Photographic cameras

Friday, October 31, 2008

• 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 replace film with 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 motionIn 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:

• Focus - the adjustment to place the sharpest focus where it is desired on the subject.
• Aperture – adjustment of the iris, measured as f-number, which controls the amount of light passing through the lens. Aperture also has an effect on focus and depth of field, namely, the smaller the opening [aperture], the less light but the greater the depth of field--that is, the greater the range within which objects appear to be sharply focused. The current focal length divided by the f-number gives the actual aperture size in millimeters.
• 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. 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. A correct combination of ISO speed, aperture, and shutter speed leads to an image that is neither too dark nor too light.
• Auto-focus 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.

photo gallery

Wednesday, October 1, 2008

Types of Photography

Black-and-white photography:

"Casting Winds" - this black & white displays the classic monochrome look, as well as the use of simulated optical filtering (wratten #25) to enhance or diminish the rendering of certain light wavelengths.
"Casting Winds" - this black & white displays the classic monochrome look, as well as the use of simulated optical filtering (wratten #25) to enhance or diminish the rendering of certain light wavelengths.

All photography was originally monochrome, or black-and-white. Even after color film was readily available, black-and-white photography continued to dominate for decades, due to its lower cost and its "classic" photographic look. It is important to note that some monochromatic pictures are not always pure blacks and whites, but also contain other hues depending on the process. The Cyanotype process produces an image of blue and white for example.

Color photography:

Color photography was explored beginning in the mid 1800s. Early experiments in color could not fix the photograph and prevent the color from fading. The first permanent color photo was taken in 1861 by the physicist James Clerk Maxwell.
Early color photograph taken by Prokudin-Gorskii (1915)
Early color photograph taken by Prokudin-Gorskii (1915)

The first color plate, Autochrome, invented by the French Lumière brothers, reached the market in 1907. It was based on a 'screen-plate' filter made of dyed dots of potato starch, and was the only color film on the market until German Agfa introduced the similar Agfacolor in 1932. In 1935, American Kodak introduced the first modern ('integrated tri-pack') color film, Kodachrome, based on three colored emulsions. This was followed in 1936 by Agfa's Agfacolor Neue. Unlike the Kodachrome tri-pack process, the color couplers in Agfacolor Neue were integral with the emulsion layers, which greatly simplified the film processing. Most modern color films.

Photographic Cameras

People were by far the most common photographic subject of the 19th century. Photographic portraits were much less expensive than painted ones, took less of the sitter’s time, and described individual faces with uncanny accuracy. So great was the sense of presence in these pictures that photographers were often called on to take portraits of the recently deceased, a genre now known as postmortem portraits. Miniature painters, who had previously supplied the least expensive form of portraiture, quickly went out of business or became daguerreotypists themselves.

Interest in daguerreotypes dwindled in Europe after 1851, when English photographer Frederick Scott Archer invented the collodion, or wet-plate process. Like Talbot’s calotype, this was a negative-to-positive process, but because the negatives were made of smooth glass rather than paper, the collodion process produced much sharper images. Glass was also more durable than paper, so it was easier to produce many paper prints from one glass negative.

Using the collodion method, French painter and photographer Adolphe Disdéri in 1854 invented the carte-de-visite, a form of photographic calling card, which soon became the new rage. Taken with a special camera that produced eight poses on one negative, the carte-de-visite—and its larger sibling, the cabinet card—created a market for celebrity photographs in France and England. Cartes, as they are known, were both traded and collected; they served to connect royalty with commoners, actors with their audiences, and old society with the newly prosperous.

In the United States, the carte-de-visite played second fiddle to ever-cheaper variations on the daguerreotype theme. The first of these, the ambrotype, was nothing more than a glass negative backed with black material, which enabled it to appear as a positive image. Patented in 1854, the ambrotype was made, packaged, and sold in portrait studios as the daguerreotype had been, but at a lower cost. Even less expensive was the tintype, patented two years later, which substituted an iron plate for glass. During the American Civil War (1861-1865) tintypes were the most readily available form of location portraiture. Tintype photographers often worked from the back of horse-drawn wagons, photographing pioneer families and Union soldiers.

Photography

Photography is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor. Light patterns reflected or emitted from objects expose a sensitive silver halide based chemical or electronic medium during a timed exposure, usually through a photographic lens in a device known as a camera that also stores the resulting information chemically or electronically. Photography has many uses for both business and pleasure. It is often the basis of advertising and in fashion print. Photography can also be viewed as a commercial and artistic endeavor.

The word "photography" comes from the French photographie which is based on the Greek f?? (phos) "light" + ??af?? (graphis) "stylus", "paintbrush" or ??af? (graphê) "representation by means of lines" or "drawing", together meaning "drawing with light." Traditionally, the product of photography has been called a photograph, commonly shortened to photo.

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 to preserve memories of favorite times, to capture special moments, to tell stories, to send messages, and as a source of entertainment.

Commercial advertising relies heavily on photography and has contributed greatly to its development.