Using Your Aperture
As I mentioned in my last article, there are a few different settings on your camera that you can adjust manually in order to create your image. When you learn how to master these, you can start taking photos with your DSLR that set your work apart from your compact camera images. You can begin to unlock the full potential of your camera simply by knowing what your aperture is, and how to adjust it.
Understanding How Your Aperture Works
The first manual setting that I’m going to teach you how to use is your aperture. This can be a complicated subject to learn and can take some time to grasp fully. The more you practice your manual settings in the field, the easier it will get – but for now, you’ll need an overview of aperture before you can head out to practice. Every photo shoot will become a bit easier, you’ll pick up a new trick, and soon, adjusting your aperture and other manual settings will become like second nature.
You’ve probably noticed that some photos will have a nice background blur with your subject in perfect focus, creating an isolation effect to your main focal point, like in the images below:
In this shot of a sandpiper, my subject is in perfect focus while the waves in the background are blurred – this effect was created by adjusting my aperture.
By adjusting my aperture, I was able to isolate the leaves and let the remainder of my image be thrown into a shallow depth of field. If everything was in perfect focus, these otherwise unnoticeable leaves would have been lost in the composition.
Other photos will be sharp and full of detail from the foreground to objects far in the distant background, as seen below:
Alternatively, my lighthouse photo here is sharp from the grass in the foreground to the clouds in the far background.
The amount of your image that is in perfect focus (or, alternatively, lack of) is known as your depth of field – in other words, how much of your photo is in focus and how deep into it can you see clearly? If it’s deep, you can see many elements in sharp detail from foreground to background. If it’s shallow, only a small portion of your photo is in focus while the rest of blurred.
The first images above have a very shallow depth of field (much isolation), while the second image has a very deep depth of field (everything is in perfect focus).
How Do I Control my Aperture?
Your depth of field is not achieved by chance – it can be altered to your liking by adjusting your camera’s aperture. You’ve probably heard of this term or read about it briefly in your camera’s manual. Your aperture has limitations as to how wide it can be adjusted (a.k.a. how shallow your depth of field can get) and also how small (a.k.a. how deep your depth of field can get).
In order to control these limitations manually, you adjust what is called your f/stop number. This number basically gives your aperture a tangible setting to adjust, and is displayed on your camera without the backslash – for example, “f1.8″.
Contrary to what you may think, your aperture is NOT limited by your camera, but rather by your lens. It’s an element inside of your lens that opens and closes as you adjust the f/stop number on your camera. You can click here for a diagram of a camera aperture so you can get a visual of what I’m talking about.
The wider your aperture gets, the lower the f/stop number will be – and thus, your depth of field will become more shallow (more blurry). In contrast, the higher your f/stop number is, the smaller your aperture gets – which means that your image will have a deeper depth of field with more elements coming into focus as you increase your f/stop.
The aperture is located in your lens since light needs to travel through it before it hits your digital sensor. If you look on your lens, you’ll notice that somewhere it will say the minimum aperture setting (like 2.8 or 5.6). This is because each lens will have a different minimum aperture setting which determines who wide your aperture can go. For example, lenses that are often uses for portraits will have a very wide aperture since portraits favor the isolation effect a shallow depth of field can achieve. Lenses with wider apertures are typically priced higher than those with an aperture of say f/5.6 since you have more versatility in what kind of image you can create.
So to briefly recap:
A wide aperture (or your lowest f/stop setting) will give you a shallow depth of field, while a small aperture (or your highest f/stop setting) will give you a very deep depth of field.
Your aperture is a part of your lens that is controlled by your camera, and not a part of the camera itself.
You can adjust your aperture by changing your f/stop, and the range of your f/stop is determined by your specific lens as each lens will have a different range.
Using Aperture to Control Light
Now that you understand the basic functions of your aperture, there is another very important change that happens when you adjust your aperture that affects the exposure of your photo.
As mentioned in the previous article, your camera creates a photo by letting in light. The amount of light that is let in to be exposed onto your sensor is dictated by your shutter speed, which is controlled by your camera.
When you change your aperture, you’re literally widening or shrinking the actual size of it in order to control your depth of field. So for a second, think of your aperture as being a window (which it is in a sense) that you can open and close by adjusting your f/stop. When you have a small window (high f/stop), not much light is being let in, which means that it will take longer to expose the image onto your sensor. Alternatively, if you have that window wide open (low f/stop), plenty of light is coming through your camera, which will cut your exposure time drastically.
If you remember in the previous article, your shutter speed controls how long your image is displayed onto your sensor in order to get the right exposure – each image will require a different speed depending on your light. You can think of your shutter as being another window behind your aperture that will open and close for a certain amount of time.
With this in mind, your aperture will affect how long your shutter speed is because when you adjust it, you’re also changing how much light is being let into your camera (wide open window vs. almost closed window).
There is, however, a way for your camera to let you adjust your aperture manually while still choosing your shutter speed automatically – which will make things much less complicated for you. This setting, called aperture priority mode, is only available on SLR cameras. What it does is that it allows you to adjust the aperture to any setting you desire while letting your camera change your shutter speed to coincide with your new aperture setting. This is an ideal feature as you can now directly control your depth of field without having to calculate an new shutter speed to coincide with it. So now you can focus more on your photography since you don’t have to worry about changing your shutter speed along with your aperture.
Your camera manual will explain how to switch into this mode, but typically it will be labeled “Av” on your dial or something similar.
So, to summarize this last section here:
Your aperture acts as an adjustable window that allows you to not only control your depth of field, but also adjust how much light it let into your camera.
With that in mind, you have to adjust your shutter speed when you change your aperture in order to expose your image properly. If your aperture changes without also changing your shutter speed, your image will either be over or under exposed.
In the next article, I discuss how to control your shutter speed. So far I’ve gone over how your shutter speed controls your exposure, but your shutter can do so much more than that. This is also an article you’ll want to read if you have problems with blurry photos.