Objective: Students will understand how aperture, shutter speed and ISO affect exposure.
What is exposure?
In the simplest terms, exposure is: “is the total amount of light allowed to fall on the photographic medium during the process of taking a photograph”
When you think of the craft or art of photography, you must immediately think of exposure. Exposure is a critical element that determines what is actually recorded on film or the image sensor.
When you think of the craft or art of photography, you must immediately think of exposure. Exposure is a critical element that determines what is actually recorded on film or the image sensor.
Too much light will "overexpose" your image, too little light will "underexpose"
What determines exposure?
The "Exposure Triangle"
1.) F-Stop (Aperture): The size of the opening that the light passes through
2.) Shutter Speed: The length of time that the sensor is exposed to light
3.) ISO: The sensitivity of the sensor
1.) F-Stop (Aperture): The size of the opening that the light passes through
2.) Shutter Speed: The length of time that the sensor is exposed to light
3.) ISO: The sensitivity of the sensor
Let's break it down...
f-stop (aperture)
Aperture is the hole through which light enters the camera. The size of the hole can be changed to control how much light is let into the camera. Smaller aperture= less light, Larger aperture= more light!
Think of it like your pupil. When its dark out, your pupils open very wide to let more light in to help you see better. When you are outside in the bright sun, your pupils get smaller, to block some of that light out!
The size of the aperture is referred to as an "f-stop." Larger f-stop numbers (like f/22) designate a smaller aperture. Smaller f-stop numbers (like f/2.8) designate a wider aperture. (Confusing, I know!)
Shutter speed also controls your "depth of field" or the area of your photo that is in focus. A small aperture (larger f-stop number) will keep most if not all of your image in clear focus. A wide aperture (smaller f-stop number) will keep only a certain area of your photo in focus, leaving elements outside of that area blurry.
Your f-stop controls:
- Exposure (how much light is let in to your camera)
- Depth of Field (the area of your photo that is in focus)
Think of it like your pupil. When its dark out, your pupils open very wide to let more light in to help you see better. When you are outside in the bright sun, your pupils get smaller, to block some of that light out!
The size of the aperture is referred to as an "f-stop." Larger f-stop numbers (like f/22) designate a smaller aperture. Smaller f-stop numbers (like f/2.8) designate a wider aperture. (Confusing, I know!)
Shutter speed also controls your "depth of field" or the area of your photo that is in focus. A small aperture (larger f-stop number) will keep most if not all of your image in clear focus. A wide aperture (smaller f-stop number) will keep only a certain area of your photo in focus, leaving elements outside of that area blurry.
Your f-stop controls:
- Exposure (how much light is let in to your camera)
- Depth of Field (the area of your photo that is in focus)
shutter speed
What is a shutter?.....A shutter is a device that allows light to pass for a determined period of time, for the purpose of exposing an electronic sensor to light to capture a permanent image of a scene.
"Shutter speed" then refers to the length of time that the shutter is open for. A slow shutter speed allows more time for light to enter- giving you more light. A faster shutter speed does not allow as much time to let light it- giving you less light.
If we were to use our eye example again, think of the shutter as your eye-lid. Shutter speed refers to how long your open your eyes for.
Shutter speed also controls how motion is captured. If you capture a moving subject with a fast shutter speed, it will freeze the action- giving you a crisp, clear image. If, however, you photograph that same moving subject with a slow shutter speed, your subject will appear blurry.
Shutter speed controls:
- Exposure (how much light is let in)
- how MOTION IS CAPTURED
"Shutter speed" then refers to the length of time that the shutter is open for. A slow shutter speed allows more time for light to enter- giving you more light. A faster shutter speed does not allow as much time to let light it- giving you less light.
If we were to use our eye example again, think of the shutter as your eye-lid. Shutter speed refers to how long your open your eyes for.
Shutter speed also controls how motion is captured. If you capture a moving subject with a fast shutter speed, it will freeze the action- giving you a crisp, clear image. If, however, you photograph that same moving subject with a slow shutter speed, your subject will appear blurry.
Shutter speed controls:
- Exposure (how much light is let in)
- how MOTION IS CAPTURED
ISO
The ISO setting makes the sensor (formerly film) more or less sensitive to light. The higher the ISO (3200), the more sensitive the camera is to light- which is useful when there is not much light around- like at night time.
However, the higher the ISO, the more "noise" there will be in your image. "Noise" refers to grainy specks that show up on your image. For this reason, it is best to always use the lowest ISO possible, as this will give you the best image quality. Usually this means an ISO of around 100.
ISO controls:
-Exposure (makes image sensor more or less sensitive to light)
-Image quality (the lower the ISO, the better the quality of your image)
However, the higher the ISO, the more "noise" there will be in your image. "Noise" refers to grainy specks that show up on your image. For this reason, it is best to always use the lowest ISO possible, as this will give you the best image quality. Usually this means an ISO of around 100.
ISO controls:
-Exposure (makes image sensor more or less sensitive to light)
-Image quality (the lower the ISO, the better the quality of your image)
Putting them all together...
When taking a photo, it is important that you consider all three parts of the exposure triangle (aperture, shutter speed and ISO) in order to get a correct exposure.
Each setting should balance each other out to achieve just the right amount of light.
For example:
Let's say you are photographing a sports game, where there are fast moving subjects. You know that you will need to set your shutter speed to a fast speed in order to freeze the action. However, faster shutter speeds let less light in, which could be a problem if there is not a lot of light available. To balance the fast shutter speed, you would then use a wide aperture (smaller f-stop) in order to allow more light into your camera.
Usually, you want to leave your ISO as low as possible (100) and only raise it if absolutely necessary.
Each setting should balance each other out to achieve just the right amount of light.
For example:
Let's say you are photographing a sports game, where there are fast moving subjects. You know that you will need to set your shutter speed to a fast speed in order to freeze the action. However, faster shutter speeds let less light in, which could be a problem if there is not a lot of light available. To balance the fast shutter speed, you would then use a wide aperture (smaller f-stop) in order to allow more light into your camera.
Usually, you want to leave your ISO as low as possible (100) and only raise it if absolutely necessary.
Here's a cheat sheet...
