Photography is the art of manipulating light-precisely and delicately. Because even the slightest difference in exposure can make significant difference. Good photography is all about getting the right amount of light on the film. The aim of any photographer is to produce a perfect negative which can provide him a print having details both in shadows and highlights areas. An under- exposed photograph lacks detail in the areas corresponding to shadows on the other hand over-exposure causes the highlight to become flat and washed -out. Reversal materials have less latitude than negative films so for transparency there is only one correct exposure and deviation one stop higher or lower gives only acceptable results
LATITUDE
Latitude indicates the range of exposure over which a photographic emulsion yields an acceptable negative. Generally speaking faster the film and less the subject contrast the greater the latitude.. Very slow films and reversal material have practically no latitude . Modern high speed film on the other hand have an overall latitude of 8 stops for an average subject within which it will provide acceptable result. That is why Cheaper cameras having fixed aperture recommend high speed film so that they can take advantage of their greater latitude..
Photography is the art of manipulating light-precisely and delicately. Because even the slightest difference in exposure can make significant difference. Good photography is all about getting the right amount of light on the film. The aim of any photographer is to produce a perfect negative which can provide him a print having details both in shadows and highlights areas. An under- exposed photograph lacks detail in the areas corresponding to shadows on the other hand over-exposure causes the highlight to become flat and washed -out. Reversal materials have less latitude than negative films so for transparency there is only one correct exposure and deviation one stop higher or lower gives only acceptable results .
Calculation of proper exposure is always a nightmare for a amateur and sometimes confuses professionals too. In this article we are going to learn how can we always get a perfectly exposed negative/Transparency in every lighting situations .But before going in detail we will have first to know what is exposure analyze the factors which affect exposure
Exposure is the amount of light falling on the film. Exposure in the scientific sense is the product of the intensity of light and the time during which the light acts. Practically for a photographer it means the particular combination of lens aperture and shutter speed that must be chosen to produce a perfect negative because the size of aperture governs the amount of light falling upon the film and shutter speed controls the length of time during which the light affects the film. The aperture and shutter speed are set according to the light and the sensitivity of the film . The sensitivity of the film is known from its ASA speed and for a particular film is constant so let us know in brief about the two other variables Aperture and Shutter Speed.
APERTURE:
When light passes through a camera's lens, it must pass through an opening called an "Aperture". In plain English it's a hole that lets in more light when it's wide open and less when it's small. In essence the aperture is just like the pupil in the human eye. You can control the aperture by setting the "Aperture Opening", also known as an F-Stop.
Aperture is measured in f/stops as indicated in the series below:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45
These are actually fractions. They should actually be read as follows:
1/1, 1/1.4, 1/2, 1/2.8, 1/4, 1/5.6, 1/8, 1/11, 1/16, 1/22, 1/32, 1/45
Each progression represents half as much light (moving to the right) as the preceding number. But why do the numbers look so odd? These numbers actually represent the ratio of the focal length of the lens to the diameter of the lens diaphragm opening. That's why it's called an f(ocal)/number. The designation "f/4" means that the diameter of the aperture is 1/4 the focal length of the lens. The designation f/16 means that the diameter of the aperture is 1/16 of the focal length of the lens. f/2 on a 100 mm lens means that the diameter of the diaphragm opening is 100/2, or 50 mm. The reason we use the ratios instead of the actual surface area of the diaphragm opening is that the actual surface area would be quite different between lenses of different focal lengths. Photographers would have to memorize a series of numbers for each focal length lens they owned. Think about what you'd have to do with a zoom lens! Ratios allow us to use the same number series for all of our lenses irrespective of their focal length. f/2 on a 100 mm lens lets in exactly the same amount of light as f/2 on a 500 mm lens.
If we stop down or close the lens opening from one stop to the next higher number ,we cut in half the amount of light entering. By opening up one f-stop we double the amount of entering light .Thus f4 admits half as much light as f 2.8 twice as much as f5.6. We must remember one thing that smaller the number bigger the aperture because f no is a fraction.
SHUTTER:
Shutter is a mechanical device used to expose the film to light for an exact period of time. The faster the shutter speed the smaller the amount of light gets in. Shutter speed indicates how long the camera shutter remains open to let light onto the film. The number series for shutter speed is:
15, 8, 4, 2, 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000, 4000, 8000
These numbers are whole seconds or fractions of seconds. They aren't expressed on your shutter speed dial as fractions to save space, so they should read as below:
15, 8, 4, 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/8000
Again, each number moving to the right is half the value of the preceding number, and represents half as much light as the preceding number.
THE CALCULATION OF EXPOSURE:
As we have already learned that the exposure is controlled by the proper use of Aperture and Shutter Speed combination but when to use which combination ?By referring to the exposure table printed on the instruction leaflet provided with the film , we may find out that in certain lighting condition the film requires an exposure, say, 1/125 seconds at f8. We can adjust the camera to this setting and take a correctly exposed transparency.
The light level encountered in photography vary enormously, from bright tropical sunshine to weak moon light .If the exposure is to be sufficiently accurate some means of accurate measuring of this light level is required. The human eye can detect quite small changes in the level of light at the moment they occur similarly in photography for accurate quantitative assessment of light Photo Electrical Cells are used, and these virtually form the basis of all exposure meters. With an exposure meter, you can venture into a wide variety of lighting conditions and be confident that you would consistently get good results. Their objective of a exposure meter is to take the guesswork out from taking Photograph.
WHAT IS AN EXPOSURE METER?
Simply saying exposure meter is an electronic device, which measures brightness level of light. All exposure meters measure light and, therefore ,contain an photo cell .The older exposure meters used selenium cell, which required no battery to operate. But the Selenium meters are not very light sensitive so Later on, Cadmium Sulphide (CDS) Photo resistive Cells became popular. These cells use batteries and have good sensitivity at low light levels, but these cells have a demerit that these suffer from "memory Effect" i.e. these tends to remember past bright readings for a little longer time than necessary and give wrong reading in fast shooting so now, modern camera and in handheld meters CDS cells have been replaced by silicon or gallium Photo Diodes. They diodes are very sensitive and responsive. Some of them are too sensitive to infrared and ultra violet, which is not used for normal photography so a blue filter is put on the photo diodes to compensate their red sensitivity. These diodes does not suffer from memory retention characteristic too. Exposure meters can be classified as two types:
A) INCIDENT LIGHT METERS
B) REFLECTED LIGHT METERS
INCIDENT LIGHT METERS :
It is also popularly known as Ambient Light Meter. This type of meter is very popular among Portrait Photographers and cinematographers. It measures the brightness of the source light falling on the subject.. Incident meter reading is taken from the subject position by pointing the exposure meter sensor towards the camera lens. This is because Incident meter measures the light falling on the subject coming from the direction of the camera. Incident meters are inherently more fool proof as it measures the intensity of light falling on the subject. So the subject color and brightness did not influence it. An Incident meter sensor is covered by a white translucent hemisphere, which acts as the proxy subject. The ambient light falls on the hemisphere from all angles up to 180 degree. So the meter accounts for most of the frontal lighting. The sensor measures the brightness of the illuminated hemisphere from inside and computes the incident light reading from it.
REFLECTED LIGHT METERS
This type of meter is found in all cameras having built in light meter. A reflected light meter takes the reading from the camera position pointing the exposure meter sensor towards the subject. This is the most common method of exposure evaluation. The cell of the meter is pointed towards the subject from roughly the same direction as the camera, and a reading is taken of the light reflected from the subject .All reflected type exposure meters are calibrated with one presumption that all subjects are medium gray in color. In logarithmic scale[]of brightness the middle point between pure black and white is 18% gray (approximately). Such reading works fine as long as the subjects are all near middle gray in brightness like green grass or human skin. Problem occurs when we try to photograph brighter or darker subjects. The reflected type exposure meter computes a reading by considering the subject as middle gray, which renders the brighter or darker subjects as middle gray.
BUILT-IN EXPOSURE METER
Almost all 35 mm camera and many medium format cameras are equipped with a reflective meter. In many modern cameras you may find more than one type of metering system to handle different type of lighting situation effectively you may switch between different metering systems.
CENTER WEIGHTED EXPOSURE METER
This type of meter sensor measures brightness from a wide area of the frame with an emphasis at the central part of the frame. Generally Camera bodies employ 75/25 ratio center weighted meter. Such a meter provides 75% weight to the brightness of the center of the frame and 25% weight to the rest part of the frame. Such design has evolved on the assumption that the key attraction of the frame is most likely to be placed at the center of the screen. The reading from a center weighted meter will be more accurate for the object at the center of the frame than an off center object.
MATRIX OR SEGMENTED METER
A single sensor cannot provide good reflective reading for a complex lighting situation. In a matrix meter, a number of sensors samples brightness from various areas of the frame and then the camera microprocessor compares the results with many of pre-fed exposure scenarios to provide a result, which is more accurate in most of the tricky light and backlit situation. Different manufactures call their Multi Pattern metering system by different names but they perform the same job. Every manufacturer has its own sophisticated algorithm, which may also take account of focus data, contrast between various sensor and analyze them with fuzzy logic algorithm so that it can analyze any lighting condition- as close as possible to the way the photographer sees. Canon named this mode of metering as Evaluative metering. Nikon calls it 3D colour Matrix metering it also analyses the scene colour Minolta uses a 14 segment honeycomb metering system, Pentax call its system 8 segment multi pattern metering. Olympus has a long name Digital Electro-Selective Pattern or Digital ESP metering and so on. This is the most sophisticated reflective metering available today to tackle most of the average and some tricky lighting situation. For photojournalists and sports photographer, where the photographer does not have time to think about exposure, it is the best exposure meter.
SPOT METER
There are times when you want more control of metering .The Spot meter measures brightness only from a tiny spot marked on the viewfinder. It does not care about the rest part of the scene. This is the meter of choice of most professional photographer. It provides the photographer to selectively sample the most important part of the scene and determine the correct exposure. This is undoubtedly the most powerful reflected meter mode for any knowledgeable photographer. The system usually employs a single cell positioned so that it takes a reading from only a small sharply defined area in the center of the focusing screen.. the screen is usually marked in some way to indicate the user the precise measuring area. Unfortunately not all consumer cameras provide this mode. Do check you camera manual to find out if your camera has this mode.
WHY YOUR LIGHT METER LIES TO YOU
Light meters can be less accurate than you might imagine. Their response to various colors of light may not match that of your film. Their response in low light and high light conditions may not match response at the mid-range of light. But the worst characteristic, for practical purposes, is that most of the reflected light meters make one basic (erroneous) assumption. They are calibrated to render an exposure that will make the subject look like a middle tone in the resulting photograph. So you must make exposure compensation when you photograph a light or dark toned subject than average. Use a meter reading as a guideline rather than a dictate for correct exposure. This makes it important that you understand how your particular meter works so you can consistently get good results no matter what is the lighting. The place to begin this understanding is the instruction manual that came with your meter or camera. The instructions should familiarize you with the meter's specific features, its flexibility, and its limitations. Most camera and exposure meter instructions provide the basic techniques of light measurement and mention some of the situations that may "fool" the meter.
HOW TO COMPENSATION EXPOSURE
Using the exposure compensation dial on your camera is useful when the area that you are metering off, is consistently darker or lighter than "average". How do you compensate for the fact that your meter is lying? You have to lie to your meter. If you are photographing a light toned subject, such as snow or sand in bright light, you must convince your meter that it is looking at something even lighter than your subject, so that the meter's attempt to make it a middle tone will result in the right tone. The same is true for dark objects. You must tell your meter that the object is darker than it really is so that the meter's compensation will register the correct tone in the photograph.
You can get a correct exposure in a couple of ways. You can meter a middle-toned area in the same light as your subject and manually set your camera accordingly. You can lie to the camera outright by telling it that it is using film of an ISO rating different from what is actually in the camera. For instance, if you are using ISO 100 film and are photographing a light subject, you would tell the meter that you have ISO 50 film. If you are photographing a dark object, tell your meter that you have ISO 200 film in the camera. This method works well for cameras in automatic exposure modes. Be careful to change the ASA speed to its original position when you move to a middle toned subject.
Another way to get the right exposure from a lying meter is to ignore it. Switch from automatic to manual exposure and simply move to the next larger aperture or the next slower shutter speed (for a light object) or to the next smaller aperture or faster shutter speed (for a dark object).
You can also use the exposure compensation dial of your camera for this if your camera have it.
HOW TO CHECK YOUR EXPOSURE METER AND CAMERA
If your results are consistently too light or too dark, your meter may be providing erroneous readings because of age, extensive use, or malfunction. The first thing to suspect, when a meter fails or readings become erratic, is the battery. you should replace batteries at least once a year. Cold weather is particularly hard on batteries, so if you're shooting in winter, carry backup batteries in a warm inside pocket where they'll retain their charge. If new batteries don't cure the problem, have your camera or meter checked by a professional repair technician or by the manufacturer.
HOW TO CHECK YOUR METER YOURSELF
To check the accuracy of your meter, you can compare its readings with a guide such as the daylight exposure table found inside a film carton. On a sunny day, aim your camera meter at front lighted, average subject. The exposure indicated by the meter should match the film carton recommendation within a 1/2 stop. For example, the suggested exposure for 100 ASA Film is 1/125 at f/16 or an equivalent shutter-aperture combination. It is also called f/16 rule or rule of thumb. If your meter indicates another setting, it may need repair or adjustment. If your meter indicates the correct exposure but your pictures are still too light or too dark, then your camera's shutter or lens aperture may be at fault.
METERING TECHNIQUES WITH REFLECTED LIGHT METERS
The various techniques describe below is applicable for any reflective meter including your in-camera exposure meter. In difficult light situation you should try any one of these for getting correct exposure
GREY CARD TECHNIQUE
This technique effectively turns any reflective meter (including your Camera in-build meter) into an Incident meter. It is used to determine very accurate exposure for a highkey, lowkey or high contrast subjects. For this technique, you will need a gray card. You may buy them from your local photo store. They come in different sizes and materials. Any one will serve the purpose. The technique of taking a Gray Card reading is as follows:
Set your camera into manual mode.
Place the gray card in front of your subject. If your subject is a human model, you can request him or her to hold it at chest height.
If the subject is side lit, then tilt the card to catch the sidelight.
Zoom it or walk to fill your camera frame only with the gray area of the card. Take care not to project your shadow on the gray card.
Meter the gray card
Remove the card, recompose and use the exposure reading to take the photograph.
The concept of gray card reading is simple; we are replacing our subject with a middle gray card, which has the reflectance as expected by any in-camera meter. The reading will be most accurate and independent of the subject and background, just like as an Incident Light meter.
READING FROM THE BACK OF YOUR PALM
If your gray card is not handy while shooting, you can use your own palm.. It is lighter than medium gray, so take the reading from your palm and then open up +1 stop (experiment to find your own setting). This will be your palm reading exposure. The colour of palm is generally constant but for a lighter or darker palm compensate accordingly.
SPOT METERING TECHNIQUE
The key rules in spot metering are:
1. Determine the most important part of the composition.
2. Try to identify the medium gray area of that important part and take a spot reading from there.
You first need to train your eyes to identify medium gray reflectance in the scene. Few tips in this regard may help beginners to get started in spot metering.
For portraits, the reading should be taken from medium lighted skin areas.
For Landscape, look for medium lit green pasture and meter from the grass.
For snow or sand, a gray card technique will provide better result. Even then, bracket your exposure half stop on either side.
Typical under-exposed Scenes
Exposure correction direction
Contra-light or back light situations
Plus (+)
Dominant white or yellow areas /White background
Snow/Beach scenes /Water
Typical -over-exposed Scenes
Exposure correction direction
Scenes with dark green like a forest
Minus(-)
Dominant shadows
Dominant dark objects/ Dark Background/Sunset or Sunrise/Night scenes
EXPOSURE BRACKETING
Technique of ensuring optimum exposure by taking several identical pictures of the same subject at slightly different exposure setting is called bracketing. Bracketing is used in tricky, non average lighting situations. Sometimes exposure correction is pretty easy but setting the right amount is often difficult. Just take a example of a simple sunset - finding the exact setting requires some experience here and even then you may like to take some additional pictures with different exposures just to see which exposure shows the best mood. This can be done manually or a bit faster and more conveniently via auto exposure bracketing by the camera. "ABC" (Auto Bracketing Control), "AEB" (Auto Exposure Bracketing) is featured by many mid and upper class cameras. Usually you just need to activate this feature and set a certain shutter speed/aperture combination and your camera will automatically take 3 to 5 pictures with defined exposure variations.
LATITUDE
Latitude indicates the range of exposure over which a photographic emulsion yields an acceptable negative. Generally speaking faster the film and less the subject contrast the greater the latitude.. Very slow films and reversal material have practically no latitude . Modern high speed film on the other hand have an overall latitude of 8 stops for an average subject within which it will provide acceptable result. That is why Cheaper cameras having fixed aperture recommend high speed film so that they can take advantage of their greater latitude..
Photography is the art of manipulating light-precisely and delicately. Because even the slightest difference in exposure can make significant difference. Good photography is all about getting the right amount of light on the film. The aim of any photographer is to produce a perfect negative which can provide him a print having details both in shadows and highlights areas. An under- exposed photograph lacks detail in the areas corresponding to shadows on the other hand over-exposure causes the highlight to become flat and washed -out. Reversal materials have less latitude than negative films so for transparency there is only one correct exposure and deviation one stop higher or lower gives only acceptable results .
Calculation of proper exposure is always a nightmare for a amateur and sometimes confuses professionals too. In this article we are going to learn how can we always get a perfectly exposed negative/Transparency in every lighting situations .But before going in detail we will have first to know what is exposure analyze the factors which affect exposure
Exposure is the amount of light falling on the film. Exposure in the scientific sense is the product of the intensity of light and the time during which the light acts. Practically for a photographer it means the particular combination of lens aperture and shutter speed that must be chosen to produce a perfect negative because the size of aperture governs the amount of light falling upon the film and shutter speed controls the length of time during which the light affects the film. The aperture and shutter speed are set according to the light and the sensitivity of the film . The sensitivity of the film is known from its ASA speed and for a particular film is constant so let us know in brief about the two other variables Aperture and Shutter Speed.
APERTURE:
When light passes through a camera's lens, it must pass through an opening called an "Aperture". In plain English it's a hole that lets in more light when it's wide open and less when it's small. In essence the aperture is just like the pupil in the human eye. You can control the aperture by setting the "Aperture Opening", also known as an F-Stop.
Aperture is measured in f/stops as indicated in the series below:
1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45
These are actually fractions. They should actually be read as follows:
1/1, 1/1.4, 1/2, 1/2.8, 1/4, 1/5.6, 1/8, 1/11, 1/16, 1/22, 1/32, 1/45
Each progression represents half as much light (moving to the right) as the preceding number. But why do the numbers look so odd? These numbers actually represent the ratio of the focal length of the lens to the diameter of the lens diaphragm opening. That's why it's called an f(ocal)/number. The designation "f/4" means that the diameter of the aperture is 1/4 the focal length of the lens. The designation f/16 means that the diameter of the aperture is 1/16 of the focal length of the lens. f/2 on a 100 mm lens means that the diameter of the diaphragm opening is 100/2, or 50 mm. The reason we use the ratios instead of the actual surface area of the diaphragm opening is that the actual surface area would be quite different between lenses of different focal lengths. Photographers would have to memorize a series of numbers for each focal length lens they owned. Think about what you'd have to do with a zoom lens! Ratios allow us to use the same number series for all of our lenses irrespective of their focal length. f/2 on a 100 mm lens lets in exactly the same amount of light as f/2 on a 500 mm lens.
If we stop down or close the lens opening from one stop to the next higher number ,we cut in half the amount of light entering. By opening up one f-stop we double the amount of entering light .Thus f4 admits half as much light as f 2.8 twice as much as f5.6. We must remember one thing that smaller the number bigger the aperture because f no is a fraction.
SHUTTER:
Shutter is a mechanical device used to expose the film to light for an exact period of time. The faster the shutter speed the smaller the amount of light gets in. Shutter speed indicates how long the camera shutter remains open to let light onto the film. The number series for shutter speed is:
15, 8, 4, 2, 1, 2, 4, 8, 15, 30, 60, 125, 250, 500, 1000, 2000, 4000, 8000
These numbers are whole seconds or fractions of seconds. They aren't expressed on your shutter speed dial as fractions to save space, so they should read as below:
15, 8, 4, 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, 1/4000, 1/8000
Again, each number moving to the right is half the value of the preceding number, and represents half as much light as the preceding number.
THE CALCULATION OF EXPOSURE:
As we have already learned that the exposure is controlled by the proper use of Aperture and Shutter Speed combination but when to use which combination ?By referring to the exposure table printed on the instruction leaflet provided with the film , we may find out that in certain lighting condition the film requires an exposure, say, 1/125 seconds at f8. We can adjust the camera to this setting and take a correctly exposed transparency.
The light level encountered in photography vary enormously, from bright tropical sunshine to weak moon light .If the exposure is to be sufficiently accurate some means of accurate measuring of this light level is required. The human eye can detect quite small changes in the level of light at the moment they occur similarly in photography for accurate quantitative assessment of light Photo Electrical Cells are used, and these virtually form the basis of all exposure meters. With an exposure meter, you can venture into a wide variety of lighting conditions and be confident that you would consistently get good results. Their objective of a exposure meter is to take the guesswork out from taking Photograph.
WHAT IS AN EXPOSURE METER?
Simply saying exposure meter is an electronic device, which measures brightness level of light. All exposure meters measure light and, therefore ,contain an photo cell .The older exposure meters used selenium cell, which required no battery to operate. But the Selenium meters are not very light sensitive so Later on, Cadmium Sulphide (CDS) Photo resistive Cells became popular. These cells use batteries and have good sensitivity at low light levels, but these cells have a demerit that these suffer from "memory Effect" i.e. these tends to remember past bright readings for a little longer time than necessary and give wrong reading in fast shooting so now, modern camera and in handheld meters CDS cells have been replaced by silicon or gallium Photo Diodes. They diodes are very sensitive and responsive. Some of them are too sensitive to infrared and ultra violet, which is not used for normal photography so a blue filter is put on the photo diodes to compensate their red sensitivity. These diodes does not suffer from memory retention characteristic too. Exposure meters can be classified as two types:
A) INCIDENT LIGHT METERS
B) REFLECTED LIGHT METERS
INCIDENT LIGHT METERS :
It is also popularly known as Ambient Light Meter. This type of meter is very popular among Portrait Photographers and cinematographers. It measures the brightness of the source light falling on the subject.. Incident meter reading is taken from the subject position by pointing the exposure meter sensor towards the camera lens. This is because Incident meter measures the light falling on the subject coming from the direction of the camera. Incident meters are inherently more fool proof as it measures the intensity of light falling on the subject. So the subject color and brightness did not influence it. An Incident meter sensor is covered by a white translucent hemisphere, which acts as the proxy subject. The ambient light falls on the hemisphere from all angles up to 180 degree. So the meter accounts for most of the frontal lighting. The sensor measures the brightness of the illuminated hemisphere from inside and computes the incident light reading from it.
REFLECTED LIGHT METERS
This type of meter is found in all cameras having built in light meter. A reflected light meter takes the reading from the camera position pointing the exposure meter sensor towards the subject. This is the most common method of exposure evaluation. The cell of the meter is pointed towards the subject from roughly the same direction as the camera, and a reading is taken of the light reflected from the subject .All reflected type exposure meters are calibrated with one presumption that all subjects are medium gray in color. In logarithmic scale[]of brightness the middle point between pure black and white is 18% gray (approximately). Such reading works fine as long as the subjects are all near middle gray in brightness like green grass or human skin. Problem occurs when we try to photograph brighter or darker subjects. The reflected type exposure meter computes a reading by considering the subject as middle gray, which renders the brighter or darker subjects as middle gray.
BUILT-IN EXPOSURE METER
Almost all 35 mm camera and many medium format cameras are equipped with a reflective meter. In many modern cameras you may find more than one type of metering system to handle different type of lighting situation effectively you may switch between different metering systems.
CENTER WEIGHTED EXPOSURE METER
This type of meter sensor measures brightness from a wide area of the frame with an emphasis at the central part of the frame. Generally Camera bodies employ 75/25 ratio center weighted meter. Such a meter provides 75% weight to the brightness of the center of the frame and 25% weight to the rest part of the frame. Such design has evolved on the assumption that the key attraction of the frame is most likely to be placed at the center of the screen. The reading from a center weighted meter will be more accurate for the object at the center of the frame than an off center object.
MATRIX OR SEGMENTED METER
A single sensor cannot provide good reflective reading for a complex lighting situation. In a matrix meter, a number of sensors samples brightness from various areas of the frame and then the camera microprocessor compares the results with many of pre-fed exposure scenarios to provide a result, which is more accurate in most of the tricky light and backlit situation. Different manufactures call their Multi Pattern metering system by different names but they perform the same job. Every manufacturer has its own sophisticated algorithm, which may also take account of focus data, contrast between various sensor and analyze them with fuzzy logic algorithm so that it can analyze any lighting condition- as close as possible to the way the photographer sees. Canon named this mode of metering as Evaluative metering. Nikon calls it 3D colour Matrix metering it also analyses the scene colour Minolta uses a 14 segment honeycomb metering system, Pentax call its system 8 segment multi pattern metering. Olympus has a long name Digital Electro-Selective Pattern or Digital ESP metering and so on. This is the most sophisticated reflective metering available today to tackle most of the average and some tricky lighting situation. For photojournalists and sports photographer, where the photographer does not have time to think about exposure, it is the best exposure meter.
SPOT METER
There are times when you want more control of metering .The Spot meter measures brightness only from a tiny spot marked on the viewfinder. It does not care about the rest part of the scene. This is the meter of choice of most professional photographer. It provides the photographer to selectively sample the most important part of the scene and determine the correct exposure. This is undoubtedly the most powerful reflected meter mode for any knowledgeable photographer. The system usually employs a single cell positioned so that it takes a reading from only a small sharply defined area in the center of the focusing screen.. the screen is usually marked in some way to indicate the user the precise measuring area. Unfortunately not all consumer cameras provide this mode. Do check you camera manual to find out if your camera has this mode.
WHY YOUR LIGHT METER LIES TO YOU
Light meters can be less accurate than you might imagine. Their response to various colors of light may not match that of your film. Their response in low light and high light conditions may not match response at the mid-range of light. But the worst characteristic, for practical purposes, is that most of the reflected light meters make one basic (erroneous) assumption. They are calibrated to render an exposure that will make the subject look like a middle tone in the resulting photograph. So you must make exposure compensation when you photograph a light or dark toned subject than average. Use a meter reading as a guideline rather than a dictate for correct exposure. This makes it important that you understand how your particular meter works so you can consistently get good results no matter what is the lighting. The place to begin this understanding is the instruction manual that came with your meter or camera. The instructions should familiarize you with the meter's specific features, its flexibility, and its limitations. Most camera and exposure meter instructions provide the basic techniques of light measurement and mention some of the situations that may "fool" the meter.
HOW TO COMPENSATION EXPOSURE
Using the exposure compensation dial on your camera is useful when the area that you are metering off, is consistently darker or lighter than "average". How do you compensate for the fact that your meter is lying? You have to lie to your meter. If you are photographing a light toned subject, such as snow or sand in bright light, you must convince your meter that it is looking at something even lighter than your subject, so that the meter's attempt to make it a middle tone will result in the right tone. The same is true for dark objects. You must tell your meter that the object is darker than it really is so that the meter's compensation will register the correct tone in the photograph.
You can get a correct exposure in a couple of ways. You can meter a middle-toned area in the same light as your subject and manually set your camera accordingly. You can lie to the camera outright by telling it that it is using film of an ISO rating different from what is actually in the camera. For instance, if you are using ISO 100 film and are photographing a light subject, you would tell the meter that you have ISO 50 film. If you are photographing a dark object, tell your meter that you have ISO 200 film in the camera. This method works well for cameras in automatic exposure modes. Be careful to change the ASA speed to its original position when you move to a middle toned subject.
Another way to get the right exposure from a lying meter is to ignore it. Switch from automatic to manual exposure and simply move to the next larger aperture or the next slower shutter speed (for a light object) or to the next smaller aperture or faster shutter speed (for a dark object).
You can also use the exposure compensation dial of your camera for this if your camera have it.
HOW TO CHECK YOUR EXPOSURE METER AND CAMERA
If your results are consistently too light or too dark, your meter may be providing erroneous readings because of age, extensive use, or malfunction. The first thing to suspect, when a meter fails or readings become erratic, is the battery. you should replace batteries at least once a year. Cold weather is particularly hard on batteries, so if you're shooting in winter, carry backup batteries in a warm inside pocket where they'll retain their charge. If new batteries don't cure the problem, have your camera or meter checked by a professional repair technician or by the manufacturer.
HOW TO CHECK YOUR METER YOURSELF
To check the accuracy of your meter, you can compare its readings with a guide such as the daylight exposure table found inside a film carton. On a sunny day, aim your camera meter at front lighted, average subject. The exposure indicated by the meter should match the film carton recommendation within a 1/2 stop. For example, the suggested exposure for 100 ASA Film is 1/125 at f/16 or an equivalent shutter-aperture combination. It is also called f/16 rule or rule of thumb. If your meter indicates another setting, it may need repair or adjustment. If your meter indicates the correct exposure but your pictures are still too light or too dark, then your camera's shutter or lens aperture may be at fault.
METERING TECHNIQUES WITH REFLECTED LIGHT METERS
The various techniques describe below is applicable for any reflective meter including your in-camera exposure meter. In difficult light situation you should try any one of these for getting correct exposure
GREY CARD TECHNIQUE
This technique effectively turns any reflective meter (including your Camera in-build meter) into an Incident meter. It is used to determine very accurate exposure for a highkey, lowkey or high contrast subjects. For this technique, you will need a gray card. You may buy them from your local photo store. They come in different sizes and materials. Any one will serve the purpose. The technique of taking a Gray Card reading is as follows:
Set your camera into manual mode.
Place the gray card in front of your subject. If your subject is a human model, you can request him or her to hold it at chest height.
If the subject is side lit, then tilt the card to catch the sidelight.
Zoom it or walk to fill your camera frame only with the gray area of the card. Take care not to project your shadow on the gray card.
Meter the gray card
Remove the card, recompose and use the exposure reading to take the photograph.
The concept of gray card reading is simple; we are replacing our subject with a middle gray card, which has the reflectance as expected by any in-camera meter. The reading will be most accurate and independent of the subject and background, just like as an Incident Light meter.
READING FROM THE BACK OF YOUR PALM
If your gray card is not handy while shooting, you can use your own palm.. It is lighter than medium gray, so take the reading from your palm and then open up +1 stop (experiment to find your own setting). This will be your palm reading exposure. The colour of palm is generally constant but for a lighter or darker palm compensate accordingly.
SPOT METERING TECHNIQUE
The key rules in spot metering are:
1. Determine the most important part of the composition.
2. Try to identify the medium gray area of that important part and take a spot reading from there.
You first need to train your eyes to identify medium gray reflectance in the scene. Few tips in this regard may help beginners to get started in spot metering.
For portraits, the reading should be taken from medium lighted skin areas.
For Landscape, look for medium lit green pasture and meter from the grass.
For snow or sand, a gray card technique will provide better result. Even then, bracket your exposure half stop on either side.
Typical under-exposed Scenes
Exposure correction direction
Contra-light or back light situations
Plus (+)
Dominant white or yellow areas /White background
Snow/Beach scenes /Water
Typical -over-exposed Scenes
Exposure correction direction
Scenes with dark green like a forest
Minus(-)
Dominant shadows
Dominant dark objects/ Dark Background/Sunset or Sunrise/Night scenes
EXPOSURE BRACKETING
Technique of ensuring optimum exposure by taking several identical pictures of the same subject at slightly different exposure setting is called bracketing. Bracketing is used in tricky, non average lighting situations. Sometimes exposure correction is pretty easy but setting the right amount is often difficult. Just take a example of a simple sunset - finding the exact setting requires some experience here and even then you may like to take some additional pictures with different exposures just to see which exposure shows the best mood. This can be done manually or a bit faster and more conveniently via auto exposure bracketing by the camera. "ABC" (Auto Bracketing Control), "AEB" (Auto Exposure Bracketing) is featured by many mid and upper class cameras. Usually you just need to activate this feature and set a certain shutter speed/aperture combination and your camera will automatically take 3 to 5 pictures with defined exposure variations.
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