Aperture–The Big Three of Photography Part 1

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This is part of a series of posts about How to Shoot in Manual Mode. Follow the links to read the other posts about WHY I USE MANUAL MODE, SHUTTER SPEED, ISO,

HOW I PUT THEM ALL TOGETHER, and WHERE TO BEGIN CHOOSING YOUR SETTINGS! You can also download a helpful Manual Mode Cheat Sheet here.


Light is what makes a photograph. If there is no light, there can be no photograph. It sounds harsh, but it is true.

Aperture, shutter speed, and ISO are the 3 things that control how much light is recorded by your camera. You need to understand each one and how they work together to get a good exposure while using Manual mode on your camera.

My Photo Friday posts for the next few weeks will cover what each of these things are and how they each help to make a photograph.

I hope these posts will help you understand, in a very simple way, what these somewhat intimidating words mean. EVERY camera has each of these things–however, with most point-and-shoot type cameras, you don’t have full control over how they operate.

We are going to start with my favorite of the Big Three–aperture. Aperture is like the pupil part of your eye. It can be opened up or closed down depending on how much light you want to enter your camera.

When you are in a low light situation you want the aperture opened up as much as possible to let in lots of light in much the same way that the pupil of your eye opens up and becomes larger when you are in a dark room. In bright situations you might want the aperture closed down to allow in less light much the same way your pupil becomes very small when outside on a bright sunny day.

The camera lens (the big thing that sticks onto the front of your camera and can be removed and changed) is the “eye” of the camera and is where the circular aperture mechanism is found. The camera controls how open or how closed the aperture is in much the same way your brain controls your eye.

The setting on your camera that tells how open or closed the aperture is are called f-stops. The most confusing thing about aperture and f-stops is this: the smaller the number the larger the opening and the larger the number the smaller the opening.

So an aperture of f/1.8 would mean that your aperture was open very wide and an aperture of f/22 would mean that your aperture was very closed down (small.)

This next little bit about aperture is why aperture is the my favorite of “The Big Three.” Aperture controls your depth of field. Depth of field is quite simply the amount of your picture that is in focus.

The more open your aperture the less depth of field you have. Here are some examples of this:

If you look at the photo below, you will notice that only the chalk and the pavement directly to the right and left of the chalk are in focus. Everything else is out of focus. This photo has a very small depth of field. This photo was shot at a very wide open aperture of f/2.2.

This next photo was also shot a fairly wide open aperture of f/5.6. Notice that just the one stalk of grass is in focus and everything else in front and behind that stalk are at varying degrees of focus.

The stalks that are fairly close to the stalk of grass that is in focus are just slightly out of focus–you can still distinguish what they are. However, the grass and road in the background are so out of focus that they are indistinguishable.

Here is an example of a much smaller aperture of f/16. Notice that the landscape as far as the eye can see is in focus.

So to sum up–a wide open aperture lets in lots of light but only allows a small portion of the photograph to be in focus. Wide apertures are the smallest numbers or f-stops (ex. f/1.8, f/2.2, f5.6). Closed down apertures let in much less light but allow much more of a photograph to be in focus. Smaller apertures are the largest numbers or f-stops (ex. f/13, f/18, f/22).
I’d love to know if you have more questions about aperture. Feel free to ask them in the comments and I will answer them.

6 Responses to “Aperture–The Big Three of Photography Part 1”

Beth GrahamFebruary 19, 2010 at 10:17 amYou did a great job of explaining this concept! I thought I’d share one other thing that has always stuck with me for understanding how aperture controls depth of field. It goes right along with the eye analogy you used in your post.

Think of someone sitting in the back of a classroom and squinting to see the chalkboard. They are squinting which makes their eye smaller in order to see more things in focus. Just as the smaller aperture opening (larger f-stop) brings more of a picture in focus. Hopefully, this explanation is as clear as everything you already wrote!

Mom and CameraFebruary 19, 2010 at 10:50 amI like the squinting part of the analogy, too.

LaflecheFebruary 20, 2010 at 12:12 amOk. Your explanations are perfect… very understandable. I have a Canon Digital Rebel xt SLR… where would I be able to change the aperture on that?

Mom and CameraFebruary 20, 2010 at 8:01 amSince I am not as familiar with Canon cameras as I am with Nikon cameras, I can’t answer this perfectly. Definitely check your camera owner’s manual. However, most camera’s have a dial that is used to adjust shutter speed and aperture. Make sure the main dial on top of your camera is set to M.

The smaller dial between the shutter release and the main dial is how you will change your shutter speed. I think that in order to change your aperture you have to hold down another button while using that same button. I think it might be a button called “AV.” I am not 100% sure of this–just based off the couple of times I have used my sister’s Rebel. I hope that helps.Lafleche

February 20, 2010 at 7:02 pmThank you so much. I find your blog so inspirational and helpful. You take amazing photos. Really. Thanks for sharing.

Nicole February 24, 2010 at 2:08 pmGreat post Gayle. These terms are tricky and I think you did an excellent job explaining things. I will bookmark this post and come back to it when I need a refresher/clarification. Looking forward to more from you!

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