Understanding Aperture: the Key to Being Artistic

f/5.6 Aperture Example / Photo by Rachael Olson

People often ask me how to get a blurry background. Something about a blurry background makes people think “professional”.
First, if you want to sound cool, call it bokeh (pronounced: boke-uh), which means “haze” or “blur” in Japanese.
Next, you need to understand depth of field. This way, you don’t let in just enough light, but instead you control depth of field to achieve what you want artistically.
The depth of field is the area of sharpness within a photograph. Although focal length and distance between camera and subject affect it, the simplest and most effective way to change your depth-of-field is to change your aperture.
Your aperture is basically just a hole letting light in. Think of it this way: the shutter (controlled by shutter speed) opens and closes over the hole. The wider the hole, the more light coming in to the sensor in the amount of time the shutter is open.
“F-stop” refers to aperture. The higher the f-stop the more narrow your aperture (hole letting in light). Your lowest f-stop is referred to as “shooting wide open” because the lower the f-stop, the wider the aperture. The lowest and highest f-stop you can choose depends on your lens. If you hear someone refer to a “fast lens” they’re talking about a lens that can open up wide like to a f-stop 2.8 or 1.8, which is even better (thus, they can use a fast shutter speed and still get enough light). Love fast lenses. But that’s a discussion for another day….

f/2.8 Aperture Example / Photo by Rachael Olson

Lower F-stops (wider apertures) will blur background. Higher F-stops (more narrow apertures) will have more in sharp focus.
If you remember nothing else, remember these words go together:

• Small aperture – lower f-stop – wide – open – more light – less depth-of-field
• Large aperture – higher f-stop – closed – stopped down – narrow – less light – greater depth of field

I think of it like a stack of paper. Imagine that your focus point is on a piece of paper in that stack. That plane will be sharpest and then each piece of paper will get progressively less in focus as you move away from that plane. You’re telling your camera how quickly to move out of sharp focus. Just a note: anything in front of the focus point will go out of focus a lot faster than the points behind the focus point will. So if you’re taking a picture of a large group, focus on the person closest to you.
The best way to get this into your brain is to play with it:

1. Set your camera on Av mode. This will allow you to change your aperture and the camera will automatically choose a shutter speed. Less thinking for you!
2. Choose a subject that holds still – a newborn or an object. Definitely NOT a 2-year-old. Make sure you are in bright light. Place it where you can see a lot of background for comparison of depth of field.
3. Take a picture of the same subject in at each of these apertures:

f/2.8 (if you have a fast lens)      f/5.6                      f/7.1                      f/11
Now, compare your images on your computer screen. You should be able to see a difference, especially between f/5.6 and f/11.
After you’ve done that, the following guidelines should make sense:

• Use lower apertures when you want a blurred background. Remember to think about the paper analogy or you could end up with weird portraits with one eye in focus and the other out-of-focus – if you’re open too wide and the subject’s head is even slightly turned.
• f/11 is often considered a “safe” aperture for portraits if you don’t need to worry about getting a bokeh. This makes sure the entire face stays in focus.
• When you want the background in focus, or when doing landscape shots, use the highest possible aperture to capture all of the detail.
• When I don’t really care about the aperture, because everything is pretty much on the same plane of focus, I choose f/8.

Understanding how to use aperture will allow you to move from merely correctly exposed images to creative images. And then you won’t only sound cool, your pictures will look cool too!

f/10 Aperture Example / Photo by Rachael Olson    http://www.spectrumphotographytips.com/understanding-aperture-the-key-to-being-artistic.html