THE EXPOSURE TRIANGLE
Photographers measure their light in Stops.
This comes from turning the dial on a camera’s shutter speed.
Traditionally, one turn of the dial equals one Stop of light.
Newer cameras are sometimes capable of greater sensitivity and can turn less than one stop.
This is the time that the camera has to take the photograph.
With traditional Digital SLR cameras, this is the time that the shutter exposes the sensor to light.
With newer mirrorless cameras or mobile phones there is not always a shutter,
so it is the amount of time that data is captured from the sensor.
For constant lighting and natural light, a longer exposure (slower shutter speed) results in a brighter photograph.
Traditionally one turn on a camera dial equals one ‘Stop’ of light.
For studio flash there is a limit to how fast most flash heads will fire,
effectively limiting the shutter speed to that of that particular flash unit.
Older flash units often have a limit of 1/60th of a second.
Newer flash units commonly work at 1/200th of a second.
Many very new flash units can work much faster, up to 1/5,000th of a second,
This High Speed Synchronisation uses a lot more battery power and takes longer to recharge between photos.
This is the diameter that the lens aperture is opened and is measured in F stops.
Three F-Stops equals one ‘Full’ Stop.
One turn on the dial represents one third of a Stop.
With Traditional Digital SLR cameras the aperture can be opened and closed.
A more open lens allows more light in.
A more closed lens allows less light in.
With most professional lenses an aperture of F2.8 is the most it can open and F22 is as small it can go.
Kit lenses (provided as a bundle with a camera) usually open to F5.6 and close to F22.
Some prime lenses can open further to F1.2 allowing in a lot of light.
These tend to be more expensive and for niche use.
F2.8 will result in a brighter image and
F22 will result in a darker image.
ISO (Camera Sensitivity)
This is your camera’s sensitivity,
This used to be the sensitivity of the film that you put in your camera.
Traditionally (with film) an ISO of 100 would be considered ‘standard’,
with most new digital cameras, an ISO of 400-800 is considered a baseline standard.
With film, ISO 400 would have been used for overcast conditions & ISO 800 would for sports.
ISO 1600 would have been for very low light or very fast sports.
The trade off with a higher sensitivity setting is increased grain within your photograph.
This was true for film and is still true for digital cameras.
However, newer cameras can go to very very high ISO settings and still produce very good results.
Some photographers will also deliberately use a high sensitivity setting to create a retro looking photograph directly from the camera,
this can be particularly effective for black and white photography.
This can be very effective for street photography.
Some photographers prefer to have their grain directly from the camera, rather than adding it in during post production.
Camera Exposure Modes
Traditional Camera Modes
(Point and Shoot)
Essentially, does what it says on the button.
The camera works everything out for you and happily used by snappers around the world.
However, this quickly becomes limiting when you need to photograph something other than quick snaps or in less than a ‘default’ environment.
(A bit more control)
The camera takes control of your exposure settings.
It also allows you to override any of the settings by turning their dials.
The camera will automatically adjust the other settings.
(Fixed Lens Aperture)
The photographer selects an aperture and then the camera alters the other settings to obtain the correct exposure.
Very handy when you need to obtain a specific depth of field.
(Fixed Shutter Speed)
The photographer selects a specific shutter speed.
The camera alters the other settings to obtain the correct exposure.
Very handy when you wish to shoot sports action or moving subjects.
(Fixed Shutter, Aperture & ISO)
Photographer fixes the aperture and shutter controls, usually the ISO settings as well.
Often used in a studio flash environment or where the ambient light is consistent.
Photographers will use this to ensure that a series of images all have exactly the same exposure.
This ensures consistency and can greatly cut down small adjustments during the post production phase.
Handy Developments in exposure Control
These two controls are very commonly used by digital photographers for swift and easy adjustments to exposure.
These were not available for film photography but are now used by many photographers.
Most modern cameras have this option.
You can change the desired exposure level up and down (Plus and Minus) in third stop levels.
Very handy for when your camera’s automatic exposure level is not quite right.
Particularly handy when shooting towards the light and against a dark background.
You can use this to override any mode in nearly all modern digital cameras, including Manual Mode.
A very useful tool for when you need a fixed depth of field and fixed shutter speed, but your ambient light is changing swiftly.
All of the adjustments are made by the camera automatically altering the camera's sensitivity.
This is used a lot by sports photographers who may need a fast shutter speed and fixed depth of field.