In this post we will discuss Aperture and its role in the Exposure Triangle. Aperture is the size of the hole that gathers light for your lens and the camera. The larger the hole, the more light can be gathered in a given amount of time. Just to be confusing, the larger the number, the smaller the hole. It makes more sense if you think of it as a fraction.
Another aspect of Aperture is in determining the Depth of Field (DOF) of the exposure.
You might want a shallow depth of field with a blurred background (called Bokeh) for a portrait of an individual where you want the focus of the picture to be on your subject, not the background.
Here is an example of a portrait shot with good bokeh of my son Griffin.
Here are a couple of examples.
All of these shots were taken at different Apertures from F/16 to F/1.8. So from these, we can learn that the smaller the Aperture number (which means the larger the “hole”) the shallower the Depth of Field. The blurry background you achieve with a shallow DOF is referred to as . Alternatively, the smaller the hole (larger Aperture number) the deeper the Depth of Field. The lens I used was a prime lens meaning it has only one focal distance (no zoom) so all of these were taken with an 85mm lens. (Full disclosure I have a DX frame camera, so the focal length is about 1.5 x 85mm, a topic for another post).
The above image was taken at an Aperture of F/16 (smaller hole) and has a fairly deep Depth of Field
The next image was taken at an aperture of F/4, a medium size hole with medium Depth of Field
The last image was taken at F/1.8 (large hole) and has a very shallow Depth of Field
So we discussed when you might want a shallow depth of field, when you have a single subject or subjects lined up at the same distance from the camera. You would want more depth of field if you were trying to shoot subjects that are not the same distance or a landscape shot. The important thing to remember is that all of these are guidelines, not rules. Feel free to deviate and see what your camera will do!
f/20 with some good depth of field.
Next we will look into Shutter Speed. If you find these posts interesting, please share them on Twitter or Facebook! Thanks!
Questions and comments welcome as always!