a red window can be used to view the frame number on the backing of the roll film, as any red light leaked around the backing will not make the glass frosted; and red lighting can be used in dark spaces. With the introduction of panchromatic films, the entire visible spectrum needs to be brought to an acceptably sharp focus. In all cases, color cast in lens glass or a faint reflection on the image is of no consequence as it will only change a bit of contrast. This is no longer acceptable when using color film. Lenses that are further corrected for newer emulsions can be used with older emulsion types, but are otherwise incorrect.
The development of lens designs for emulsions is then very important when considering the use of old lenses, still often used on large-scale equipment; lenses designed for orthochromatic films may have visible defects with color emulsions; lens for panchromatic film will be better but not as good as the next design.
The filters used are different for different types of movies.
Maps Photographic film
Movie basics
There are several types of photographic films, including: The
- Print film, when developed, produces transparency transparent with light and dark areas and colors (if color film is used) is reversed to their respective complementary colors. This type of film is designed to be printed onto photographic paper, usually by using a magnifying glass but in some cases with contact printing. This paper is then developed. The second inversion that produces returns light, shade and color to their normal appearance. Negative colors incorporate an orange color correction mask that compensates for unwanted color absorption and improves color accuracy in the mold. Although color processing is more complex and more temperature sensitive than black-and-white processing, the wide availability of commercial color processing and scarcity of services for black and white encourages the design of some black-and-white films that are processed in exactly the same way as standard color films.
- Movie reversing produces positive transparency , also known as diapositive . Transparency can be reviewed with the help of magnifier and lightbox. When mounted in a metal frame, plastic or small cardboard for use in a slide projector or slide viewer, it is usually called slide . Reversal films are often marketed as "slide films". Large format flip charts are used by some professional photographers, typically to produce extremely high resolution images for digital scanning into color separation for bulk photomechanical reproduction. Photo prints can be generated from the transparency of the reversal film, but the positive-positive prints to do this directly (eg Ektachrome, Cibachrome/Ilfochrome paper) have all been discontinued, so now require international use to turn positive transparency images into negative transparency, printed as positive prints.
- The black-and-white reversal film exists but is very unusual. Conventional black-and-white negative films can be processed upside-down to produce black-and-white slides, such as dr5 Chrome. Although the chemical kit for black-and-white reversal processing may no longer be available for amateur dark room fans, acid bleaching solutions, the only unusually important component, are easy to prepare from scratch. Black-and-white transparency can also be produced by printing negative to a special positive print film, still available from some specialized photography supply dealers.
To produce a usable image, the film should be well exposed. The amount of exposure variations that can be tolerated by a particular movie while still producing acceptable levels of quality, is called exposure latitude . Color print films generally have greater illumination latitude than other types of films. Additionally, since printed films must be printed for viewing, after-by-fact correction for imperfect exposure is possible during the printing process.
The concentration of the silver halide or crystalline halide remaining in the film after development is referred to as optical density, or just density ; the optical density is proportional to the logarithm of the optical transmission coefficient of the developed film. The dark image on the negative has a higher density than the more transparent image.
Most films are influenced by the silver grain activation physics (which specifies the minimum amount of light required to expose one item) and with random grain activation statistics by photons. The film requires a minimum amount of light before it starts exposure, and then responds with progressive darkening over a wide dynamic range of exposure until all the items are exposed, and the film reaches (after development) its maximum optical density.
During the active dynamic range of most films, the developed film density is proportional to the logarithm of the total amount of light exposed to the film, so the developed film transmission coefficient is proportional to the reciprocal strength of the original exposure brightness. The film image density plot of the exposure log is known as the H & amp; D. This effect is caused by grain activation statistics: as the film becomes more open, each incident photon is less likely to affect unvisited grains, resulting in logarithmic behavior. The simplest and ideal statistical model yields the equation
If the exposed parts of the image are heavy enough to approach the maximum possible density for the print film, then they will begin to lose the ability to show the tone variations in the final print. Usually the area will be considered too bright and will appear as white with no properties in the printout. Some of the issues of tolerance to exposure are very heavy. For example, a bright source of light, such as a light bulb or sun, generally looks best as white without a feature in a mold.
Similarly, if the portion of the image receives less than the initial threshold level of exposure, which depends on the sensitivity of the film to light - or speed - the film there will not have a large enough image density, and will appear on the mold as without properties. black. Some photographers use their knowledge of these limits to determine the optimal exposure for a photograph; for one example, see Zone System. Most automatic cameras instead try to achieve a certain average density.
Movie speed
The film speed illustrates the sensitivity of the threshold of the film to light. The international standard for film rating speed is the ISO scale, which combines ASA speed and DIN speed in ASA/DIN format. Using ISO convention film with ASA 400 speed will be labeled 400/27 Â °. The fourth naming standard is GOST, developed by Russian standard authorities. See article movie speed for conversion table between ASA movie speed, DIN, and GOST.
Common film speeds include ISO 25, 50, 64, 100, 160, 200, 400, 800, 1600, 3200, and 6400. Consumer prints are typically within the ISO 100 to ISO 800 range. Some films, such as Technical Pan Kodak, are not rated ISO and therefore a careful examination of the property of the film must be performed by the photographer prior to exposure and development. The ISO 25 movie is very "slow", as it requires more lighting to produce usable images than the "fast" ISO 800 movie. ISO 800 and larger films are thus more suitable for low light situations and action taking (where short lighting time limits the total received light). The benefit of slower films is that the film usually has fine grain and better color rendition than fast film. Professional photographers of static subjects such as portraits or landscapes usually seek this quality, and therefore require a tripod to stabilize the camera for longer exposure. Professional photography subjects such as fast-moving sports or in low light conditions will definitely choose a faster movie.
Films with a certain ISO rating can be pushed-processed, or "pushed", behaving like a film with a higher ISO, by developing for a longer time or at a higher than normal temperature. Less often, movies can be "drawn" to behave like a "slower" movie. Pushing generally thickens the grain and improves contrast, reduces dynamic range, to damaging the overall quality. However, this can be a useful tradeoff in a difficult shooting environment, if the alternatives can not be used at all.
Custom movie
Instant photography, as popularized by Polaroid, uses special types of cameras and films that automate and integrate development, without the need for further equipment or chemicals. This process is done immediately after exposure, compared to regular films, which are developed thereafter and require additional chemicals. View instant movies.
Films can be made to record invisible ultraviolet (UV) and infrared (IR) radiation. These films generally require special equipment; for example, most photographic lenses are made of glass and therefore will filter most of the ultraviolet light. In contrast, expensive lenses made of quartz should be used. Infrared films can be taken in standard cameras using band- or long-pass infrared filters, although the infrared focus point should be compensated.
Exposure and focusing are difficult when using UV or IR films with cameras and lenses designed for visible light. The ISO standard for film speed only applies to visible light, so the visual spectrum light meter is virtually useless. Film producers can provide the recommended equivalent film speed under different conditions, and recommend heavy groupings (eg, with certain filters, assume ISO 25 in sunlight and ISO 64 under tungsten lighting ). This allows the light meter to be used to estimate the exposure. The focus point for the IR is slightly farther from the camera than visible light, and the UV is slightly closer; this should be compensated when the focus. Apochromatic lenses are sometimes recommended because of their enhanced focus across the spectrum.
An optimized film for X-ray radiation is commonly used for medical imaging by placing the subject between the film and the X-ray source, without the lens, as if a transparent object is imaged by being placed between a standard light source and film.. Unlike other types of films, X-ray films have sensitive emulsions on both sides of the carrier material. This reduces the exposure of X-rays to acceptable images - a desirable feature in medical radiography. The film is usually placed in contact with a thin layer of lead which also increases its sensitivity.
Films that are optimized for the feel of X-rays and for gamma rays are sometimes used for radiation dosimetry and personal monitoring.
The film has a number of disadvantages as a scientific detector: it is difficult to calibrate for photometry, can not be reused, requires careful handling (including temperature and humidity control) for the best calibration, and the film must be physically returned to the laboratory and processed. To this, photographic film can be made with higher spatial resolution than other types of imaging detectors, and, because of its logarithmic response to light, has a wider dynamic range than most digital detectors. For example, the Agfa 10E56 holographic film has a resolution of more than 4,000 lines/mm - equivalent to a pixel size of 0.125 micrometers - and an active dynamic range more than five times in brightness, compared to a typical scientific CCD that may have pixels of about 10 micrometers and a dynamic range 3-4 fold.
Special films are used for long exposures required by astrophotography.
Decline
Film remains a dominant form of photography until the early 21st century, when advances in digital photography attract consumers to digital format. The first consumer electronics camera, Sony Mavica was released in 1981, the first digital camera, the Fuji DS-X was released in 1989, coupled with advancements in software such as Adobe Photoshop released in 1989, improvements to consumer-grade digital printers and increasingly widespread computer in households during the late 20th century that facilitate the absorption of digital photography by consumers. Although modern photography is dominated by digital users, the film continues to be used by fans. Movies remain a preference for some photographers because of the distinctive "look".
New interest in recent years
Despite the fact that today's digital cameras are by far the most commonly used photography tool, and that the selection of available photographic films is much smaller than before, photographic film sales have been on a steady up trend, and companies like Kodak, which declared bankruptcy in early 2012, among other companies have noticed this trend, Kodak Alaris's film, paper, and photo chemistry president Dennis Olbrich has stated that sales of their photographic films have grown over the last 3 or 4 years. , UK-based Ilford has also confirmed this trend, and has conducted extensive research on this subject, their research shows that 60% of movie users are currently just starting to use movies in the last five years, and that 30% of current film users under 35 years of age.
In 2013 Ferrania, an Italian-based film producer who discontinued production of photography films between 2009 and 2010, was acquired by the new Ferrania SRL film taking over the company's old manufacturing facility, and rehired several workers who had been laid off 3 years earlier when the company stop film production. In November of the same year, the company started a crowdfunding campaign aiming to raise $ 250,000 to buy equipment and machinery from the old factory, with the intention of putting some of the discontinued movies back into production, the campaign was successful and in October 2014 ended up with more than $ 320,000 raised.
In February 2017, Ferrania Film launched "P30" 80 ASA, Panchromatic black and white film, in 35mm format.
Kodak announced on January 5, 2017, that Ektachrome, one of Kodak's most famous transparency films discontinued between 2012 and 2013, will be reformulated and produced once again, in 35mm and Super 8 movie formats.
Instax movies and Instax "Fujifilm" paper based in Japan have also proven to be very successful, and have replaced traditional photography films as the main product of the Fujifilm film, while they continue to offer traditional photographic films in various formats and types.
DX code
DX coding ( D igital inde X) , or DX codes originally developed by Kodak in the 1980s, and finally adapted by all cameras and film manufacturers. It provides information on both film cassettes and on films regarding the type of film, the amount of exposure, the speed (ISO/ASA rating) of the film. It consists of three types of identification. First is the barcode near the opening of the cassette film, identify the manufacturer, the type of film and the processing method ( see picture below left ). These are used by photofinishing equipment during film processing. The second part is the barcode on the edge of the film ( see picture below right ), used also during processing, showing the type of image film, manufacturer, frame number and synchronizing the frame position. The third part of the DX encoding, known as the DX Camera Auto Sensing (CAS) code, consists of a series of 12 metal contacts on the film cassette, which begins with a camera produced after 1985 can detect the type of film, the amount of exposure and ISO film, and use that information to automatically adjust camera settings for movie speed.
Common movie size
Source:
Company
In production
- ADOX - Made in Germany
- Agfa-Gevaert - Made in Belgium
- Bergger - Made in France
- Lucky - Made in China
- Cinestill - Kodak movie movie modified for C-41 processing
- Printing Dai Nippon - Made in Japan
- FILM Ferrania - Made in Italy
- Foma Bohemia Ltd - Made in Czech Republic
- Fujifilm - Made in Japan
- Ilford - Made in England
- Kodak - Made in the US.
- Mitsubishi Imaging - Made in Japan
- ORWO - Made in East Germany
- Polaroid Originals - Made in Netherlands
- Shanghai - China-made
- Tasma - Russian-made
Stopped
- 3M (Minnesota Mining and Manufacturing Company) - Made in the US, private label film for many chain stores and photofinishing companies; also sold by 3M itself under the trade name Dynachrome
- AgfaPhoto - Branded products previously manufactured by other manufacturers under license
- Ansco - Made in the US ;; in later years known as GAF
- AzoPan - Black and white film, Made in Romania
- AzoColor - Color film, Made in Romania
- DuPont (also DuPont-Pathà ©  ©) - Created in the US.
- Efke - Made in Croatia (production stops in 2012)
- Ferrania (which became Imation and sells the Solaris brand) - Made in Italy
- Forte - Made in Hungary
- Indu - Made in India
- Konica Minolta - Made in Japan
- Maco - Made in Germany
- Perutz - Made in West Germany
- Polaroid Corporation - Made in USA, Mexico, Scotland, and Netherlands
- Seagull - Made in China
- Svema - Made in Ukraine
- VALCA - Made in Spain
- Photon - Made in Poland
Picture gallery
See also
- APUG
- List of photography equipment makers
- List of photography films
- Sensitometry
- Oversamped binary image sensor
Note
References
Bibliography
- Jacobson, Ralph E. (2000). Focal Manual of Photography: Photography and Digital Imaging (9th ed.). Boston, Mass.: Focal Press. ISBN 978-0-240-51574-8.
External links
- Kosmo Articles Photos about film future
Source of the article : Wikipedia
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