Photography Tips Part II: Aperture and Depth of Field
This is the second in a series of posts I’m doing about photography. I’m approaching this as if I’m speaking to novices with no knowledge beyond pointing and shooting an automatic camera. This post will be focused on (har har) aperture and depth of field. If you don’t know what that means, don’t let it scare you. It’s actually very simple.
Part II: Aperture and Depth of Field
There are two things that control how film is exposed in a camera. One is the shutter, and one is the lens aperture. The shutter is the thing that opens and closes, exposing the film to light. The aperture is an opening that controls how much light is let in when the shutter opens and closes. Here’s a picture of an aperture (this is an old Russian film camera):
The aperture consists of the metal blades you can see inside the glass of the lens. In the photo above, the aperture is narrow. In the pic below, it’s open wider:
So that’s what the aperture is. But what does it do besides control how much light hits the film when the shutter opens?
Depth of Field
The aperture controls something called the depth of field. Depth of field refers to how much of a photo is in focus.
In the photo above, there is only a small strip of sand that is in focus. This is a rather narrow depth of field. In this next photo below, everything is in focus, from the ground in front to the mountains way far away—this is a wide depth of field.
Depth of field is fun to play with. It lets you highlight your subjects in different ways. It’s probably most commonly used to make the background of a photo blurry. Below is a photo of a leaf hanging on a tree, with another leaf and another tree in the background:
If I hadn’t blurred out the background, the leaf would have been in competition with both the other leaf and the tree in the background for the viewer’s attention. But with the background blurred, the leaf stands out and the background shapes almost look like its shadow.
You can do more than blur out the background, though. You can blur out the foreground. Below is a photo of an abandoned gas station, with the fence in front blurred out.
You can also blur both the foreground and the background, as in the photo of sand I posted. Here’s another example, this time with not such a narrow depth of field:
So, how to achieve this blurriness?
It depends on what kind of camera you have. 
Some point and shoots don’t have aperture settings. But many do. If there is a setting on your camera labeled “A,” that stands for aperture. If you use that setting, the camera will place emphasis on your aperture setting (over the shutter speed setting).
Bigger = smaller.
Here’s where it gets a little confusing. The aperture settings are actually fractions. So the bigger the number, the smaller the aperture. Most cameras have aperture settings ranging from about 2 to 16. So setting your aperture to 16 would mean it is very small. Setting it to 2 would mean it’s open all the way.
Sidenote: Some lenses are better than others. A good lens will remain sharp with the aperture all the way open. A poor lens will get soft or blurry with it all the way open. (Although some people prefer soft lenses, just depends on what you’re going for!)
Now the stuff you care about.
To make the background behind your subject blurry, you want the aperture open as far as you can, which means the lowest number: 2, or 2.8, whatever your camera has as the lowest. And you want some distance between your subject and whatever is in the background. That’s important—the greater the distance between your subject and the background, the greater the blur.
To have the middle of your range in focus and the front and background blurred, use a middle aperture setting. Which is usually 5.6. This is a fun setting to mess around with. Try it out on rows of things. Chairs, people, whatever. Line them up in a row going away from you and try this setting.
To have everything in focus, use the smallest aperture setting, which remember, is the highest number.
Next up: Fun with shutter speeds. Action shots, low light shots, etc. Good stuff!
To read Part I of this series, “Composition,” click here.
Posted on May 28, 2008, in Photography. Bookmark the permalink. 26 Comments.
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Please please please don’t stop doing these photography posts. I love it when people help out the newbs!
The pictures of the camera are EXCELLENT. And this is a fine, fine article, Susan — Thanks!
Susan, I’ve always wondered what to do with all those numbers- you’re inspiring me to dig out my two SLR cameras!
What kind of SLRs do you have, Tracy?
I should’ve invited people to post links to pics they’ve taken that demonstrate depth of field. Feel free to do so if you have any.
Susan, after you first post, I went out and bought a SLR camera – the Nikon D80. I have no idea what I’m doing. I’m with kwk – keep these posts coming. This is a good way to learn and I love the example photos.
Awesome as usual.
Will you also cover the relationship between aperture and shutter speed as well in the next post?
A little bit. Cameras these days handle all that stuff for you automatically. (I actually do a lot of shooting with my Russian SLR, the one pictured above, and the light meter in it doesn’t work, so I just use the sunny 16 rule.)
I have an older metal-body Cannon, and I have a newer Nikon- but exactly one year and one day after I bought it, the auto-focus broke, and it costs more to send it to Nikon and have it fixed than to buy another one.
I just need to learn how to use them the old-fashioned way.
Susan, what’s the sunny 16 rule?
The sunny 16 rule is a way to estimate what aperture/shutter speed combination you need to get a good exposure if you don’t have a light meter (which won’t apply to your camera at all).
This is how it works. Whatever film speed you’re using (on your camera, it’s the ISO setting), you set your shutter to the same (or closest) number.
If you’re using 100 ISO, you’d set your shutter to 125. If you’re using 200 ISO, you’d set your shutter to 250. Whatever number is closest to the ISO setting.
If you’re shooting in sunny conditions, you set your aperture to 16. And that should give you the right exposure.
You can adjust from there. If you want to use a bigger aperture, you use a faster shutter speed. Or if it isn’t sunny, or you’re in shade, you go with a bigger aperture. There’s a lot of guesswork involved, but once you get the hang of it, it gets pretty easy. Again, not something you’ll need to worry about with your DSLR.
This is what aRJ was asking if I’d cover in my next post, basically.
I’ll wait to see your photo examples in your next post.
These posts are really helpful. I’ve got a Canon Powershot point-and-shoot, but it has manual settings as well. I’ve been meaning to learn how to use them rather than simply rely on the auto setting. Explaining this stuff in simple terms is very helpful.
I think a lot of people are in your situation, Greg. You can get a good digital camera that has manual settings (although not SLRs, they just mimic them) so cheaply nowadays. And DSLRs have really come down in price too.
Even if shutter speed is automatic it is still helpful to understand that it is going to vary as you change your aperture. This can come into play if you are shooting a scene with movement or it you have shaky hands. If you have a very narrow aperture the camera is going to compensate by having a slow shutter speed and longer exposure. Depending on conditions this might make moving objects blurry or demonstrate how unsteady your grip is. A large aperture will let more light in and therefore require less exposure time and will tend to have the in-focus portion of the image be sharper if there is movement.
What John said.
I love, love, love playing with depth of field. It can totally transform a picture. It’s a great way to draw attention to your subject and get rid of other distractions.
I love Susan’s examples, here are some of my shots using short depth of field that I really like.
Abby, you have a great camera, when I bought my DSLR it came down to the D80 and the 400D that I ended up buying. The best thing you can do is take it out and just start playing with the settings. Change the speed and take shots to see how it affects your picture, then change th aperture to do the same.
Great posts Susan, I’ve always enjoyed your pictures, and I think this is very informative.
jjohnsen, I have been playing with all the settings. Unfortunately I have played with too many of the buttons and don’t know how to get it back to the original settings. So, my pictures are turning out rather crappy. I guess a great camera is only as good as the person pushing the button!
Those are great, JJ. I especially like the last one that’s way off center.
Abby if you can’t figure it out feel free to drop me an email (whenigodeaf at gmail dot com) and I can try to help you.
Abby, in your menu there’s usually a choice to return to factory settings, you may want to start with that. Also, while Susan’s posts are helpful, you may want to try some hands-on help. My local camera store offers very cheap basic digital photography classes. Mine went over the basic settings for the camera and it was only about $10.
Susan, I’ll be emailing you shortly.
jjohnsen, I found the menu and believe I have reset the original settings. I’ve already called the store where I bought the camera and they offer a series of classes I can attend – for free, which is a bonus. Thanks for your help.
I’m still trying to figure out how to get my Canon Powershot to cooperate, but here’s a photo I took yesterday using Susan’s advice.
That’s neat, Greg. Makes me want a popsicle!
Email me and maybe I can help you figure out your camera.
Please Help!! I have a Fujifilm S5000. I’ve been using the aperture #’s to try to get the blurry background and it’s just not happening. If I do it on Manual mode I can set my aperture and shutter speed. What range should my shutter speed be? If anyone has this camera could you give me step by step directions. Thanks.
Misty, my camera is an older version of yours.
First, put your camera in Aperture mode and set the aperture to the lowest number there is. (Probably 2 or 2.8)
Switch to Manual mode. You should see a line with a minus sign and plus sign on each end with an indicator pointing somewhere along the line. The up and down arrows on the ring around the menu/ok button adjusts the shutter speed. Go up or down until the indicator is in the middle of the plus/minus line. This adjusts the shutter speed to the correct exposure. (If the indicator is towards the plus sign, there’s too much light. If it’s near the minus sign, there’s not enough.)
Remember that you generally need some distance between the foreground object in focus and the background area you want blurred.
If my instructions aren’t clear enough drop me an email. whenigodeaf@gmail.com
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