Exposure Made Easy PART 1: Aperture

by melissa

Understanding exposure is the beginning of understanding your camera, which comes in pretty handy in getting the shots you want. First of all, let's establish something.

Auto does a pretty good job. 

Auto means you're letting your camera guess the exposure you want for each shot. And for the most part, it's a pretty remarkable feature. Your camera is really smart. And if it's easier for you, and more fun for you to stress less about settings, then roll with it!

If you find yourself getting stuck though, or you're constantly wondering "how do I get my pictures to look like that?" when looking at other photography, then there's something you should know: you are smarter than your camera.

Pretty awesome, right? That means if you understand what is affecting your exposure, you can decide exactly how you want to expose every shot. It was a big day for us when we discovered that. It was so nice to be able to CONTROL our own exposure and actually get our shots to turn out the way we wanted them to. Hopefully I can give some tips that will make your discovery a lot quicker than our teach-ourselves, hit-and-miss, read-lots-of-books-we-didn’t-understand-yet, and search-every-online-forum-and-tutorial method. :)

So let's get to it.

Exposure is light recorded into your camera. Easy enough. There are three key exposure settings that determine how light is recorded into your camera, so this Exposure Series will be done in three parts: aperture, shutter speed, and ISO. These make up "The Exposure Triangle." I know it sounds like a lot of big words and there will be lots of numbers thrown around...but stay with me! Getting this will be huge! Each setting in your Exposure Triangle equally affects your exposure, or how light/dark your photo will be.

Today we're tackling aperture.
(see part 2 on shutter speed here)
What is aperture?
Aperture is the size of the opening in the lens when a picture is taken. It opens to let in more light and closes to let in less light. It's like a big eyeball that squints when it's too bright and dilates when it's dark, or at least it should when exposing correctly :) The larger the hole or aperture (also called an f-stop), the more light will hit your sensor. The smaller the hole or aperture (f-stop) the less light will hit your sensor.

Here's a curveball for you, though. It would make sense that a larger number should mean a larger opening, but no such luck. The f-numbers are fractions, so actually, the larger the f-number, the smaller your aperture becomes. The lower the f-number, the bigger your aperture becomes and the more light comes in through the lens. How's that for inconvenient? Check out the chart below to see how much the opening of the lens changes with each f-stop. It's crazy!! I would never have thought it would be that big of a difference. (The bolded f-numbers are those that are most common. If your camera won't let you go down as low as f/1.4, f/2, f/2.8, your camera's not messed up, it's just as low as your lens will go. You can read up on my lens post for more info.)

Aperture also controls depth of field and affects the lighting of your exposure. Depth of what?! No worries, that's where we're headed next. You can't talk aperture without talking depth of field, folks.

What is depth of field?
Depth of field is the amount of your subject that is in focus. An image with a very small depth of field (created with large, *and usually more expensive* apertures) have a lot of dreamy, melted foreground/background with only one segment of the image in focus—see image on the left—while an image with a very large depth of field (created with small apertures) would have everything in focus—see image on the right. The blur (not to be confused with motion blur) created when things are out of focus because of a large aperture/small depth of field is also known as bokeh.

Self-indulging tangent...I may daydream about bokeh, and you may remember my confession here of loving large apertures to a fault for that very reason. It's a style choice and completely a personal opinion, but I like to think of it more as better story telling—allowing the part to be seen that you want to be seen, and forgetting the rest that dilutes the story. Plus...it's beautiful. Just sayin.' :) My lens post has more info on lenses and tips on which can help you get the smallest depth of field and best bokeh. 

Mmmmm, yummy bokeh.

In English, please...
Here is a series of photos taken from the same spot with different apertures. You can see as the aperture gets smaller (and f-stop # gets larger), more of the background comes into focus.

What you CAN'T see, is that with each decreased aperture size, I had to compensate the loss of light by boosting my other exposure settings (shutter speed in this case...that post comes next).

Making your aperture smaller and bringing more into focus will ALWAYS mean a darker photo...UNLESS you compensate for it somehow. See the last image? The black one? Yep. That was to show you, in all its glory, what happened when I went from f/1.4 to f/8 without adjusting my shutter speed or ISO. If you're shooting on Aperture Priority (Av for Canon, A for Nikon), your camera should be making those adjustments for you. In manual mode, it's up to you. But we'll cover that in parts 2 and 3 of the series, so don't panic. Baby steps. Let's rock photography one mind-blowing technique at a time.

Remember these 3 things.

1. Aperture is the opening of your lens.
2. The smaller the number the larger the opening.
3. Larger openings let in more light and have a smaller area of focus (more blur/bokeh/awesomeness).

Photo challenge of the week!
Switch to your aperture priority setting and stay there this week (Av for Canon, A for Nikon). Mess around with aperture sizes and see how it affects your shots. Get the hang of f-stops and a feel for how much will be in focus for each one (try comparing your shots with f/2.8, f/4, f/5.6, f/8, f/11).

Good luck! And let me know if you have any questions!