Photography
About Photography:
- The art or process of producing images of objects on photosensitive surfaces.The art, practice, or occupation of taking and printing photographs
- It was developed in the 19th century through the artistic aspirations of two Frenchmen, Nicéphore Niepce and Louis-Jacques-Mandé Daguerre, whose combined discoveries led to the invention of the first commercially successful process, the daguerreotype (1837).
- In addition, two Englishmen, Thomas Wedgwood and William Henry Fox Talbot, patented the negative-positive calotype process (1839) that became the forerunner of modern photographic technique.
- In the 1850s and '60s, Mathew B. Brady and Roger Fenton pioneered war photography and photojournalism. From its inception, two views of photography predominated: one approach held that the camera and its resulting images truthfully document the real world, while the other considered the camera simply to be a tool, much like a paintbrush, with which to create artistic statements.
- The latter notion, known as Pictorialism, held sway from the late 1860s through the first decade of the 20th century, as photographers manipulated their negatives and prints to create hazy, elaborately staged images that resembled paintings. By the 1920s and '30s, a new, more realistic style of photography gained prominence, as photographers such as Paul Strand, Edward Weston, and Ansel Adams began to pursue sharply focused, detailed images.
- The Great Depression and two world wars inspired many photographers, including Walker Evans and Dorothea Lange, to pursue documentary, often socially conscious photography. Inspired by such work, many photojournalists, including Alfred Eisenstaedt and Margaret Bourke-White, also emerged during this period.
- In the second half of the 20th century, the urban social scene became a subject of much interest to photographers, as did celebrity portraiture and fashion photography. At the turn of the 21st century, photographers took advantage of digital capabilities by experimenting with enormous formats and new manipulative techniques. As technological advances improve photographic equipment, materials, and techniques, the scope of photography continues to expand enormously.
Photography Functions:
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.
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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.
Image capture can be achieved through various combinations of shutter speed, aperture, and film or sensor speed. Different (but related) settings of aperture and shutter speed enable photographs to be taken under various conditions of film or sensor speed, lighting and motion of subjects and/or camera, and desired depth of field. A slower speed film will exhibit less "grain", and a slower speed setting on an electronic sensor will exhibit less "noise", while higher film and sensor speeds allow for a faster shutter speed, which reduces motion blur or allows the use of a smaller aperture to increase the depth of field. For example, a wider aperture is used for lower light and a lower aperture for more light. If a subject is in motion, then a high shutter speed may be needed. A tripod can also be helpful in that it enables a slower shutter speed to be used.
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. 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
Image examples:
