The exposure triangle is a tool used by photographers to correctly expose the image using 3 different settings within the camera.
These settings are ISO, Aperture and Shutter Speed.
Each of these settings allow more or less light to hit the image sensor within the camera.
Now lets get in a little bit deeper what these different settings do to the image when you take the photo.
ISO stands for International Organization for Standardization and refers to how sensitive the image sensor is to light.
The lower the number, the less sensitive the image sensor is to the light and the higher the number, the more sensitive the image sensor is to the light.
The ISO also effects how much noise (grain) the image has when you take the photo.
The lower the ISO the less noise and the higher the ISO the more noise there is.
Noise is how much grain is in an image.
So if a higher ISO has more grain, why would I want to take the photo with a higher ISO?
There will be reasons why you would need a higher ISO when taking your photo from taking a photo in low light to wanting to be able to correctly expose your image while shooting with a faster shutter speed, and this brings me to…Shutter Speed
The shutter speed is how little or how much the image sensor is exposed to light and is taken in fractions of a second.
So if you shutter speed is set to 30, then that will mean the image sensor is exposed to 30 seconds of light and 1/1000 is 1000 of a second of light.
The reason for wanting to control our shutter speed is to create motion blur or to freeze your image. When it comes to the shutter speed, the longer the image sensor is exposed to the light the higher the chance of camera shake, when you take the photo without a tripod.
Camera shake is caused when small amount of movement causes the image to come out blurry.
This can be offset with the use of the reciprocal rule (a rule that gives you an idea of how slow you can go with your shutter speed before camera shake becomes noticeable).The Reciprocal Rule essentially states that the shutter speed needs to be at least the inverse of your focal length. Although it sounds a lot more complicated, it’s actually really simple.
For example, if you’re shooting with a 50mm lens, then your shutter speed should be at 1/50. If you’re shooting with a 100mm lens, then your shutter speed should be at least 1/100.
The law of average is that the slower the shutter speed the more photos you would have to take for one of the images coming out sharp.Aperture
The aperture is the opening in your lens and how wide the aperture opening is, the more light will come in to your camera.
Wider the aperture opening, the lower the F number and small the aperture opening, the higher the F number.
This is referred as the f-stop.
Remember lower f-stop number, the wider the aperture and higher the f-stop number, the smaller the aperture (This will take a bit of getting used to, but it does get easier the more you use it).A wider aperture (lower f-stop) means more of the foreground and background is out of focus while keeping the subject in focus. This is known as Bokeh (Japanese for Blurry).
A smaller aperture (higher f-stop) the more of the background and foreground is in focus with your subject.
In conclusion, the three different exposure methods will have different effect on the image and when combined in different ways will create a balanced exposed image that can freeze a moment or capture flowing movements.
The variety of settings can help focus on the scene or the subject and allow you to capture your subject in low light without the need of extra light source.