Photography terms can seem so complicating and daunting at first, but really it is very simple once it is broken down and explained. Medical terms, for example, seem like jibberish to an outsider. But one of the first things a medical student learns is how to dissect those terms; it all becomes clear once they learn how to do so. One of the very first things I learned as a photographer is how important the terms Depth of Field (or “DOF”), Aperture, and “F/stops” are and how much of an important role they play in our dreamy photos. So let’s get to dissecting!
First let’s learn the basics of Depth of Field (“DOF”). Depth of Field is the amount of subject matter that is in the foreground and background of your subject that appears to be in focus. For example, if a photographer wanted to photograph a single person in a crowd of people, they would use a “shallow depth of field” to make the surroundings and background blurred and make the single subject the focus of the image. If, for instance, someone wanted to photograph a mountain landscape scene, wanting to capture all the details and textures, they would use a deeper depth of field.
There are 3 main things that affect Depth of Field:
The Aperture or “F/stop”
The Focal Length
The distance from your subject
With this article, I will touch base on “F/stops” specifically on how aperture works on a camera. I will discuss the other two in later articles. Be sure to subscribe to our newsletters so you don’t miss out! Aperture is one of two ways to control exposure on a camera (the other way being shutter speed). The aperture works in conjunction with the shutter speed in that the shutter speed controls the speed at which the light is let into the camera and the aperture is how wide the opening is that the light comes through. The lower the number or “F/stop” is, the wider the aperture opening is, and the shallower the DOF is. When your aperture number is higher, it means that the opening that the light is coming through is physically smaller and more of the image will be in focus (deeper depth of field). A way that I personally remember this is: like body jewelry piercing, the smaller/lower the gauge number, the wider the opening is. Same thing goes with fishing hooks, hypodermic needles, and wire sizes (for amps etc.). So if those examples help you remember that aperture works the same way, then use them! If you have other similar ideas, I would love to hear them!
F/stops are measured on a scale called “the F/stop scale.” F/stops are actually measurements of the diameter of the aperture. If they were expressed as a fraction, this number would tell you the diameter in millimeters as a fraction of the actual focal length of the lens. So for example, if your lens was set at 40mm with an aperture of F/8, the diameter of the actual aperture opening would be 5mm (40 mm/8). Cameras vary on their range of F/stops, some start as low as f/1 and some go up to f/64 (or higher)! When the number isn’t a full number (ex: F/2.8, F/5.6) these numbers can depict half stops, third stops, as well as full F/stops. I will cover stops and ratios further later on.
The standard F/stop scale is as follows:
F/1.4, F/2, F/2.8, F/4, F/5.6, F/8, F/11, F/16, F/22, F/32, F/45, F/64
To demonstrate how changing the aperture can change the depth of field in an image, I conducted the following exercise:
First I set my camera to “Aperture Priority Mode.” This setting lets you manually adjust your aperture and ISO, and the camera sets the shutter speed automatically to the optimum results based on the F/stop of your choosing. Below are three different images which I used the same ISO (400) and the same focal length (38mm), but adjusted the aperture; the shutter speed changed automatically according to the different apertures.
In these images you can clearly see the difference of using a larger versus a smaller aperture. In the first image (F/5), the shell is in focus, but the sand in front of it, the grass surrounding it, and trees and hills in the background are all very out of focus. You can also see that with this image, some of the detail in the shell is lost (especially around the edges). But, your eye is immediately drawn to the shell; there are no other distracting elements because the focus is only on the shell. With the middle image (F/10), you can see that a little more of the detail is brought in with the sand, grass, and even the trees in the background. Middle range F/stops are often times ideal because you retain all the detail of the subject without having too much outside distraction or diffraction in your image. In the third image (F/32), you can see that the sand is much more in focus, the grass is more defined, and you can actually see the detail of the trees in the background (and tell that they are trees!). However, this amount of detail can be considered “distracting” by some, and will not create much of the dreamy bokeh and blur you see in a lot of portraits.
Depending on your overall goal – if you want the subject to be the primary point of focus or if you want the viewer to also notice the surroundings – you can see that changing the Aperture (or “F/stop”) can make a huge difference in changing the depth of field and overall effect of your image.
Dissecting photography terms step by step is one of the most useful things I’ve ever learned to do while learning photography. I really hope you can benefit from our mini-dissection today. Feel free to share this article with your fellow photography “surgeons!”