MTAL
25th February 2008, 03:52 PM
Just a few notes that will hopefully help someone!!!...
EXPOSURE AND LIGHT
SLR = Single Lens Reflex
EV = Exposure Value
AV = Aperture Value
TV = Time Value
ISO = Film Speed
Exposure is measuring and balancing of light. The photographer can control how much natural light reaches the film by adjusting the cameras shutter, aperture or film speed.
The moment of exposure
Most of the time the inside of the camera is totally dark. When a photograph is taken the camera opens and the light from outside floods in through the lens, lights is projected onto the film to make exposure.
Measuring light - technical exposure
A good technical exposure will produce a final image that accurately represents the original scene
Balancing light – artistic exposure
Just to make things interesting, in any situation there are several camera settings the give exactly the brightness but with very different outcomes.
Factors to gain the right exposure:
1. Light falling on the subject
2. Film speed (ISO)
3. Lens aperture
4. Shutter speed
5. Filters used
• If the shot is exposed too long it will look washed out = overexposed
• If the shot is exposed too short it will be too dark = underexposed
ISO
ISO rating describes how quickly the film reacts to light.
You can change the sensitivity of the sensor when collecting light; this is called the ISO speed.
The common span of ISO speed is 100 to 800 the higher the ISO speed the faster the camera collects lights but it also adds more noise to the photograph than the lower speeds, for example if you are trying to take pictures in a dim light without a tripod you might want to raise the ISO speed in order to get a picture that is not blurry.
Most of the time you should keep a low ISO speed if there is enough light, but it makes a big difference when there isn’t.
Film speed used stops just like shutter speed and aperture, for example going from ISO50 to ISO200 buys you 2 stops more light.
The trade-off between low and high ISO is quality, low ISO generally produce sharper, more detailed images, while higher ISO often has more contrast and noise.
CONTROLLING EXPOSURE
In order for an image to be captured on film it must be exposed to light. The camera had two settings to control light and they work very similar to the human eye.
The Shutter
The shutter blocks all from exposing the film until you press the button, then it quickly opens and closes giving the film a brief flash of light
Shutter Speed
To control the amount of time the shutter stays open
Longer shutter speed = more light
Shorter shutter speed = less light
Amount of time the sensor is exposed to light
Used to freeze or blur subjects
THE APERTURE
Before light reaches film it must pass through an opening called an “aperture”. The aperture is like a pupil, you can control the aperture by setting the “Aperture Opening” known as an F-Stop.
Smaller F-stops numbers = larger openings = more light
Larger F-stops = smaller opening = less light
The Size of the opening that lets light into the camera
Controls the depth of field what is in focus and what isn’t
• Blurred background = wide aperture = low f-stop
• Everything in focus = narrow aperture = high f-stop
Like the pupil in a human eye the aperture on a camera controls light, it does so by closing up to restrict light and opening to let it through.
BALACING SHUTTER AND APERTURE
Exposure is about different combinations of shutter speed and f-stop settings. These combinations can drastically affect the finished picture.
Take a stop, give a stop:
Since f-stop and shutter are both measured in stops keeping the balance is easy, if you take away 2 stops from the aperture you can give two stops back with the shutter and end up with the same exposure level.
AN EXAPMLE
If you are photographing a parade and your light meter indicates a proper exposure of 1/125 at f11. But, you want to use a faster shutter speed to freeze the action of those marching past and decide that 1/250 would be more appropriate.
Changing from one shutter speed to another which is twice as fast (1/125 to 1/250) allows half as much light to strike the film and therefore your picture would be underexposed, but if you open up the aperture by one stop it will allow twice as much light to come in and you will have proper exposure again.
The faster shutter speed reduced the light striking the film by 50% but changing to a wider aperture compensate for this reduction by doubling the amount of light, thereby preserving the proper exposure.
In this example both 1/125 at f11 and 1/250 at f8 will give proper exposure but the exposure with faster shutter speed as more action-stopping ability.
TIPS
A brightly lit scene can be correctly photographed by closing the aperture and using a faster shutter speed
When you come inside to a dark place after being in a bright place your iris opens out and vice versa, a camera needs to do the same… the aperture being the iris
Remember that shutter speed, f-stop settings and even film speed are all rated in units of “stops”
If you decrease a stop in shutter speed you must add a stop in aperture and vice versa
1/125 f5.6 ISO 100 is as bright as:
1/250 f4 ISO 100 is as bright as:
1/500 f4 ISO 200
EXPOSURE AND LIGHT
SLR = Single Lens Reflex
EV = Exposure Value
AV = Aperture Value
TV = Time Value
ISO = Film Speed
Exposure is measuring and balancing of light. The photographer can control how much natural light reaches the film by adjusting the cameras shutter, aperture or film speed.
The moment of exposure
Most of the time the inside of the camera is totally dark. When a photograph is taken the camera opens and the light from outside floods in through the lens, lights is projected onto the film to make exposure.
Measuring light - technical exposure
A good technical exposure will produce a final image that accurately represents the original scene
Balancing light – artistic exposure
Just to make things interesting, in any situation there are several camera settings the give exactly the brightness but with very different outcomes.
Factors to gain the right exposure:
1. Light falling on the subject
2. Film speed (ISO)
3. Lens aperture
4. Shutter speed
5. Filters used
• If the shot is exposed too long it will look washed out = overexposed
• If the shot is exposed too short it will be too dark = underexposed
ISO
ISO rating describes how quickly the film reacts to light.
You can change the sensitivity of the sensor when collecting light; this is called the ISO speed.
The common span of ISO speed is 100 to 800 the higher the ISO speed the faster the camera collects lights but it also adds more noise to the photograph than the lower speeds, for example if you are trying to take pictures in a dim light without a tripod you might want to raise the ISO speed in order to get a picture that is not blurry.
Most of the time you should keep a low ISO speed if there is enough light, but it makes a big difference when there isn’t.
Film speed used stops just like shutter speed and aperture, for example going from ISO50 to ISO200 buys you 2 stops more light.
The trade-off between low and high ISO is quality, low ISO generally produce sharper, more detailed images, while higher ISO often has more contrast and noise.
CONTROLLING EXPOSURE
In order for an image to be captured on film it must be exposed to light. The camera had two settings to control light and they work very similar to the human eye.
The Shutter
The shutter blocks all from exposing the film until you press the button, then it quickly opens and closes giving the film a brief flash of light
Shutter Speed
To control the amount of time the shutter stays open
Longer shutter speed = more light
Shorter shutter speed = less light
Amount of time the sensor is exposed to light
Used to freeze or blur subjects
THE APERTURE
Before light reaches film it must pass through an opening called an “aperture”. The aperture is like a pupil, you can control the aperture by setting the “Aperture Opening” known as an F-Stop.
Smaller F-stops numbers = larger openings = more light
Larger F-stops = smaller opening = less light
The Size of the opening that lets light into the camera
Controls the depth of field what is in focus and what isn’t
• Blurred background = wide aperture = low f-stop
• Everything in focus = narrow aperture = high f-stop
Like the pupil in a human eye the aperture on a camera controls light, it does so by closing up to restrict light and opening to let it through.
BALACING SHUTTER AND APERTURE
Exposure is about different combinations of shutter speed and f-stop settings. These combinations can drastically affect the finished picture.
Take a stop, give a stop:
Since f-stop and shutter are both measured in stops keeping the balance is easy, if you take away 2 stops from the aperture you can give two stops back with the shutter and end up with the same exposure level.
AN EXAPMLE
If you are photographing a parade and your light meter indicates a proper exposure of 1/125 at f11. But, you want to use a faster shutter speed to freeze the action of those marching past and decide that 1/250 would be more appropriate.
Changing from one shutter speed to another which is twice as fast (1/125 to 1/250) allows half as much light to strike the film and therefore your picture would be underexposed, but if you open up the aperture by one stop it will allow twice as much light to come in and you will have proper exposure again.
The faster shutter speed reduced the light striking the film by 50% but changing to a wider aperture compensate for this reduction by doubling the amount of light, thereby preserving the proper exposure.
In this example both 1/125 at f11 and 1/250 at f8 will give proper exposure but the exposure with faster shutter speed as more action-stopping ability.
TIPS
A brightly lit scene can be correctly photographed by closing the aperture and using a faster shutter speed
When you come inside to a dark place after being in a bright place your iris opens out and vice versa, a camera needs to do the same… the aperture being the iris
Remember that shutter speed, f-stop settings and even film speed are all rated in units of “stops”
If you decrease a stop in shutter speed you must add a stop in aperture and vice versa
1/125 f5.6 ISO 100 is as bright as:
1/250 f4 ISO 100 is as bright as:
1/500 f4 ISO 200