The Basics: Aperture

//The Basics: Aperture

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If the lens is considered the eye of the camera then aperture must be the pupil. Ok, that is a little silly but it’s a really good comparison. Aperture is the opening and closing of the lens to allow more or less light through. What happens when you go from outdoors to inside a movie theater? Your pupils get HUGE. This is because your pupil needs to allow more light in faster so you don’t trip and fall. The same is true with your camera lens, if you open up the f-stop really wide to something like f/2.8 then it is going to allow a lot of light in really fast. If you close down the f-stop to something like f/22 then it is going to let in a small amount of light slowly.

Wait, wait, wait……now I’m really confused. First you were talking about aperture and now you’re talking about f-stop. What the heck is going on?!?!?!?! Hehe, they are the same thing. The words f-stop and aperture are interchangeable. Different people will use different terms. They mean the same thing so choose which one sounds coolest to you and run with it. Just don’t get confused if someone else uses the other term.

Ok, ready to get this figured out? Aperture….I mean f-stop…..just kidding. Really though, aperture can be confusing for a few different reasons and that is why we wrote this article. Multiple names is one. Another is because a small f-stop number means a big opening and a big f-stop number means a small opening. Typically aperture ranges from f/1.2 (really big opening) to f/29 (really small opening). Apertures are specific to the lens that you are using, your camera has nothing to do with it. Here is an image to help you visualize the f/number in relation to the size of the opening.


Lenses are defined by their biggest aperture opening…..this is also described as the speed of a lens. If you have a lens that opens up to f/1.8 then that is considered a fast lens since it can allow a lot of light in very fast. Normally the faster the lens the more expensive it is. Lastly, some zoom lenses have aperture ratings that vary based on your focal length. These are typically less expensive lenses. An example of this would be an aperture range of 3.5 – 5.6 where the lens can go to f/3.5 at 18mm but can only go to f/5.6 at 105mm. More expensive lenses may have a single maximum aperture through the entire focal length. An example of this may be f/4 from 70mm to 200mm.

If you already read our shutter speed article you may remember the answer we get when asking students what shutter speed is used for. If not, let me remind you because we get the same answer about aperture. Students often say it allows more light in…..and we say YES!….but that is not the answer we were looking for. What we are looking for is what it is used for creatively. The answer to this question is: It controls your depth of field. What does that mean?

To really simplify aperture you only need to remember this one thing: LITTLE NUMBER = LITTLE DEPTH & BIG NUMBER = BIG DEPTH. That’s it!!!

Have you ever seen an image where a part of it is in focus but the rest of it looks blurry? That was depth of field control by the photographer. The smaller the f-stop number (bigger opening) the shallower the depth of field. Smaller numbers would be considered anything from f/1.2 to f/6.3. Here is an example shot at f/1.8. The tombstone of the legendary Rabbi Mordecai ben Abraham Benet on the Rabbinic Hill at the Jewish cemetery in Mikulo, Czech Republic. The large Jewish cemetery in Mikulov is one of the most significant monuments of its kind in the country. The first funerals after the establishment of the local Jewish community date from around mid 15th century. The oldest survived tomb stone dates from 1605. In this image, people leave letters and prayers to the Rabbi. As you can see the letter is nice and crisp while the rest of the image is blurry. Notice how your eyes are drawn to the letter. This is because of the composition & the use of aperture.

What about those really beautiful landscape images with flowers or rocks in the foreground, trees in the middle of the image and mountains in the far distance and they are all tack sharp? Again this is depth of field control by the photographer. They were probably using an f-stop between f/16 to f/29. Here is an example shot at f/16. This is the iconic Valley View in Yosemite National Park. As you can see the entire image from foreground to background is completely in focus.

The middle stops in a lens are typically the sharpest and the extreme open and closed apertures can get a little softer in focus. Middle stops would be something like f/8 or f/11.

Lastly, lets really bring this all together by taking a look at a range of images of the exact same subject shot from wide open to a very small opening.

f/1.8 (Little Number = Little Depth): 





f/22 (Big Number = Big Depth): 

We would love to hear from you. Let us know if you have any questions and/or how you have used aperture to create your images.

BONUS FOR THE SUPER NERDS: The mathematical equation for f-stop is N=f/D. Basically it is the relationship between the focal distance of the lens and the diameter of the opening in the lens. Equation translation: Your f-stop (N) is equal to your lens focal distance (f) divided by the diameter of the lens opening (D). For example, if you are shooting at f/4 and your focal length is 100mm then your lens opening is 25mm in diameter. NERDs Rule!

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