5 Things Your Camera Won’t Tell You About Aperture Blades and F-Stops

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5 Things Your Camera Won’t Tell You About Aperture Blades and F-Stops

What the heck are aperture blades and f stops, and where are they in my camera anyway?  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, aperture blades are part of the mechanism within the camera lens that allows or blocks light from entering the camera and reaching the sensor.  Since photography is based on how much light comes into the camera, this is a fundamental principle to understand.

Here is the more scientific, albeit geeky, answer (it’s okay if you’re on the geeky side. Sometimes I am, too) from Wikipedia:  “Aperture is defined as a hole or an opening through which light travels.”  You can see the full definition HERE.  Aperture blades open and close that hole allowing or stopping light from reaching the camera sensor.

This moving diagram of how the aperture blades open and close within the lens gives a great vision of what is happening inside the lens when you adjust your aperture.

A GIF image of the Iris, diaphragm, and blades inside a camera lens
By Pasimi – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=69896076

All the fancy words

Let’s get all technical for a minute.  In photography, there is a diaphragm inside of your cameras lens that blocks light. In the center of the diaphragm is an Iris. The Iris is the name given to the aperture 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

Take a look at the diagram from Wikipedia that visually shows 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, https://commons.wikimedia.org/w/index.php?curid=78136658

What is an F-stop?

Spend any time shooting in manual, and you will hear the term f-stop concerning aperture.  The f stands for focal length. The number behind the F is the ratio of the lens’ focal length to the diameter of the entrance pupil.  That’s a whole lot of info to process.  No worries.  You need to know that the number correlates to the size of the opening of your aperture.  It’s just that simple.

Aperture is written as an f/number because it represents a fraction.  Think of your f/stops as the fraction of how far open the diameter is in s iris of the camera.  If you know basic math, remember that the bigger number on the bottom means a smaller measurement.  For example – ¼ cup is smaller than ½ cup.

The same mathematical theory applies when looking at f-stop and why an f/stop of f/22 is smaller than an f/stop of f/2.8.  Starting to make sense?  This information took forever for me to get into the logic portion of my brain!  I could not understand why a bigger number was equal to a smaller aperture for the life of me.  This is why you will see in almost all of my posts that I put the words (bigger number) or (smaller number) behind any mention of wide-open aperture or stopped down aperture.  I need those words for myself, but I also think others out there like me need the reminder.

If you want to use a large aperture, you want a smaller number, like f/1.8 or f/4.  If you’re going to use a small aperture, you want a larger number, like f/16 or f/22.  It makes sense, right?

Fun fact!  Way back in the early days of photography, the photographer manually adjusted the opening on the lens (or f-stop) by inserting metal plates into the front of the lens.  Each plate was called a “stop” because it stopped light from entering the lens by changing the size of the opening.  After all these years, we still use the term “stop.”

And with that tidbit of info, I am all the more grateful for our modern technology – imagine hauling metal plates everywhere with you for your photoshoots!

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.  For now, 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.  We have a triangle and work with more than just aperture because 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 in the light.  Shutter Speed does the trick rather nicely.  A great example of this is when creating a Starburst in your photos. 

A little side note about starbursts and aperture blades

When you create a starburst in your photo, pay attention to the number of stripes, or flares, you see on the starburst.  Every lens creates a different starburst look, and here’s why.  Starbursts result from how many aperture blades are in the lens and the shape of those blades.  An odd number of aperture blades will create double the number of stripes, wherein an even number of aperture blades will produce the same number.  Even-numbered aperture blades will also make longer stripes of higher intensity.  Finally, the starbursts will be shaped uniquely according to the shape of the aperture blades.

Now that I’ve got you thinking about starbursts take a look at Capturing A Perfect Starburst Is Easier than You Think for my best tips on how to achieve this look in your images.

3 – What Controls the Aperture Blades?

The lens completely controls aperture settings.  The camera body has nothing to do with aperture. When I began learning about my camera I was confused about how the camera body and the lens controlled the different parts of the exposure triangle.  Aperture blades are in the lens, so your aperture and f-stops can change according to what lens you are using.  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 houses the aperture blades and solely controls the aperture, you can begin to see why the correct lens for the job becomes very important.  Once you understand how aperture blades work, you can then understand what situations call for more light in your camera.  Controlling aperture lets you allow light in without compensating with a higher ISO, resulting 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?

4 – What is lens aperture?

Of course, it’s lovely to know that the lens controls the aperture, but how do I know what the aperture range is for my lenses?  Knowing about your gear and what it can do is so important.

There are a couple of ways you can determine the aperture range on a lens.  If you are considering a new lens, you can check online for the item specs.  It seems pretty basic, but what if you already have a lens and would like to know the aperture range?  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.  This information shows that this lens has a 70-200mm focal range and a maximum aperture of F/2.8.

Showing specifications of specific lens

Another way to determine the aperture range of your lens 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, do your research!  It is almost always better to have a lens 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.

When you begin shopping, you’ll see 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 and create a wider maximum opening — these shifts in design call for more engineering and more expensive materials.  In short, as my dad would say, “you get what you pay for.”

You get what you pay for


5 – Does it Matter How Many Aperture Blades my lens has?

As discussed above, the number of aperture blades in your lens can make a significant difference in the creative starburst effect in your photos.  But is that the only thing to look at when considering how many blades are in a lens?

The number of blades in a lens doesn’t matter when the lens is wide open.  But when you stop down your aperture, you’ll see that the number of aperture blades in your lens will make a difference in the way your bokeh looks.  Bokeh is the dreamy soft background that happens when you adjust your depth of field.  Different configurations of the aperture blades will give you a different result in your bokeh, although most people won’t notice the difference at a glance.  After all, when using a shallow depth of field, the idea is to get your subject to pop on that creamy background so the viewer’s eye will naturally look for the subject and not the shape of the bokeh.

The short answer here is unless you are shooting for a particular effect, it isn’t all that important for most hobby photographers or beginners to buy a lens based on the number and shape of aperture blades are in the lens.  Take note that most entry-level lenses have seven aperture blades, and budget-priced and kit lenses come with five aperture blades.

As discussed above, the number of aperture blades in your lens can make a significant difference in the creative starburst effect in your photos.  But is that the only thing to look at when considering how many blades are in a lens?

Bonus Info  – F-Stops and Other Lingo About Aperture Blades

Now that you’re knowledgeable about what aperture is and how you can use it, the only thing left to learn is how to sound like a pro when talking about aperture in photography.  Just kidding, there’s always more to learn, but for now, let’s talk about the jargon with a quick summary of photography words and their meanings.

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 important to note 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 has a very large aperture.  The bigger the aperture, the more light can get to the sensor, thus allowing a faster shutter speed, hence a fast lens.

When you shoot with your lens wide open (smallest #), you are shooting with your aperture blades open as much as possible, thereby letting the most light into the camera.  You will want to shoot wide open when you would like amazing, creamy bokeh in your images.  Just remember that shooting wide open also gives you the smallest slice of focus, so use caution when shooting a moving subject. It’s pretty easy to miss focus when shooting wide open. 

Related: The 10 Photography Terms You Need to Learn Right Now

Stopped down
A ‘stop’ is a halving (or doubling) of the amount of light funneled into your camera.  “Stopping down” refers to lowering the aperture by this measure.  If you stop down your aperture, you reduce 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 #).

More info: 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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