Whoa!  What?  What the heck is Aperture!?  Stay with me for this lesson ’cause it’s good and it’s important and all kinds of light bulbs will go off in your head when you get this.  😉

When we talk about aperture–listen to this–we will be referring to your LENS, not your camera.  Did you see that?  Read that statement again, I’ll wait for ya.

Got it?


Yes, it’s important to have a ‘good’ SLR camera, but it’s the LENS lets you work magic.

Aperture describes the size of the opening in your lens that allows light in or keeps light out.  Get it?

A larger opening will let more light in and a small opening does what?  The opposite..keeps light out.

Take your lens off your camera and let’s look at it.

If you look at the back of you lens like this, you’ll see the opening I’m referring to.

Next, look at your lens itself.  Your lens length and aperture are written along the edge like this.

The aperture is the F-stop number that’s written such as 1.4, 2.8, 4.5, 5.6, etc.

The lower the number the larger the opening.  The larger the number, the smaller the opening. Yes, it’s opposite, but I don’t know why.

So now.  You tell me why do you think having a lens with a lower aperture is important?

Think about it.

Why?  To let more light to your frame in a low light situation!

Yay!  You got it!

This is a freebie:  you may also hear aperture referred to as the speed of your lens.  A lower aperture is considered a fast lens.  Just a little FYI in case you hear that later and won’t get confused.

This is why in some low light situations and have your ISO turned all the up, but still can’t get a good exposed picture…is because your lens may simply not be capable of doing it.  Why?  Again, most lenses that come with your camera in your camera kit are slow lenses with apertures that start at 4.5-5.6.  These apertures just won’t get the job done for you in low light situations.

Another thing with lower apertures you’re going to get that nice blurred out background otherwise known as a shallow depth of field.  You’ll hear that again, so take note.

This is important.  The lower the number..or smaller the number..the smaller the area of focus.  The higher the number..or larger the number..the larger the area of focus.

So, if you’re taking one person’s picture and even if you’re outdoors, set you aperture to a lower number to get that shallow depth of field or out of focus and fuzzy background that so many of us like.  But if you’re taking a larger group then set your aperture to a larger number so you can get everything in focus.  The aperture you choose is dependent on how much light you require to hit your frame or the depth of field you need (or what you want in or out of focus).

How do you do this?  Simple.  Get your camera off of the fully auto mode and turn your dial to Av or Aperture Value or Aperture Priority.  With this setting, you determine where you want your aperture to be (depending on your situation) and your camera will appropriately set your other settings for you.  Way cool, huh?

Here are a few examples.  These are images I’ve posted before, but let’s review them.

ISO: 1000; Aperture: 1.8

It’s a dark room and I’m not using flash so I need to really open up my aperture to let as much light in as I can so I chose a lower number so more light could reach my frame.  Now, keep in mind that with that lower aperture, my subject is going to be the only thing in focus.  Re-read the above to see why.

ISO: 100; Aperture: 6.7

It’s sunny out so I need to control how much light hits my frame (I don’t need a ton or it would really over-expose my image, as well as, I need everybody in focus so I chose a larger aperture number).

Shooting in Av mode is a great way to learn how to use your camera and learn exposure.  Take your camera outside and set your ISO to 100 and your Av to the lowest it will go.  Choose a still object and increase your aperture with each shot and see what happens. Notice I’m not talking about what your Shutter Speed is doing right now because I just want you to look at your aperture right now.  We’ll talk about Shutter Speed next week.

Here are a few more examples.  Look at each image and think about if the aperture is set lower or higher?

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