The exposure triangle is simply the name for the 3 settings used to give exposure to a photograph. Exposure simply means collecting the correct quantity of light so that the photo is not to dark (under-exposed) or to light (over-exposed)
Exposure is determined by these 3 variables for each photo you take.
- shutter speed - controls the length of time to collect the correct quantity of light
- aperture - controls the depth of field or focus through the opening in the lens
- ISO - controls the amount of grain or digital noise on the photo
When teaching beginners photography courses I have found that it has been helpful to demonstrate these 3 settings with something visual rather than just a technical explanation.
The following 3 online apps are great for demonstrating how exposure works and how each one of the variables above can affect the resulting photograph. I hope you enjoy these apps and they help clarify things for you.
Book yourself onto the beginners course to learn even more about getting the best exposure possible from every shot with a better understanding of dynamic range, the histogram, metering and RAW vs Jpg format.