Shutter

In photography, a shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a light-sensitive electronic sensor to light to capture a permanent image of a scene.

Exposure

In photography, exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specified area.

In photographic jargon, an exposure generally refers to a single shutter cycle. For example: a long exposure refers to a single, protracted shutter cycle to capture enough low-intensity light, whereas a multiple exposure involves a series of relatively brief shutter cycles; effectively layering a series of photographs in one image. For the same film speed, the accumulated photometric exposure (H) should be similar in both cases.

Depth of Field

In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. Although a lens can precisely focus at only one distance at a time, the decrease in sharpness is gradual on each side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.

In some cases, it may be desirable to have the entire image sharp, and a large DOF is appropriate. In other cases, a small DOF may be more effective, emphasizing the subject while de-emphasizing the foreground and background. In cinematography, a large DOF is often called deep focus, and a small DOF is often called shallow focus.

The DOF is determined by the camera-to-subject distance, the lens focal length, the lens f-number, and the format size or circle of confusion criterion.

For a given format size, at moderate subject distances, DOF is approximately determined by the subject magnification and the lens f-number. For a given f-number, increasing the magnification, either by moving closer to the subject or using a lens of greater focal length, decreases the DOF; decreasing magnification increases DOF. For a given subject magnification, increasing the f-number (decreasing the aperture diameter) increases the DOF; decreasing f-number decreases DOF.

When the “same picture” is taken in two different format sizes from the same distance at the same f-number with lenses that give the same angle of view, and the final images (e.g., in prints, or on a projection screen or electronic display) are the same size, the smaller format has greater DOF.

Many small-format digital SLR camera systems allow using many of the same lenses on both full-frame and “cropped format” cameras. If the subject distance is adjusted to provide the same field of view at the subject, at the same f-number and final-image size, the smaller format has greater DOF, as with the “same picture” comparison above. If pictures are taken from the same distance using the same f-number, and the final images are the same size, the smaller format has less DOF. If pictures taken from the same subject distance are given the same enlargement, both final images will have the same DOF. The final images will, of course, have different sizes.

Cropping an image and enlarging to the same size final image as an uncropped image taken under the same conditions is equivalent to using a smaller format under the same conditions, so the cropped image has less DOF.

When focus is set to the hyperfocal distance, the DOF extends from half the hyperfocal distance to infinity, and the DOF is the largest possible for a given f-number.

The advent of digital technology in photography has provided additional means of controlling the extent of image sharpness; some methods allow extended DOF that would be impossible with traditional techniques, and some allow the DOF to be determined after the image is made.

Aperature

The aperture stop of a photographic lens can be adjusted to control the amount of light reaching the film or image sensor. In combination with variation of shutter speed, the aperture size will regulate the film's or image sensor's degree of exposure to light. Typically, a fast shutter speed will require a larger aperture to ensure sufficient light exposure, and a slow shutter speed will require a smaller aperture to avoid excessive exposure.

Diagram of decreasing aperture sizes (increasing f-numbers) for "full stop" increments (factor of two aperture area per stop)

A device called a diaphragm usually serves as the aperture stop, and controls the aperture. The diaphragm functions much like the pupil of the eye – it controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. In general, the smaller the aperture (the larger the number), the greater the distance from the plane of focus the subject matter may be while still appearing in focus.

The lens aperture is usually specified as an f-number, the ratio of focal length to effective aperture diameter. A lens typically has a set of marked "f-stops" that the f-number can be set to. A lower f-number denotes a greater aperture opening which allows more light to reach the film or image sensor. The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity.

Aperture priority is a semi-automatic shooting mode used in cameras. It allows the photographer to choose an aperture setting and allow the camera to decide the shutter speed and sometimes ISO sensitivity for the correct exposure. This is sometimes referred to as Aperture Priority Auto Exposure, A mode, Av mode, or semi-auto mode.

Typical ranges of apertures used in photography are about f/2.8–f/22 or f/2–f/16,[4] covering 6 stops, which may be divided into wide, middle, and narrow of 2 stops each, roughly (using round numbers) f/2–f/4, f/4–f/8, and f/8–f/16 or (for a slower lens) f/2.8–f/5.6, f/5.6–f/11, and f/11–f/22. These are not sharp divisions, and ranges for specific lenses vary.

Rachel Clearly wrote an informative article on her blog "PhotogrphyTalk" describing the use of aperture to control depth of field.  Read Rachel's blog here.

Salon

In 1674, the royally sanctioned French institution of art patronage, the Académie royale de peinture et de sculpture (a division of the Académie des beaux-arts), held its first semi-public art exhibit at the Salon Carré. The Salon's original focus was the display of the work of recent graduates of the École des Beaux-Arts, which was created by Cardinal Mazarin, chief minister of France, in 1648. Exhibition at the Salon de Paris was essential for any artist to achieve success in France for at least the next 200 years. Exhibition in the Salon marked a sign of royal favor.

In 1725, the Salon was held in the Palace of the Louvre, when it became known as Salon or Salon de Paris. In 1737, the exhibitions became public and were held, at first, annually, and then biannually in odd number years. They would start on the feast day of St. Louis (25 August) and run for some weeks. Once made regular and public, the Salon's status was "never seriously in doubt" (Crow, 1987). In 1748 a jury was introduced. Its members were awarded artists. From this time Salon got its undisputed influence.

Source http://en.wikipedia.org/wiki/Salon_(Paris)

 

The current accepted use of word Salon is related to a photography competition.  Anyone interested in photography is invited to enter his/ her work for a salon.  The competition is judged, and a number of awards are awarded:

  • The Winner receives a national medal
  • The runner up image receives a club medal
  • The top 5% receives a certificate of merit
  • The top 20% receives an acceptance
It is considered quite an honor to receive a salon acceptance today.
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