Seeing in Depth of Field: A Simple Understanding of Aperture

Seeing in Depth of Field: A Simple Understanding of Aperture

Photography can be simply defined as: painting with light.

When you are painting with light, you are creating a story in a split second. That’s what photography is all about. Technically, your camera is measuring the light in the scene, and you are telling it how much of that light you want to use to create a properly exposed image. This becomes your story.

There are three main settings used to control that light; Shutter Speed, ISO and my favorite, Aperture. Each of these settings has its own individual way of measuring light. When all three are balanced correctly, you create a proper exposure.

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Though each of these three settings measures light, they also have unique characteristics that create artistic qualities in your photographs. By understanding them, you have control over the full story you want to tell.

Shutter speed captures movement or freezes it. ISO helps control how sensitive your camera is to the available light in a scene. Finally, the aperture creates depth of field. This is where the real story comes from; it is with aperture that you control what is in focus, and what is out of focus.

As a photographer, how do you decide what you want your viewer to focus on? How do you create a story? That’s what aperture is all about, and that’s why I love it.

WHERE IS IT AND WHAT DOES IT DO?

Aperture is located in your lens, not in the camera body. The lens opening expands and contracts to control light. By selecting a specific aperture size, you are telling the lens how much light you want to hit, and register on, the sensor.

It is very similar to how the human eye works. Your pupils expand and contract based on the available light in the scene. Like when you first walk into a dark movie theater. At first you can’t see, then your eyes adjust. Your pupils expand, allowing your eyes to see as much light as possible in the dark room.

Again, when you go outside on a sunny day, at first it’s too bright to see. Your pupils adjust by contracting, letting in less light. Your lens aperture works the same way. Changing aperture settings is like your pupils dilating or contracting.

The size of a lens aperture is measured in what we call f-stops (fractional stops). Just like all settings on a camera, there is a general range.

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The numbers aren’t necessarily important to memorize. What’s important is to see the range in the settings. Here is the trick; the smaller the f-stop number (like f/1.8), the larger the aperture opening. This means more light will enter through your lens at once, and vice versa. The larger the f-stop number (e.g. f/22), the smaller the aperture opening, and less light will enter your lens.

Think of these f-stops as fractions. Just replace the F with the number one. 1/4 of a pie is much more than 1/16 of a pie.

A quick note: Not all lenses are built the same. Different lenses have different apertures. Some lenses have a wider range and some have less. Standard lens will range from F3.5–F22. Specialty lenses go as low as F1.2 or more. See: What the Numbers on your Lens Mean for more on this.

SEEING IN DEPTH OF FIELD

Here is where it gets fun. While measuring light, when the lens expands and contracts, it also measures depth of field. Again, your eyes do the same thing!

As you look at the screen to read this, these words are mostly in focus to your eyes. In your peripherals, you can see other things, but they aren’t in focus.

Notice, your hands on the keyboard, they are in the foreground, and perhaps a bookshelf is in background. You can see them but they are not in focus. You are seeing in depth of field.

A great photograph does just that. It captures a foreground, a mid-ground and background. By setting your aperture you are controlling which of these areas is in focus. It is all based on your intention, your story.

DEFINING DEPTH OF FIELD

With your camera’s focal point (that little square in the middle of your viewfinder), you focus on a particular part of the scene. This point becomes the sharpest part of your image. There is an area in front of that point in focus, and an area behind it in focus as well. The distance from front to back that is acceptable focus is considered your depth of field. You decide what is acceptable by choosing a specific aperture size.

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This is a story about a monkey on a cliff. The bushes in the foreground and the temple on the cliff in the background are out of focus. They are out of the depth of field. This brings your attention to the focal point; the monkey in the middle (no pun intended).

Remember, the lower the f-stop number, the bigger the opening, the more light comes through the lens. This means less of your scene is in focus and you have a shallow depth of field. The opposite is also true. The larger the f-stop number, the smaller the opening, the less light comes through the lens. In this case, more of your scene is in focus and you have a greater depth of field.

Simply put, the larger the f-stop number, the more will be in focus. The smaller the f-stop number, the less well be in focus.

A DEEPER LOOK AT DEPTH OF FIELD

As you lock your camera’s focal point on a specific spot, that spot creates a focal plane. Everything that is the same distance away from the lens is on the same focal plane, and will be in focus.

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At a shallow depth of field (low number), the focal plane is very thin. As your depth of field becomes greater (high number), the focal plane becomes deeper.

Here is the same scene photographed with different aperture settings. Notice that the depth of field changes how much of the image is in focus.

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At f/2.2 only the sunglasses are in focus. At f/5.6 the hat is also in focus. By using f/8.0 you can start to make out the trees in the background. Finally, at f/22 everything in the image is in focus.

Which one tells the best story? You as the photographer, get to decide.

PRACTICE TIPS AND TRICKS

Now that you’ve got a good grasp on the basics, it’s time to play! Here are some great tips to start your practice.

Set your camera to Aperture Priority mode. You will have full control of the aperture, without having to worry about proper exposure. This way you can just focus on depth of field. It’s a great way to fully understand what your lens is doing as you change your aperture settings.

Pick a subject or scene, and stick with it. Photograph your scene from many different angles. Choose different parts of the scene to focus on using the full range of aperture settings.

Use these guidelines to capturing depth of field in different scenarios:

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When shooting single subjects, like a portrait of a child, it is best to use a lower f-stop like f/1.2-f/2.8. Creating a shallower depth of field brings attention to the subject’s face, which is always most important in a portrait.

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When shooting a small group of people (2-5), choose an aperture of f/4-f/8. This, being a slightly deeper depth of field, guarantees that everyone in the group will be in focus.

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Any time you have a wide-open scene, for instance a landscape, and you want all of that landscape in focus, choose a setting above f/10.

These are just guidelines. Photography is a form of art. Be creative, and remember, it’s all about telling a story.

What story do you want to tell? Share your images here and show how you’ve used depth of field to create a great story.

All Images in this article are © 2015 Danielle Werner and DEW Imagery & Design

 

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Danielle Werner is a free-spirited photographer, designer and retoucher, on an endless journey around the world. She is also a passionate writer and educator who teaches photography workshops wherever she goes. Read Danielle's inspirational travel stories at LiveWonderful.com, and check out more of her adventure and lifestyle photography at DEW Imagery & Design.