Metering mode
Encyclopedia
In photography
, the metering mode refers to the way in which a camera
determines the exposure
.
Various metering modes are provided to allow the user to select the most appropriate one for use in a variety of lighting conditions.
, editor of The British Journal of Photography
in about 1935 and described it in the BJP Almanac of 1937 on pages 127 to 138.
A few models (including the Olympus OM-4
, Canon T90
and in the digital world, the Olympus C-5050z) support a Multi-Spot mode which allows multiple spot meter readings to be taken of a scene that are averaged. Some cameras, the OM-4 and T90 included, also support metering of highlight and shadow areas.
Spot metering is very accurate and is not influenced by other areas in the frame. It is commonly used to shoot very high contrast scenes. For example, if the subject's back is being hit by the rising sun and the face is a lot darker than the bright halo around the subject's back and hairline (the subject is "backlit"), spot metering allows the photographer to measure the light bouncing off the subject's face and expose properly for that, instead of the much brighter light around the hairline. The area around the back and hairline will then become over-exposed. Spot metering is a method upon which the Zone System
depends.
Another example of spot metering usage would be when photographing the moon. Due to the very dark nature of the scene, other metering methods tend to overexpose the moon. Spot metering will allow for more detail to be brought out in the moon while underexposing the rest of the scene.
, where it was called Automatic Multi-Pattern metering. On a number of cameras this is the default/standard metering setting. Here the camera measures the light intensity in several points in the scene, and then combines the results to find the settings for the best exposure. How they are combined/calculated deviates from camera to camera. The actual number of zones used varies wildly, from several to over a thousand. However performance should not be concluded on the number of zones alone, or the layout. In general, the most advanced metering is found on single-lens reflex cameras.
Many manufacturers are less than open about the exact calculations used to determine the exposure. A number of factors are taken into consideration, including the following:
Autofocus
point, distance to subject, areas in focus or out of focus, colours/hues of the scene, and backlighting. Multi-zone tends to bias its exposure towards the autofocus point being used (whilst taking into account other areas of the frame too), thus ensuring that the point of interest has been exposed for properly, (this often means the subject area being exposed for as a mid-tone). A database of many thousands of exposures is pre-stored in the camera, and the processor can use a selective pattern to determine what is being photographed.
Some cameras allow the user to link or unlink the autofocus and metering, and allow the option of locking exposure once AF confirmation is achieved, AEL, (auto-exposure lock). Using manual focus, and on many compacts/bridge cameras, the AF point is not used as part of the exposure calculation, in such instances it is common for the metering to default to a central point in the viewfinder, using a pattern based on that area. There is considerable variation from different manufacturers as to how multi-zone metering is implemented, and even from the same maker in their model range, and how much "priority" is given to the AF point itself. Some "Scene" modes, such as sunset, sports, night exposures etc., also often affect the calculations of this metering pattern.
However, some photographers may be uncomfortable with multi-zone metering. This tends to stem from a lack of clarity about "how" the camera reacts in certain situations. The design concept behind multi-zone is to reduce the need to use exposure compensation
.
Some users have problems making wide-angle shots with high contrast, due to the large area which can vary greatly in brightness. It is important to understand that even in this situation, the focus point can be critical to the overall exposure.
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
, the metering mode refers to the way in which a camera
Camera
A camera is a device that records and stores images. These images may be still photographs or moving images such as videos or movies. The term camera comes from the camera obscura , an early mechanism for projecting images...
determines the exposure
Exposure (photography)
In photography, exposure is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value and scene luminance over a specified area.In photographic jargon, an exposure...
.
Examples of metering modes
Cameras generally allow the user to select between spot, center-weighted average, or multi-zone metering modes.Various metering modes are provided to allow the user to select the most appropriate one for use in a variety of lighting conditions.
Spot metering
With spot metering, the camera will only measure a very small area of the scene (between 1-5% of the viewfinder area). This will typically be the very centre of the scene, but some cameras allow the user to select a different off-centre spot, or to recompose by moving the camera after metering. The first spot meter was built by Arthur James DalladayArthur James Dalladay
Arthur James Dalladay born December 1894 in West Ham, Essex. Died 1989 in Gravesend, Kent. Dalladay was the editor of the "British Journal Photographic Almanac & Photographer's Daily Companion" for 30 years from around 1937 to 1967....
, editor of The British Journal of Photography
British Journal of Photography
The British Journal of Photography is a magazine about photography publishing in-depth articles, profiles of photographs, analyses, and techological reviews.-History:...
in about 1935 and described it in the BJP Almanac of 1937 on pages 127 to 138.
A few models (including the Olympus OM-4
Olympus OM-4
The Olympus OM-4 is an interchangeable lens, 35 mm film, single lens reflex camera; manufactured by Olympus Optical Co., Ltd. in Japan and sold as OM-4 from 1983 to 1987 and as OM-4Ti from 1986 to 2002....
, Canon T90
Canon T90
The Canon T90, introduced in 1986, was the top of the line in Canon's T series of 35 mm Single-lens reflex cameras. It was the last professional-level manual-focus camera from Canon, and the last professional camera to use the Canon FD lens mount...
and in the digital world, the Olympus C-5050z) support a Multi-Spot mode which allows multiple spot meter readings to be taken of a scene that are averaged. Some cameras, the OM-4 and T90 included, also support metering of highlight and shadow areas.
Spot metering is very accurate and is not influenced by other areas in the frame. It is commonly used to shoot very high contrast scenes. For example, if the subject's back is being hit by the rising sun and the face is a lot darker than the bright halo around the subject's back and hairline (the subject is "backlit"), spot metering allows the photographer to measure the light bouncing off the subject's face and expose properly for that, instead of the much brighter light around the hairline. The area around the back and hairline will then become over-exposed. Spot metering is a method upon which the Zone System
Zone system
The Zone System is a photographic technique for determining optimal film exposure and development, formulated by Ansel Adams and Fred Archer. Adams described how the Zone System was developed: "I take this opportunity to restate that the Zone System is not an invention of mine; it is a codification...
depends.
Another example of spot metering usage would be when photographing the moon. Due to the very dark nature of the scene, other metering methods tend to overexpose the moon. Spot metering will allow for more detail to be brought out in the moon while underexposing the rest of the scene.
Center-weighted average metering
In this system, the meter concentrates between 60 to 80 percent of the sensitivity towards the central part of the viewfinder. The balance is then "feathered" out towards the edges. Some cameras will allow the user to adjust the weight/balance of the central portion to the peripheral one. One advantage of this method is that it is less influenced by small areas that vary greatly in brightness at the edges of the viewfinder; as many subjects are in the central part of the frame, consistent results can be obtained.Average metering
In this metering mode the camera will use the light information coming from the entire scene and averages for the final exposure setting, giving no weighting to any particular portion of the metered area.Partial metering
This mode meters a larger area than spot metering (around 10-15% of the entire frame), and is generally used when very bright or very dark areas on the edges of the frame would otherwise influence the metering unduly. Like spot metering, some cameras can use variable points to take readings from, (in general autofocus points), or have a fixed point in the centre of the viewfinder. Partial metering is found mostly on Canon cameras.Multi-zone metering
This mode is also called matrix, evaluative, honeycomb, segment metering, or esp (electro selective pattern) metering on some cameras. This metering mode was first introduced by the Nikon FANikon FA
The Nikon FA was an advanced amateur level, interchangeable lens, 35 mm film, single-lens reflex camera. It was manufactured by the Japanese optics company Nippon Kogaku K. K. in Japan from 1983 to 1987...
, where it was called Automatic Multi-Pattern metering. On a number of cameras this is the default/standard metering setting. Here the camera measures the light intensity in several points in the scene, and then combines the results to find the settings for the best exposure. How they are combined/calculated deviates from camera to camera. The actual number of zones used varies wildly, from several to over a thousand. However performance should not be concluded on the number of zones alone, or the layout. In general, the most advanced metering is found on single-lens reflex cameras.
Many manufacturers are less than open about the exact calculations used to determine the exposure. A number of factors are taken into consideration, including the following:
Autofocus
Autofocus
An autofocus optical system uses a sensor, a control system and a motor to focus fully automatic or on a manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication...
point, distance to subject, areas in focus or out of focus, colours/hues of the scene, and backlighting. Multi-zone tends to bias its exposure towards the autofocus point being used (whilst taking into account other areas of the frame too), thus ensuring that the point of interest has been exposed for properly, (this often means the subject area being exposed for as a mid-tone). A database of many thousands of exposures is pre-stored in the camera, and the processor can use a selective pattern to determine what is being photographed.
Some cameras allow the user to link or unlink the autofocus and metering, and allow the option of locking exposure once AF confirmation is achieved, AEL, (auto-exposure lock). Using manual focus, and on many compacts/bridge cameras, the AF point is not used as part of the exposure calculation, in such instances it is common for the metering to default to a central point in the viewfinder, using a pattern based on that area. There is considerable variation from different manufacturers as to how multi-zone metering is implemented, and even from the same maker in their model range, and how much "priority" is given to the AF point itself. Some "Scene" modes, such as sunset, sports, night exposures etc., also often affect the calculations of this metering pattern.
However, some photographers may be uncomfortable with multi-zone metering. This tends to stem from a lack of clarity about "how" the camera reacts in certain situations. The design concept behind multi-zone is to reduce the need to use exposure compensation
Exposure compensation
Exposure compensation is a technique for adjusting the exposure indicated by a photographic exposure meter, in consideration of factors that may cause the indicated exposure to result in a less-than-optimal image. Factors considered may include unusual lighting distribution, variations within a...
.
Some users have problems making wide-angle shots with high contrast, due to the large area which can vary greatly in brightness. It is important to understand that even in this situation, the focus point can be critical to the overall exposure.
External links
- Metering in the Digital Photography Review glossary.