Learning About Exposure – A Short Explanation
There is no photography course that does not address Exposure. Exposure is how much light gets to the camera’s image sensor.
There are three scenarios that explain exposure:
- Not enough light – your picture is underexposed.
- Too much light – you picture is overexposed.
- The right amount of light – your picture is correctly exposed.
Without question, you want to be able to identify with scenario #3 every time.
If you sign up for almost any photography course, expect to have dreams, maybe even nightmares, about exposure. It is that important. Especially if you want to get the camera off the auto button.
Now, you don’t need to know all the science of light and exposure to get better at taking pictures, but you do need some basic knowledge.
There are three components to exposure. Each of these has a way to control it on most digital cameras. They are:
- Aperture – the size of the opening in the lens that allows light in
- Shutter Speed – the amount of time the shutter is open to allow in the light
- ISO – the camera’s sensitivity to light
I heard this explanation about the relationship between the 3 components of exposure. It goes something like this.
A Mind-Map For Learning About Exposure
Imagine your are in a room with a single source of light – a window with shutters.
In this story, the size of the window is the aperture. Perhaps it is possible to hire a contractor to enlarge the window. That would let in more light.
The shutters around the window can open and close. The amount of time they are open before closing again is the shutter speed. The longer they are open, the more light comes into the window.
Now, picture yourself sitting in the room with a pair of sunglasses on. The room is looking a bit dark, so you remove the sunglasses. This makes your eyes more sensitive to the light. This is how ISO works.
Changing any one of the components changes how much light gets in to the room. This is exactly how your camera works. Changing the ISO or the shutter speed or the aperture affects the amount or quality of light that gets in.
Hopefully this illustration gives you a pretty good idea of how the three elements of exposure work. In future posts, we will discuss each of these in more detail.
If you are interested in learning more about exposure, there is a very talented photographer who has written in great detail about it. The book is Understanding Exposure, How to Shoot Great Photographs with Any Camera by Bryan Peterson. You can also find some excellent videos by Bryan at Adorama TV. (Click the links to access the book or the videos.)