EXPOSURE
Exposure is the amount of light collected by the sensor in your camera whilst taking a picture.
Over-exposure is when too much light has entered the sensor causing the image to appear washed out.
Under-exposure is when not enough light has reached the sensor causing the image to look too dark.
Over-exposure is when too much light has entered the sensor causing the image to appear washed out.
Under-exposure is when not enough light has reached the sensor causing the image to look too dark.
THE EXPOSURE TRIANGLE
The exposure triangle refers to the relationship between the ISO, Aperture and Shutter-speed, these three settings can be adjusted independently to control the exposure. Briefly explained, ISO is the cameras sensitivity to light, Aperture is the size of the hole in the cameras lens and the Shutter-speed is the speed at which the shutter moves.
A few metaphors to help you understand the relationship between ISO, Aperture and Shutter-speed better:
The Window Metaphor
Let's imagine that your camera is like a window with shutters that can open and close.
- The Aperture would relate to the size of the window
- The Shutter-speed os the amount of time that the shutters of the window are open
- The ISO is you in the room wearing a pair of sun-glasses, desensitising your eyes to the light
To increase the amount of light in the room (increase exposure) you could increase the size of the window (increase aperture) the the shutters open for longer (slower shutter-speed) or you could simply remove your sunglasses making your eyes more sensitive to the light (increase ISO).
The Sunbathing Metaphor
Now we'll imagine that exposure is like getting a tan!
- The Aperture this time is your suntan lotion which reduces the effects of the sun depending on the
lotions strength (the apertures f-stop)
- The Shutter-speed is the length of time you spend out in the sun
- The ISO is like your skin type, some people are more sensitive to the sun than others
To increase your chances of getting a suntan (increase exposure) you can use a lower strength lotion (larger aperture), spend more time out in the sun (slower shutter-speed), and those more sensitive to sunlight will feel the greatest effects (high ISO).
It is also important to note that changing each element not only impacts the exposure of the image but each one also has an impact on other aspects of the image (i.e. changing aperture also changes Depth of Field, altering the shutter-speed impacts how motion is captures and adjusting the ISO alters the graininess of the shot).
A few metaphors to help you understand the relationship between ISO, Aperture and Shutter-speed better:
The Window Metaphor
Let's imagine that your camera is like a window with shutters that can open and close.
- The Aperture would relate to the size of the window
- The Shutter-speed os the amount of time that the shutters of the window are open
- The ISO is you in the room wearing a pair of sun-glasses, desensitising your eyes to the light
To increase the amount of light in the room (increase exposure) you could increase the size of the window (increase aperture) the the shutters open for longer (slower shutter-speed) or you could simply remove your sunglasses making your eyes more sensitive to the light (increase ISO).
The Sunbathing Metaphor
Now we'll imagine that exposure is like getting a tan!
- The Aperture this time is your suntan lotion which reduces the effects of the sun depending on the
lotions strength (the apertures f-stop)
- The Shutter-speed is the length of time you spend out in the sun
- The ISO is like your skin type, some people are more sensitive to the sun than others
To increase your chances of getting a suntan (increase exposure) you can use a lower strength lotion (larger aperture), spend more time out in the sun (slower shutter-speed), and those more sensitive to sunlight will feel the greatest effects (high ISO).
It is also important to note that changing each element not only impacts the exposure of the image but each one also has an impact on other aspects of the image (i.e. changing aperture also changes Depth of Field, altering the shutter-speed impacts how motion is captures and adjusting the ISO alters the graininess of the shot).
SHUTTER-SPEED
Shutter-speed refers to the amount of time that the shutter of the camera is open. Shutter-speed is measured in seconds or fractions of seconds, the larger the number the faster the shutter is moving (e.g. 1/1000 is considerably faster than 1/25 therefore will let in less light). You will begin to see evidence of camera shake at shutter speeds 1/60 and slower, however, if the camera is hand held, ideally you should use a tripod if using such slow shutter-speeds. Some cameras also have inbuilt anti-shake or Image Stabilisation technology. To help keep your camera steady whilst taking a picture at a very slow shutter-speed you could also use a shutter release mechanism to set your camera on timer to prevent any sort of movement from the camera itself, this will aid to produce the sharpest pictures possible. You can capture intentional blur in order to portray movement within an image.
The slower the shutter-speed the more blur you capture, though there is also an increase of light entering the camera which risks over-exposure. You can compensate for this by increasing the f-stop, decreasing the ISO or a combination of the two.
The slower the shutter-speed the more blur you capture, though there is also an increase of light entering the camera which risks over-exposure. You can compensate for this by increasing the f-stop, decreasing the ISO or a combination of the two.
Panning is another example of capturing movement whilst using a slow shutter-speed, this is when you move your camera in time with the movement of a subject, getting a relatively sharp subject but blurring the background.
It's even possible to draw pictures while using a long exposure (2-30 seconds). With this shutter left open for long periods of time the camera will capture all light emitted in front of it. To the left is an image of a Dinosaur skull I drew using a torch in a dark room, the shutter-speed was set to 30 seconds.
In contrast you can freeze movement using a faster shutter-speed as demonstrated in the picture below of a droplet splashing down.
APERTURE (F-NUMBER)
The aperture refers to the size of the opening in the lens, the larger this hole is the more light that enters the camera. The size of the aperture is measured in 'f-stops' e.g. f/2.8, f/4, f/5.6, f/8 and so on... The smaller the f-number, the larger the aperture gets (e.g. f/2.8 is a very large aperture size and f/32 is a very small aperture size - therefore f/2.8 will let in more light than f/32). The f-stop chosen also affects the Depth of Field (DoF). Depth of Field refers to the amount of your shot that will be in focus. A large DoF means that the majority of the image is in focus, a small (or shallow) DoF means that only a part of the image will be in focus, the rest for the image will be fuzzy. Larger apertures (smaller f-numbers) will produce images with a shallow DoF; smaller apertures (larger f-numbers) will give you a larger DoF.
If you are taking a picture and you wish to increase the DoF without changing the exposure, the solution is simple, when you increase the aperture by one stop, decrease the shutter-speed by one stop also. This will produce an image with a slightly different DoF and capture a moving object a little differently also, but will maintain exposure. Alternatively if you wish only to increase shutter-speed for example without altering the aperture you can adjust the ISO in order to attain correct exposure.
ISO
In digital photography, ISO is a measure of the cameras sensitivity to light. The higher the ISO the faster the camera collects light, however, you do also risk increased image noise when using a faster ISO. Ordinarily the ISO should be set low to achieve the best results when there is enough light, as lower ISO settings are less sensitive to light, producing finer grain (less image noise), though higher ISO settings can be particularly useful when shooting in dim light without the aid of a tripod. You can maintain a faster shutter-speed (e.g. when shooting indoor sporting events, a fast shutter-speed is required) therefore reduce the risk of blurring the image whilst maintaining correct exposure.
HIGH KEY
High key images are images that are intentionally over-exposed to create a bright and soothing picture. They tend to convey a more upbeat image if compared to low key images. They also generally lack contrast as well as a lack of shadows as the lighting needed to produce high hey images represses shadows. Light mades up most of a high key image with dark creating the detail.
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