Understanding your camera (part II)

Okay it's a beautiful afternoon, but rather than spending it outside, shooting pictures, I  wanted to sit down a write the next part of the post on exposure, this one focusing on the second part of the triangle... aperture.  Why aren't I outside you ask?  Because this stuff is important!!  I mean really important.  Okay, it's not that important, but it is really interesting and it will definitely make you a better photographer if you understand it.  So, let's get (Yay, the Giants just scored) to it.

If you read last weeks post, you know that the exposure triangle is made up of three factors.  Shutter speed, ISO and aperture.  Last week we focused on shutter speed and of course now you have a good understanding of how your shutter speed can affect your photo.  Today we're going to talk about aperture.  So let's start with what it is.  You want the hard to understand version or the easy?  I'm going to assume you want the easy, cause I'm not that smart and that's the only way I know how to explain it.  Put most simply, Aperture is 'the size of the opening in the lens when a picture is taken.'  Now that wasn't so hard to understand, was it?  When you press the shutter release on the top of your camera, a hole opens up that allows your cameras image sensor to catch a glimpse of the scene you're trying to capture.  The aperture that you select tells the camera how much to open that hole.  The larger the hole, the more light gets into the camera -- the smaller the hole, well, you get it, right... the less light gets in there.

Now we get to the part that will really make you sound like you know what you're talking about.  You know how camera people are always talking about f-stops and you've never really understood what they were.  Well, aperture is measured in ‘f-stops’. You'll usually see them written like f/2.8, f/4, etc.  Moving from one f-stop to the next doubles or halves (depending on the direction you've moved) the size of the amount of opening in your lens and the amount of light getting through. 

So far it's pretty easy, right?  Well here's the hard part. Large apertures (where lots of light gets through) are given smaller f-stop numbers and smaller apertures (where less light gets through) have larger f-stop numbers. So f/2.8 is in fact a much larger aperture than f/22. Crazy, right?  Seems like it should be the opposite, but as hard as I've tried, I can't get them to switch it, so that's the way it is.  

Now, why do we care so much about the aperture.  What affect does it have on our photos?  We know, based on last week's post that the shutter speed allows us to affect the motion in our photos. Well, there are a number of results from changing the aperture, but the most noticeable one will be the depth of field that your shot will have.

Depth of Field is that amount of your shot that will be in focus. Large depth of field means that most of your image will be in focus and small (or shallow) depth of field means that only part of the image will be in focus and the rest will be fuzzy.  So when you see a portrait of a person and they're totally in focus, but the background is a creamy blur, that's a shallow depth of field and it's controlled by the aperture.

So that's aperture.  Next time we'll focus on the third part of the triangle that affects our exposure and that's the ISO.  Remember all these tree elements are connected, so if you change your shutter speed and slow it down to allow more light in and give some nice motion blur, you're going to have to change your aperture to a smaller opening (higher f-stop number), to let it less light to have the same "perfect" exposure you had before you changed your shutter speed.  

Shutter Speed + ISO + Aperture = Your Exposure