Task: Question Answering
Input (English): Context: A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph. Typically a light meter will include either digital or analog electronic circuit, which allows the photographer to determine which shutter speed and f-number should be selected for an optimum exposure, given a certain lighting situation and film speed., In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. A wide aperture admits uncollimated rays, resulting in a sharp focus only for rays coming from a certain distance. This means that a wide aperture results in an image that is sharp for things at the correct distance. The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). In the human eye, the pupil is the aperture., Aperture priority, often abbreviated A or Av (for aperture value) on a camera mode dial, is a setting on some cameras that allows the user to set a specific aperture value (f-number) while the camera selects a shutter speed to match it that will result in proper exposure based on the lighting conditions as measured by the camera's light meter. This is different from manual mode, where the user must decide both values, shutter priority where the user picks a shutter speed with the camera selecting an appropriate aperture, or program mode where the camera selects both., A lens mount is an interface  mechanical and often also electrical  between a photographic camera body and a lens. It is confined to cameras where the body allows interchangeable lenses, most usually the rangefinder camera, single lens reflex type or any movie camera of 16 mm or higher gauge. Lens mounts are also used to connect optical components in instrumentation that may not involve a camera, such as the modular components used in optical laboratory prototyping which join via C-mount or T-mount elements., A mode dial or camera dial is a dial used on digital cameras to change the camera's mode. Most digital cameras, including dSLR and SLR-like cameras, support modes, selectable either by a dial or from a menu. On point-and-shoot cameras which support modes a range of scene types is offered. On dSLR cameras and SLR-like cameras, mode dials usually offer access to manual settings. The more compact point-and-shoot cameras, and cameras offering a great many modes, do not have mode dials, using menus instead. Some SLR lenses themselves offer control over things such as aperture, reducing the need for mode support in the camera body., The Canon AV - 1 is a 35mm single - lens reflex camera with an FD lens mount , introduced by Canon Inc. in 1979 . The AV - 1 was very similar to the 1976 AE - 1 but provided aperture priority autoexposure rather than the AE - 1 's shutter speed priority AE . The camera is not capable of fully manual exposure . Canon 's international distributors , particularly in the United States , had clamored for such a camera because competing brands offered mostly aperture - priority cameras and some preferred it . The AV in the name referred to the type of autoexposure ; Av ( Aperture Value ) is a common abbreviation for aperture priority . When this camera appeared , a new range of FD lenses was introduced , featuring instant mounting / unmounting of the lens . This was called the New FD mount and did away with the older type of mounting ring which was fitted on to the rear of the lens and was awkward to use and needed two hands , to a newer , easier system whereby the user lined up the red dot on the lens , with the red dot on the camera and simply turned the whole lens clockwise until it clicked into place . All the other AE - 1 accessories fit the AV - 1 ., In photography, shutter speed or exposure time is the length of time when the film or digital sensor inside the camera is exposed to light, also when a camera's shutter is open when taking a photograph.
The amount of light that reaches the film or image sensor is proportional to the exposure time. 1/500th of a second will let half as much light in as 1/250th., A rangefinder camera is a camera fitted with a rangefinder, typically a split-image rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves when a calibrated wheel is turned; when the two images coincide and fuse into one, the distance can be read off the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the value to the lens focus ring; cameras without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was incorporated into the viewfinder. More modern designs have rangefinders coupled to the focusing mechanism, so that the lens is focused correctly when the rangefinder images fuse; compare with the focusing screen in non-autofocus SLRs., Shutter priority refers to a setting on some cameras that allows the user to choose a specific shutter speed while the camera adjusts the aperture to ensure correct exposure. This is different from manual mode, where the user must decide both values, aperture priority where the user picks an aperture with the camera selecting the shutter speed to match, or program mode where the camera selects both., , commonly known as TOPIX, along with the Nikkei 225, is an important stock market index for the Tokyo Stock Exchange (TSE) in Japan, tracking all domestic companies of the exchange's First Section. It is calculated and published by the TSE. , there are 1,669 companies listed on the First Section of the TSE, and the market value for the index was ¥197.4 trillion., The T-mount is a standard lens mount for cameras and other optical assemblies. The usual T-mount is a screw mount using a male 42×0.75 (42 mm diameter, 0.75 mm thread pitch) metric thread on the lens with a flange focal distance of 55 mm and a mating female 42mm thread on a camera adapter or other optical component. This thread form is referred to as T-thread. (This should not be confused with the M42 lens mount which is also 42 mm diameter, but has a 1 mm thread pitch.), The , which is called or TSE for short, is a stock exchange located in Tokyo, Japan. It is the fourth largest stock exchange in the world by aggregate market capitalization of its listed companies, and largest in East Asia and Asia. It had 2,292 listed companies with a combined market capitalization of US$4.09 trillion as of April 2015., The movie camera, film camera or cine-camera is a type of photographic camera which takes a rapid sequence of photographs on an image sensor or on a film. In contrast to a still camera, which captures a single snapshot at a time, the movie camera takes a series of images; each image constitutes 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 at a particular frame rate, a person's eyes and brain merge the separate pictures together to create the illusion of motion., The New York Stock Exchange (abbreviated as NYSE and nicknamed "The Big Board"), is an American stock exchange located at 11 Wall Street, Lower Manhattan, New York City, New York. It is by far the world's largest stock exchange by market capitalization of its listed companies at US$19.3 trillion as of June 2016. The average daily trading value was approximately 169 billion in 2013. The NYSE trading floor is located at 11 Wall Street and is composed of 21 rooms used for the facilitation of trading. A fifth trading room, located at 30 Broad Street, was closed in February 2007. The main building and the 11 Wall Street building were designated National Historic Landmarks in 1978., Canon has a primary listing on the Tokyo Stock Exchange and is a constituent of the TOPIX index. It has a secondary listing on the New York Stock Exchange. At the beginning of 2015, Canon was the tenth largest public company in Japan when measured by market capitalization., In optics, the f-number (sometimes called focal ratio, f-ratio, f-stop, or relative aperture) of an optical system is the ratio of the lens's focal length to the diameter of the entrance pupil. It is a dimensionless number that is a quantitative measure of lens speed, and an important concept in photography. The number is commonly notated using a hooked f, i.e. N, where N is the f-number., Subject: canon av-1, Relation: instance_of, Options: (A) 1 (B) april (C) brain (D) camera (E) canon (F) change (G) city (H) company (I) component (J) diameter (K) dimensionless number (L) distance (M) electronic circuit (N) exchange (O) index (P) instrumentation (Q) interface (R) june (S) laboratory (T) lens mount (U) lighting (V) market (W) meter (X) metric (Y) mode (Z) number ([) opening (\) person (]) photography (^) point (_) public company (`) range (a) rapid (b) ratio (c) ring (d) sequence (e) single (f) standard (g) still camera (h) stock exchange (i) thread (j) two (k) user (l) value (m) wall (n) will
Output (English): still camera