PHOTOGRAPHY

Photography – China Tdm Over Ethernet – China TDMoIP   by hi joiney

Function The camera or camera obscura is the image forming device and photographic film or a silicon electronic image sensor is the sensing medium The respective recording medium can be the film itself or a digital electronic or magnetic memory Photographers control the camera and lens to expose the light recording material such as film to the required amount of light to form a latent image on film or raw file in digital cameras which after appropriate processing is converted to a usable image Digital cameras use an electronic image sensor based on light sensitive electronics such as charge coupled device CCD or complementary metal oxide semiconductor CMOS technology The resulting digital image is stored electronically but can be reproduced on paper or film The movie camera is a type of photographic camera which takes a rapid sequence of photographs on strips of film In contrast to a still camera which captures a single snapshot at a time the movie camera takes a series of images each called a frame This is accomplished through an intermittent mechanism The frames are later played back in a movie projector at a specific speed called the frame rate number of frames per second While viewing a person s eyes and brain merge the separate pictures together to create the illusion of motion In all but certain specialized cameras the process of obtaining a usable exposure must involve the use manually or automatically of a few controls to ensure the photograph is clear sharp and well illuminated The controls usually include but are not limited to the following Control Description Focus The adjustment to place the sharpest focus where it is desired on the subject Aperture Adjustment of the lens opening measured as f number which controls the amount of light passing through the lens Aperture also has an effect on depth of field and diffraction the higher the f number the smaller the opening the less light the greater the depth of field and the more the diffraction blur The focal length divided by the f number gives the effective aperture diameter Shutter speed Adjustment of the speed often expressed either as fractions of seconds or as an angle with mechanical shutters of the shutter to control the amount of time during which the imaging medium is exposed to light for each exposure Shutter speed may be used to control the amount of light striking the image plane faster shutter speeds that is those of shorter duration decrease both the amount of light and the amount of image blurring from motion of the subject and or camera White balance On digital cameras electronic compensation for the color temperature associated with a given set of lighting conditions ensuring that white light is registered as such on the imaging chip and therefore that the colors in the frame will appear natural On mechanical film based cameras this function is served by the operator s choice of film stock or with color correction filters In addition to using white balance to register natural coloration of the image photographers may employ white balance to aesthetic end for example white balancing to a blue object in order to obtain a warm color temperature Metering Measurement of exposure so that highlights and shadows are exposed according to the photographer s wishes Many modern cameras meter and set exposure automatically Before automatic exposure correct exposure was accomplished with the use of a separate light metering device or by the photographer s knowledge and experience of gauging correct settings To translate the amount of light into a usable aperture and shutter speed the meter needs to adjust for the sensitivity of the film or sensor to light This is done by setting the film speed or ISO sensitivity into the meter ISO speed Traditionally used to tell the camera the film speed of the selected film on film cameras ISO speeds are employed on modern digital cameras as an indication of the system s gain from light to numerical output and to control the automatic exposure system The higher the ISO number the greater the film sensitivity to light whereas with a lower ISO number the film is less sensitive to light A correct combination of ISO speed aperture and shutter speed leads to an image that is neither too dark nor too light hence it is correctly exposed indicated by a centered meter Autofocus point On some cameras the selection of a point in the imaging frame upon which the auto focus system will attempt to focus Many Single lens reflex cameras SLR feature multiple auto focus points in the viewfinder Many other elements of the imaging device itself may have a pronounced effect on the quality and or aesthetic effect of a given photograph among them are Focal length and type of lens telephoto or long lens macro wide angle fisheye or zoom Filters placed between the subject and the light recording material either in front of or behind the lens Inherent sensitivity of the medium to light intensity and color wavelengths The nature of the light recording material for example its resolution as measured in pixels or grains of silver halide Exposure and rendering Camera controls are inter related The total amount of light reaching the film plane the exposure changes with the duration of exposure aperture of the lens and on the effective focal length of the lens which in variable focal length lenses can force a change in aperture as the lens is zoomed Changing any of these controls can alter the exposure Many cameras may be set to adjust most or all of these controls automatically This automatic functionality is useful for occasional photographers in many situations The duration of an exposure is referred to as shutter speed often even in cameras that don t have a physical shutter and is typically measured in fractions of a second Aperture is expressed by an f number or f stop derived from focal ratio which is proportional to the ratio of the focal length to the diameter of the aperture If the f number is decreased by a factor of the aperture diameter is increased by the same factor and its area is increased by a factor of 2 The f stops that might be found on a typical lens include 2 8 4 5 6 8 11 16 22 32 where going up one stop using lower f stop numbers doubles the amount of light reaching the film and stopping down one stop halves the amount of light Exposures can be achieved through various combinations of shutter speed and aperture For example f 8 at 8 ms 1 125th of a second and f 5 6 at 4 ms 1 250th of a second yield the same amount of light The chosen combination has an impact on the final result The aperture and focal length of the lens determine the depth of field which refers to the range of distances from the lens that will be in focus A longer lens or a wider aperture will result in shallow depth of field i e only a small plane of the image will be in sharp focus This is often useful for isolating subjects from backgrounds as in individual portraits or macro photography Conversely a shorter lens or a smaller aperture will result in more of the image being in focus This is generally more desirable when photographing landscapes or groups of people With very small apertures such as pinholes a wide range of distance can be brought into focus but sharpness is severely degraded by diffraction with such small apertures Generally the highest degree of sharpness is achieved at an aperture near the middle of a lens s range for example f 8 for a lens with available apertures of f 2 8 to f 16 However as lens technology improves lenses are becoming capable of making increasingly sharp images at wider apertures Image capture is only part of the image forming process Regardless of material some process must be employed to render the latent image captured by the camera into a viewable image With slide film the developed film is just mounted for projection Print film requires the developed film negative to be printed onto photographic paper or transparency Digital images may be uploaded to an image server e g a photo sharing web site viewed on a television or transferred to a computer or digital photo frame A photographer using a tripod for greater stability during long exposure Prior to the rendering of a viewable image modifications can be made using several controls Many of these controls are similar to controls during image capture while some are exclusive to the rendering process Most printing controls have equivalent digital concepts but some create different effects For example dodging and burning controls are different between digital and film processes Other printing modifications include Chemicals and process used during film development Duration of print exposure equivalent to shutter speed Printing aperture equivalent to aperture but has no effect on depth of field Contrast changing the visual properties of objects in an image to make them distinguishable from other objects and the background Dodging reduces exposure of certain print areas resulting in lighter areas Burning in increases exposure of certain areas resulting in darker areas Paper texture glossy matte etc Paper type resin coated RC or fiber based FB Paper size Toners used to add warm or cold tones to black and white prints Uses Photography gained the interest of many scientists and artists from its inception Scientists have used photography to record and study movements such as Eadweard Muybridge s study of human and animal locomotion in 1887 Artists are equally interested by these aspects but also try to explore avenues other than the photo mechanical representation of reality such as the pictorialist movement Military police and security forces use photography for surveillance recognition and data storage Photography is used by amateurs to preserve memories of favorite times to capture special moments to tell stories to send messages and as a source of entertainment History Main article History of photography First known surviving heliographic engraving made by Joseph Nicphore Nipce in 1825 by contact under an engraving with the heliographic process This seminal work has been a step towards the first permanent photography from nature taken with a camera obscura in 1826 Photography is the result of combining several technical discoveries Long before the first photographs were made Chinese philosopher Mo Ti described a pinhole camera in the 5th century B C E Ibn al Haytham Alhazen 9651040 studied the camera obscura and pinhole camera Albertus Magnus 11931280 discovered silver nitrate and Georges Fabricius 15161571 discovered silver chloride citation needed Daniel Barbaro described a diaphragm in 1568 citation needed Wilhelm Homberg described how light darkened some chemicals photochemical effect in 1694 citation needed The fiction book Giphantie published in 1760 by French author Tiphaigne de la Roche described what can be interpreted as photography citation needed Photography as a usable process goes back to the 1820s with the development of chemical photography The first permanent photoetching was an image produced in 1822 by the French inventor Nicphore Nipce but it was destroyed by a later attempt to duplicate it Nipce was successful again in 1825 He made the first permanent photograph from nature with a camera obscura in 1826 However because his photographs took so long to expose 8 hours he sought to find a new process Working in conjunction with Louis Daguerre they experimented with silver compounds based on a Johann Heinrich Schultz discovery in 1724 that a silver and chalk mixture darkens when exposed to light Nipce died in 1833 but Daguerre continued the work eventually culminating with the development of the daguerreotype in 1837 Daguerre took the first ever photo of a person in 1839 when while taking a daguerreotype of a Paris street a pedestrian stopped for a shoe shine long enough to be captured by the long exposure several minutes Eventually France agreed to pay Daguerre a pension for his formula in exchange for his promise to announce his discovery to the world as the gift of France which he did in 1839 Mid 19th century Brady stand photo model s armrest table meant to keep portrait models more still during long exposure times studio equipment nicknamed after the famed US photographer Mathew Brady Meanwhile Hercules Florence had already created a very similar process in 1832 naming it Photographie and William Fox Talbot had earlier discovered another means to fix a silver process image but had kept it secret After reading about Daguerre s invention Talbot refined his process so that portraits were made readily available to the masses By 1840 Talbot had invented the calotype process which creates negative images John Herschel made many contributions to the new methods He invented the cyanotype process now familiar as the blueprint He was the first to use the terms photography negative and positive He discovered sodium thiosulphate solution to be a solvent of silver halides in 1819 and informed Talbot and Daguerre of his discovery in 1839 that it could be used to fix pictures and make them permanent He made the first glass negative in late 1839 In March 1851 Frederick Scott Archer published his findings in The Chemist on the wet plate collodion process This became the most widely used process between 1852 and the late 1880s when the dry plate was introduced There are three subsets to the Collodion process the Ambrotype positive image on glass the Ferrotype or Tintype positive image on metal and the negative which was printed on Albumen or Salt paper Many advances in photographic glass plates and printing were made in through the nineteenth century In 1884 George Eastman developed the technology of film to replace photographic plates leading to the technology used by film cameras today In 1908 Gabriel Lippmann won the Nobel Laureate in Physics for his method of reproducing colors photographically based on the phenomenon of interference also known as the Lippmann plate Processes A filter

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