When you first get a DSLR, one of the first things you might be trying to figure out is how to get a blurry background in your pics. You see the pros always turning out these pics where the eyes are tac sharp, but everything behind the subject is “blurry”… smooth as butta.
This background blur helps the subject stand out. It also means that you don’t have to worry about the background. In time, you might just choose a background because of the color, knowing that it’ll be blurred out but still translate the color.
So here’s the 3 ways to get that background blur.
This is the one that most people are familiar with. Aperture is simply the term for how big or small your lens opening is. Aperture is to a lens what the iris is to your eye. It adjusts in size to let more or less light in.
We call different aperture sizes f-stops. f-stops were created on opposite day. The lower the f-stop, the bigger the aperture. The higher the f-stop, the smaller the aperture. So f2 is a big lens opening. f22 is a small lens opening.
Translate it just the one step further: f2 is a big aperture. f22 is a small aperture.
If you’ve taken our FREE mini course about understanding exposure, you’ll get to see my 4 year old explain this. She’ll tie it into how it affects exposure as well as depth of field. And with a homemade camera made out of a bandaid box. 🙂
Big openings (apertures) produce a shallow depth of field (DOF). Small apertures produce more DOF. Depth of field (DOF), btw, simply means how much space is in focus behind your focal point. And in front of it.
Say you’re taking a pic of your kid. You set your aperture to f2. You focus on the eye…and click. The pic might very well have the eye in focus, and yet the ear is slightly out of focus, merely inches behind the eye. That’s a small DOF.
On the other hand, you might choose f22. And in this case, a tree 200 ft behind your kid is in focus. This is a large DOF.
So naturally, the primary way to get a blurry background is to choose a large aperture. Your kit lens might only have a maximum aperture of f3.5 or even f5.6. This might be a bit frustrating as it won’t produce the dreamy blur of “faster” lenses like this 50mm 1.4. And by fast, we don’t mean that it focuses fast. We mean that it let’s in such a HUGE amount of light at f1.4 that we can have a fast shutter speed. Again, if that’s a little fuzzy, this free mini course is for you.
I have a lens that goes to f2.8. I’ll be using it for this lesson because it also zooms. And that’ll help me illustrate the next two points. Anywho, check out the difference in DOF between f2.8 and f16:
Here’s the first pic at f2.8 (notice the background blur):
Here’s the same spot but now at f16 (notice there’s much less background blur):
2. Focal length
Now that we have #1 out of the way, the next two will come a bit easier.
Focal length is basically just a term for how far your lens reaches. So a 24mm lens is a wide angle lens. It has a wide field of view. A 200mm lens is a telephoto lens. It reaches out far and has a narrow angle of view.
With the aperture remaining equal, the more telephoto your lens, the less DOF you’ll get, and thus the more background blur.
Translation. Set your 24mm lens at f4. Set your 200mm lens at f4. Take the same pic from the same spot. Your 200mm lens will give you less depth of field.
Here’s my example with my 70-200 lens. This just means I can zoom from a 70mm focal length to a 200mm focal length. I’ll leave the aperture “wide open” (as big as it gets) at f2.8. I take each pic from the exact same spot. All I’ll do is zoom from 70mm to 200mm
Here’s the pic at 70mm (we can easily make out the backgrounds).
Here’s the pic at 200mm. Obviously it’s a tighter composition. But notice how the back door is less in focus (less DOF). Actually, notice that Payson is not even in focus. He’s mere inches behind Kerbi’s eye (the focal plane). This is a very shallow DOF!
3. Distance to subject
Last one. With aperture being equal AND focal length being equal, you’ll get less DOF the closer you are to your subject. You’ll get more DOF the further away you are from your subject.
Said another way: When I take a pic of my kid at 200mm f2.8 from 5 feet away, I’ll have much less DOF than when I take the the pic with the same settings but from 50 feet away.
Let me show ya.
My lens is set to 200mm and f2.8. Here’s a pic from 5 ft away. Notice how the background is completely out of focus. Just smooth creamy colors. There could be a green monster back there as the background and we wouldn’t know it. Even here ears are out of focus. There’s only a couple inches of DOF here.
Now I move back to yard…about 30ft away. I still focus on Kerbi. I’m still at 200mm. I’m still at f2.8. Everything is the same. But since I’m further away (distance to subject), I have more depth of field.
So, here’s how to get the most background blur out of your crappy kit lens.
Kit lenses are often 18-55mm f3.5-5.6. This means it zooms from 18mm to 55mm. At 18mm the max aperture is f3.5. At 55mm the max aperture is f5.6.
So do we choose f3.5 at 18mm, or f5.6 at 55mm? Well, that’d be a good experiment for you to try. 🙂
Spoiler: Reach as far as you can as wide as you can. And then get as close as you can. Then you’ll have the most background blur possible.
Speaking of more zoom…today’s the last day to enter to win (FREE!) an olloclip telephoto: