Aperture is one of those terms and concepts that you MUST learn to become a proficient photographer. Basically aperture is how large the opening is that lets the light into your camera. This light is what hits the film or digital sensor to expose the photo.
Obviously the larger the aperture (larger opening) the more light that hits the sensor. Aperture is also referred to as “F Stops”, f/1.4, f/4, & f5.6 are all examples of the f-stop or your aperture. The numbering scheme is a bit confusing though. The smaller f-stop “number” the larger the aperture. Here is an example to illustrate different apertures.
In the above example you can see a much larger opening at f/2 vs f/16. In reality f/2 will let in 64 times more light than f/16. That will make a huge different when trying to expose your photo. Aperture also affects your depth of field. (more on that later)
The maximum aperture or f-stop is determined by your lens. Some lenses have only one f-stop. Some lenses change their f-stop as you zoom in and out. Fixed focal length (non-zooming) or prime lenses don’t change their maximum aperture. Most consumer grade zoom lenses
change their maximum f-stop when they zoom. Most of the higher-end zoom lenses have a fixed maximum f-stop even while zooming. You can generally see this printed on the lens itself. Look at the Canon 28-135 lens to the left. The maximum f-stop is listed as “1:3.5 – 5.6″. This means that when the lens is not zoomed in (28mm) the maximum aperture is 3.5. When lens is fully zoomed in (135mm) the maximum aperture is 5.6. So when using this lens at its’ widest angle (28mm) you are letting more than twice the light than when you zoom into 135mm.
A lens determines the minimum and maximum aperture or f-stop. Your camera body can always adjust the aperture withing that minimum and maximum. Using the same lens example you can set your camera body to use an f-stop of f/8. Then no matter how much you zoom in or out the aperture remains at f/8. Some lenses (generally higher end lenses) do not have a variable aperture. The Canon 70-200mm f/2.8 has a maximum aperture of 2.8 through its entire focal range.
Aperture works hand-in-hand with your shutter speed and ISO settings. You cannot think of one without considering the others. I will go into more detail about ISO and shutter speed, but in short, ISO is how sensitive yor sensor is to light and shutter speed is how long your shutter stays open. All three, shutter speed, ISO, and aperture, effect how much light you have to use for creating your photo.
For example if you are taking photos out at the soccer field and it’s starting to get dark, what ISO, aperture, and shutter speed are you going to use? Even if you are not shooting in manual or partial manual modes you need to understand these three measurements and what effect they will have on your photo. Let’s say you know you need a shutter speed of 1/500 or the soccer players are blurry. Your shooting on Aperture Priority at f/5.6 and an ISO of 600. On Aperture priority your camera chooses the shutter speed and you are controlling the aperture and ISO. It starts to get a little darker outside and you notice your camera in now using a shutter speed of 1/250. You know this is too slow to get a clear shot of the players so what do you do? Let’s ignore ISO for a moment so that leave changing your aperture. You want to get back to 1/500 so you need to double your shutter speed. To do that you need twice the light. Changing your aperture from f/5.6 to f/4 will do just that. Want to shoot at 1/1000 open up your aperture to f/2.8. As a beginner don’t expect to remember f/1.4 lets in 4 times the light of f/2.8. Just remember a lower f-stop “number” means more light. Adjust your setting accordingly. You will learn more about the specific numbers later. Here is another diagram showing you the f-stop and the size of the opening. Each of these f-stops lets in twice the light of the f-stop to its right.
One other topic that I want to touch on with aperture is depth of field. That is basically how “deep” your focus’s is. As a beginner it is more important to understand aperture and how it related to light, but depth of field becomes very important as you start to increase your photography wisdom. There is a lot more to depth of field than just aperture so I will save much of it for another lesson.
A large f-stop (low number) create a more shallow depth of field when compared to a low f-stop (larger number). Taking a photo of a group of people at f/2 will probably make several people out of focus since they are not all the same distance from the camera, however a photo of a single subject may be just fine at f/2. Keep in mind that your depth of field may be as shallow a few millimeters or as deep as hundreds of yards.
Generally if you want most of the photo in focus you will want to shoot at f/8 to f/22. When you want more subject isolation shoot at f/4 and below. Shooting at very low f-stops can be very challenging. I have shot at f/1.4 and had one eye in focus and one out of focus, that is how shallow your depth of field is at f/1.4. Take a look at the photo below. The top left represent an aperture of f/5.6 and the bottom right is f/2.
Let’s say you want to shoot a photo with everything in focus so you choose f/8. Now you are going to need 8 times the light vs shooting at f/2.8. Depending on how much light you have this may be okay. What if to get a properly exposed photo you need have a shutter speed of 1/10, which is pretty slow. At that shutter speed any camera shake will cause a blurry photo. Then again it may be fine because you are taking a photo of a non-moving object like a landscape photo. In that case put your camera on a tripod and shoot away at 1/10. Again there is also ISO that you can adjust, but we will save that for another lesson.
This is a beginning guide to aperture so there are more advanced items to be covered later. For now try understanding what aperture is and how it relates to light and how it is connected to ISO and shutter speed. Click on the links below find out more about how to get the perfect exposure.
- 3 Photography Concepts You MUST Learn - A brief intro to aperture, shutter speed, and ISO
- ISO – A beginner’s Guide – Find out what ISO is and how is affects your exposure.
- Shutter Speed – A beginner’s Guide – What is shutter speed and how does it relate to ISO and aperture
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Very comprehensive, possibly could be condensed down a bit though. A bullet pointed list might drive the points home faster.
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Thanks. It’s a tough balancing act. This is a beginner article, but beginners need a complete picture. Thanks for the comment.
Hi Matt, great artical which i will have to read again and again. When you do HDR photography is it the aperture that you need to change for the 3 different shots?