Getting the right exposure on a camera is all about changing how much light hits the sensor, and our main way of doing that has remained unchanged since the dawn of photography, and that’s aperture.
The aperture on your camera exists within the lens and effects how much light comes through the lens and into the camera. This will do several things but its main function is
to make your image brighter or darker as needed, this is an important part of what we call the exposure triangle which we will cover in another video. We describe aperture in F stops, or sometimes T stops on cinema lenses. F stops refer to how wide your aperture is, a smaller number means a wider aperture which will let more light in. So the higher the number, the less light will be hitting your cameras sensor. Each lens has a maximum widest aperture which is a very important factor when choosing which lens to use. For example this 50mm prime lens has a maximum aperture of F1.2 whereas this zoom lens has a maximum aperture of F4. This means that this prime lens will be able to let in far more light than this one. Often lenses will have two F stops displayed on them, for example a lens might be a F3.5 to F5.6. This means that the maximum aperture will change as you zoom the lens. When your zoomed all the way in, you won’t be able to open your aperture as wide as you can when zoomed all the way out. So, a lower Fstop number will let in more light, and a higher one will let in less and we use this to change our exposure. But that’s not the only thing that the aperture will effect. The aperture that you use will have a direct impact on your depth of field. If you use a wider aperture and let in more light, that will mean that less of your image will be in focus, and the areas that aren’t in focus like the background behind me, will soften and blur more. We call those out of focus areas ‘Bokeh’ and so for example you might often hear camera operators saying that they prefer the Bokeh of one lens over another. So if you want to throw your background out of focus and isolate your subject, you would open up your aperture to a lower Fstop. For example here is a shot of me at F1.4, and here is the same shot at F8. See how the background is far more out of focus on the F1.4 shot. Normally this is a good thing as it focuses your attention on the subject and makes the whole shot more attractive. But it does have its downsides, for example if I take a small step forward you’ll see that in the shot at f8 I am still in focus, whereas in the shot at f1.4 I definitely am not.
So not only does changing the aperture affect how light or dark your exposure is, but it also changes your depth of field. Thanks for watching, If you want to see the rest of this series on camera basics make sure your subscribed to the channel. I hope that was helpful and if you have any questions at all just leave a comment below.