Photography Facts – The 5 Things You Need-to-Know about Aperture

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What the heck is Aperture?  When you begin learning photography, there are so many terms to learn.  “Aperture” is just one of the many bits of jargon to sift through.  It can be overwhelming, so let’s make it easier with five facts that you need to know about Aperture.  What is it, how do I control it, and how can I use it to improve my photography?

1 - What the Heck is Aperture Anyway?

In short, the term Aperture refers to the opening in the camera lens that allows or blocks light from coming into the camera and reaching the sensor.  Since photography is 100% based on how much light comes into the camera, this is a fundamental principle to understand.

Here is the more scientific, albeit geeky (it’s okay if you’re on the geeky side. Sometimes I am, too), answer, from Wikipedia: Aperture is defined as a hole or an opening through which light travels. You can see the full definition HERE

A moving diagram of how the blades open and close within the lens.

A GIF image of the Iris, diaphragm, and blades inside a camera lens
By Pasimi - Own work, CC BY-SA 4.0,

In the case of photography, there is a diaphragm inside of the camera lens that blocks light. In the center of the diaphragm is an Iris. The Iris is the name given to the blades that open and close to allow light through the diaphragm. If you want to dig deeply into the inner workings of a camera lens, you can see more from Wikipedia HERE

In the meantime, here are a couple of diagrams I’m borrowing from Wikipedia that help visually show what all of that looks like:

You can see below how the lens can open and close through the f-stop settings in the lens.

An image of the aperture openings inside a camera lens
By KoeppiK - Own work, CC BY-SA 4.0,

2 - What Does Aperture Do?

We know that the aperture setting determines how much light is allowed into your camera. That’s what photography is all about – letting light into the camera!  But if it were that simple, there wouldn’t be an exposure triangle.  So, it’s essential to understand what this one piece of the triangle does.  Aperture affects two things in your photos:  depth of field and exposure.  You can read about how aperture affects Depth of Field in Take Your Photos to the Next Level by Understanding Depth of Field.  Here let’s focus on how Aperture affects exposure.

When we talk about exposure, we are referring to how light or dark your photo is.  A lower aperture (big # – we’ll get to that in a minute) doesn’t allow as much light into the camera, thus making your photo appear darker.  A larger aperture (small #) opens that iris up more to allow more light into the camera and onto the sensor, thus making your photo brighter.

A diagram of aperture as related to the camera shutter in manual mode

Of course, we wish to find the perfect balance, which brings us back to the triangle.  The reason we have a triangle and work with more than just aperture is that there are times when we intentionally want to allow less light in, but we still need a correct exposure.  When that happens, we need to find another way in which to let the light.  Shutter Speed does the trick rather nicely.  A great example of this is when creating a Starburst in your photos.  Check out how that all comes together in Epic Photography – Capturing A Perfect Starburst Is Easier than You Think.

I digress.  And now we return to the subject at hand.  Now that you know what aperture does, time to understand how to control it.

3 - What Controls the Aperture?

The lens that you are using on your camera controls the Aperture.  When I began learning, I had some confusion about what parts of the camera controlled the parts of the Exposure Triangle.  If you need a refresher on the Exposure Triangle, be sure and take a look at Your Ultimate Guide to Shooting in Manual Mode.  I eventually learned that the lens entirely controls the aperture.  The other two parts of the triangle are ISO and Shutter Speed.  ISO has to do with the sensor that lives inside of your camera body.  Shutter Speed is also entirely determined by your camera body.

Since your lens solely controls the aperture, you can begin to see why the right lens for the job becomes very important.  Once you understand how aperture works, you can then start to understand what situations call for more light in your camera.  Controlling aperture allows you to let that light in without compensating with a higher ISO, which can result in a grainy photo, or a slower shutter speed, which can result in motion blur.

Of course, it’s lovely to know that the lens controls the aperture, but how do I know what aperture I have on my lens?

3 - What Aperture is my Lens?

There are a couple of ways you can determine the aperture range on a lens.  If you are considering a new lens, you can ask or check the item specs on the listing online.  It seems pretty basic, but what if you already have a lens and you would like to know what the aperture range is?  The first way is to look at the outside of the lens.  As you can see below, the lens will have the specs printed on the exterior.  Looking at this information, we can see that this lens has a 70-200mm focal range, a maximum aperture of F/2.8, and then lists some of the other features.

Showing specifications of specific lens

Another way is by putting the lens on your camera and manually adjusting the aperture to the largest and smallest #’s possible.  If the lens is a zoom lens, then be sure and check these numbers at the closest and the furthest levels of zoom.  It is important to note here that some zoom lenses have a variable aperture setting.  In other words, the widest aperture at the closest distance will differ from the widest aperture at the furthest reach.  For example, as you can see below, this lens is an 18-55 zoom lens.  The numbers 1:3.5-5.6 indicate that the widest aperture at 18mm is 3.5 and will decrease to 5.6 (remember – bigger # = smaller aperture) as the lens zooms to the widest view of 55mm.

Showing specs of a variable aperture lens

If you are going to be shopping for a new lens, then do your research!  It is almost always better to have one with a high aperture (lower #).  When you can let the maximum amount of light as possible into your camera through the lens, you will be able to use a lower ISO (less grainy) and faster shutter speed (less motion blur).  This answer is simple, but it covers the basics.

You will see when you begin shopping that lenses with high apertures (lower #s) have a higher price tag.  Why?  Because faster lenses tend to have higher-quality glass elements and an iris with more blades that are thinner, they create a wider maximum opening — these shifts in design call for more engineering and more expensive materials.  So, as my dad would say, you get what you pay for. 

The only thing left to learn is how to sound like a pro when you’re talking aperture in photography.  Just kidding, there’s always more to learn, but for now, let’s talk about the jargon.

5 - F-Stops and Other Aperture Lingo

Now that you’re feeling knowledgeable about what aperture is and how you can use it, I would be remiss in not warning you of all the terminology that you will begin to pick up on when photographers are talking aperture.  Here’s a handy mini list of terms and what they mean:

  • F-Stop
    As you now know, the aperture is the opening in your lens that allows light into your camera.  F-stops are the measurement term for how far open you have your aperture.  They measure the size of the opening in your lens. It is super important to note here that talking about aperture becomes a bit confusing because the numbers that correspond to different f-stops are listed backward.  For example, an aperture of f/8 is smaller than an aperture of f/2.  The lower the number, the larger the opening.  And vice-versa the larger the number, the smaller the opening.
  • A Fast Lens
    A “fast” lens is one that has a very large aperture.  The bigger the aperture, the more light that can get to the sensor, thus allowing a faster shutter speed, hence a “fast” lens.
  • Wide-open
    When you shoot with your lens “wide open,” you are shooting with your aperture as large as possible (smallest #). Therefore, you are shooting with your iris “wide open.”
  • Stopped down
    A ‘stop’ is a halving (or doubling) of the amount of light being funneled into your camera.  “Stopping down” refers to lowering the aperture by this measure.  If you stop down your aperture, you are reducing the amount of light entering your camera by one stop (or half).  The term “stop down” can also apply to shutter speed and ISO.  When you “stop down” your lens, you are closing your aperture (bigger #).

For more photography terms, be sure and read Ten Need-to-Know Photography Terms for the Beginner.

Mastering Aperture Requires Practice + A FREE Cheat Sheet

Congratulations!  You are almost an expert on Aperture!  Now to seal the deal, you’ll need to get out there and get some hands-on experience in adjusting your aperture!  But first clip out this handy Cheat Sheet as a reference to use when you’re in the field.  

Aperture Cheat Sheet

Remember – you can never have enough practice when you’re learning settings, so it’s time to break that camera out and get shooting!  Have fun and be sure and join me on my Facebook Group HERE to show off your work! 

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