Free Photography Class #4: All about Camera Aperture

Learn Photography for Free #4: A Beginner’s Guide to Understanding Aperture. Start by understanding our camera! Read More…

Camera Aperture explained Understanding Aperture
Camera Aperture Explained with examples

Free Photography Class #4: All about Camera Aperture

So, if you already completed the discussions up to now… You now know the general fields in photography, niches, and an understanding of a camera’s focal length.  So now, we have reached one of the most creative settings on a camera.  As we understand aperture (how wide the camera’s shutter opens to take in light), you can completely change the way the world sees your photos.  So, in a nutshell, all cameras have a minimum and maximum aperture setting.  Now, let’s get to it, your camera aperture explained.

For beginners, you typically will only look at the maximum lens aperture, or how wide the lens can open up.  The lower the number (also called an f-stop), which is displayed with an f (e.g. f 2.8,  f 4.0) the wider the lens will open.  So a camera that shows “f 2.8″ will open much wider than a camera that says “f 5.6.”  Think of things like the gauge of wire, metal, earrings, piping, this is the same idea.  Bigger the number or gauge, the smaller the diameter. 

Camera Aperture Explained, Understand aperture
Camera Aperture Explained- Understand Aperture

Camera Aperture Explained: Variable Aperture

So, the lower the number the wider the camera can open. What if the camera says it is a focal length of 75mm-300mm and has an “f 3.5-5.6″.  This is called variable lens aperture.  These lenses will typically be much cheaper than one that only shows one aperture like f 2.8.  So in the 75mm-300mm example, this means that at 75mm the aperture can be set as open as f 3.5; however, as you zoom in closer to your subject, your maximum aperture is going to change. The lens will not be able to open as much as it could at a lower focal length. 

So at 300mm the widest the lens will open is f5.6. At 200mm it might be something like f 4.5.  So if you have your camera at 75mm and set to the highest aperture possible (f3.5) as you start zooming in, you will see your camera start adjusting your aperture. If nothing else is adjusted, this will make your image darker.


Well, because as you reduce the aperture, the shutter will not open as wide. If it doesn’t open as wide, then not as much light can be let in. We will go over how to correct this later, once we start learning the settings of a camera. But for now, we are just trying to learn how a lens works. It’s also important that if you are at 75mm and want to set your camera to f8.0, then it will not adjust as you zoom into your subject more. Why is that?

Well, a variable aperture lens has limits to how wide it can open at different focal lengths; however, f8.0 is not opening as wide as any of those maximums. So if the maximum aperture at 75mm is 3.5 and the maximum at 300mm is 5.6, f8.0 is a smaller hole than both of those. In fact, if you set your aperture to f5.6 or above, your camera won’t change the f-stop at all as you zoom in and out. So if all you need is a lens to take landscape photography and you know you will always use f11.0, then maybe a variable lens is for you. Especially since you can zoom in and out and it will stay at f11.0.

Understand Aperture- A few more notes

But in the real world, you will use a lot of different apertures… So, I wouldn’t limit yourself if you have a choice. I have published and exhibited many images that were taken with a Canon 75-300mm f3.5-5.6 STM. It is a great, cheap lens for outdoor, daytime photography and typically, those maximum apertures are more than enough when taking pictures from a distance. Something to consider, at least on a telephoto lens.

All that variable aperture business above, that doesn’t apply to a lens with a single max aperture like f 2.8… you can be at 75mm or at 300mm and still set the camera to f 2.8.  Cost and weight are the real benefits to a variable aperture lens, and they are both very big differences.  I have shot great pictures on variable aperture lenses, but I typically chose them because they were around $300 to $500 compared to $2000+ (prices are an example only, both types of lenses can be much more expensive and much less expensive depending on manufacturer, aperture, focal length, features, etc.)  Unless you are strapped for cash or hike with your lenses and are worried about weight, I would not consider a variable aperture lens.  Next, I’ll explain why.

Camera Aperture Explained, Understand Aperture
Camera Aperture Explained- Understand Aperture

Camera Aperture Explained: How does it affect my pictures? 

The wider your lens can open (maximum aperture, lower the f number) the shallower your depth of field will be.  I am sure you have seen tons of pictures from professional photographers that have a really blurred background (called bokeh).  That is caused by a wide-open lens (even camera phones have learned to digitally mimic this effect in “portrait mode”). 

The wider you allow your lens to open up when taking a picture, the more it is going to capture details from your subject you are focused on and blur everything around them.  This really makes the subject pop off the page while reducing the distractions all around them.  The wider the lens opens, the more light that will come in as well.  So, if you are in a really dim room, or trying to take pictures of the night sky, you need a wide aperture to gather as much light as you possibly can. 

The Exposure triangle

Since there are three primary settings you can adjust on the camera itself that we will cover later (shutter speed, ISO and Aperture), aperture becomes one of the settings you can adjust for creative effect.  We will discuss the other settings later, but say you want to take a picture of a person with a really blurred background but it’s super bright outside, you can adjust your shutter speed to only open for 1/3000 of a second.

So even though your lens is going to open super wide and let in a ton of light to give you that bokeh effect behind your model, the shutter is only going to allow light in for a super, super, short period of time.  If your shutter was open for say, 1 full second, your picture would just come out totally white or “overexposed.”  That just means, way too much light entered your camera through the lens and hit the sensor. 

Camera aperture explained - understand aperture
Camera Aperture Explained- Understand Aperture

More Light!

In the other way, if you were taking pictures of the night sky and wanted to open up your lens really wide to try and let in all the light you can, you might set your shutter to stay open for 15 seconds or more!  If you were to set your shutter to 1/3000 of a second here, you would get a totally black image because your sensor was “underexposed,” or it didn’t get enough light to make out any details.  at the end of this blog, I provided some examples of images at different “f-stops.”  Notice that when I use f2.8 you see the top of the baseball is in focus and everything else is blurred. As I “stop up” or “increase” the f-number, you start seeing more detail all around the baseball.  Sometimes you want that! 

If you are taking a landscape picture in mid-afternoon sun and you want to show everything from the beautiful sky, some close trees, mountains or a lake in the background, you want to use something more like f 11.0 so you can capture all that detail all around instead of blurring it out.  But of course, you still have to check and make sure enough light is getting in to create your image, so you might have to decrease your shutter speed as you increase your aperture (use a lower F-number, widen your shutter opening). 

This is a delicate balance that we will discuss later and learn to do like muscle memory.  Soon you will just walk out to a scene, see your vision for what the picture should look like, and be able to get close or right on the settings you want to make that picture happen!

What maximum aperture do I need?

That all depends on the type of photography you are doing, but remember that all cameras will adjust all the way up to minimum apertures like 24-32, something like that.  The thing that makes lenses different is how wide they can open.  You are going to pay a whole lot more for a quality lens that will open up to an f 2.8 or lower.  This is where prime lenses come in as a cheaper alternative. 

I remember one of the first lenses I purchased was a Canon 50mm prime lens with an f 1.8.  That lens cost me about $125 brand new and took amazing portraits that would rival many $1000 lenses, but being a prime lens, I had to move forward and backward a lot to get the perfect “zoom” I wanted.  It’s not a bad option if you are a portrait photographer.  They are light weight, offer a lot of quality, and offer one less thing to worry about. 

Where is it now?

I gave that lens to a new photographer just starting out with professional portraits and replaced it with a 24-70mm f 2.8 that cost around $1400, but now I have one lens to cover from wide angle shots to almost short telephoto.  Perfect for close up action, portraits, low light shooting… it’s a lens I leave on most of the time because it is so versatile.  But you pay a lot more for convenience!

Still Not Totally Understanding Aperture? that’s okay!

If there is anything about this that confuses you, don’t fret!  This chapter is meant to show you the price and type of lens you may want to buy one day, not teaching you how to use it.  We will discuss that after we finish up all the nuances of cameras and lenses.  Gotta know your gear before you learn to use it right!? 

Below are the examples I talked about earlier, notice the difference in how the world around our focal point changes as we change from f2.8 to f24.0 (read the captions below each picture for details).  Big differences right!? Remember, the only real reason one lens is better than the other is that you have more choices. An f 2.8 and an f 4.0 can both be set to f 4.0, the difference is if you need that little, bigger opening, only the f 2.8 can give it to you, but it’s going to weigh and cost more to have that extra glass.  So, it’s up to you if you need it or not.

Our final section on lenses is up next! We are going to talk about things no one really tells you before you buy a lens.  Things like types of motors, image stabilization, weather sealing, filter sizes, hoods, lens mounts, then a little on lens purchasing and care.  I can’t wait to spend some money! And don’t worry, the final lesson, #10, is on mastering aperture; so more to come!


Camera Aperture explained Understanding Aperture
Taken by Seven11 Photography at f 2.8 with 100mm Macro lens at 12 inches away. Thick creamy bokeh throughout the bottom of the frame which draws the attention to the top layer of stitching. Notice you almost can’t even read the “official” writing on the bottom of the ball. Understanding Aperture


camera focal length explained comparison
Taken at f 4.0 with 100mm Macro lens at 12 inches away. Bokeh still throughout the bottom of the frame from the bottom laces down. Just slightly more detail than you saw with f2.8. Understanding Aperture


camera aperture explained
Taken at f 8.0 with 100mm Macro lens at 12 inches away. Heavily reducing the bokeh to only be in the bottom corners and maybe a little on the bottom-middle of the frame. Understanding Aperture


Understanding Aperture
Taken at f 16.0 with 100mm Macro lens at 12 inches away. Really not much bokeh at all, just some obvious softness to the bottom corners. Understanding Aperture


camera focal length explained comparison
Taken at f 24.0 with 100mm Macro lens at 12 inches away. Virtually no bokeh, just detail from center to corners (maybe slightly soft in the corners). Understanding Aperture

Need new equipment? Give KEH a try! But certified used equipment that is graded by experts. You can even sell or trade your old gear for new gear!

Photography and writing by Jon Frederick

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