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Camera Basics: Aperture (or focal-ratio, f-stop)

Post requested by a dear friend, K, regarding camera basics (namely aperture). A few other camera basics posts will be coming up in the next few weeks covering topics like ISO, white balance, composition, etc. Please keep in mind that this is a BASIC review – for more information, either send me an e-mail or comment to request something more in depth.

I could go into a long definition, but I’m going to keep it simple as there are plenty of other resources that will give you a more lengthy answer. Think back to pinhole cameras – literally a box with a hole in it (the hole let in light that hit the film in order to create a photograph). The hole is the aperture. Nowadays with digital cameras, you’d probably recognize aperture by the following numbers: 4, 5.6, 8, 11, 16, 22. It ranges anywhere from 1.2 (sometimes 0.8 even) to 32 – rarely above or below that range (starts to cause issues).

If it’s easier, think of the camera as an eye. The camera body is the brain, the lens is the lens, and the aperture is the size of the pupil. When you walk into a dark room, your pupils dilate – why? To let in more light so you can see better. When you walk into a bright area, your pupils constrict, to let in less light. Keep this in mind for the next section.

The larger the number, the smaller the aperture – confusing, right? Think of it as (1) ONE, as a whole. Then put the aperture UNDER one, so it creates a fraction. Therefore, 1/4 would be larger than 1/22, correct? Therefore, f/4 (or an aperture of 1/4 or 4) is larger than f/22. With a smaller hole, less light is let in; with a larger hole, more light is let in.

Basically, aperture controls the amount of light that is let into your camera. It also controls your DEPTH OF FIELD, or how much is in focus in your photograph. Ever notice that when you take a picture of something really close (macro), that only parts of it are in focus… and when you take a picture of the scenery (wide), lots of it is in focus? That’s the basics of depth of field – which is a whole different post. By controlling your aperture, you control your depth of field.

Why, yes I can help you. Let’s go back to the eye example, because everyone that is reading this has their eyes handy, correct?

The best example for large aperture, less depth of field is: when you’re in a fairly well lit situation – now go look at a clock (preferably analog) – or, really, anything near you. If you really, really focus on that one item… notice how other items that are nearby go out of focus? Larger aperture (smaller number) equals less depth of field.

Now squint. By squinting, you’re essentially “closing down the aperture” (smaller aperture, larger number). See how much MORE is in focus? It does get slightly darker, since you’re letting in less light, however things become more clear. Smaller aperture equals more depth of field.

Now, if you’re in the dark and you squint, since it’s already dark, you’ll probably be able to see less since you’re cutting out TOO much light. However, if you look at a bright light in the dark and squint, you’ll be able to see more.

Fun, huh?

1. Again, the camera functions much like an eye. You see things right-side-up, but the camera (and lens) sees it upside-down. The image is flipped in camera so you can see it right-side-up when you go to view the image.

2. For something in real life to be the same size as it is when captured (in a photograph), it needs to be the same distance away from the lens as the lens is to the sensor, a distance which is known as 1:1, which will yield a “true to life” size. Especially important in macro photography.

3. If you want to make a pinhole camera, experiment with a few factors: the size of the box (which could change the size of the film you use), the distance between the lid (with the hole) and the back and the size of the hole. That’s REALLY the best way to learn about aperture hands-on, but it’s not always the most practical way of learning in this busy-busy world.



*The photos were desaturated to really bring the attention to the depth of field, versus color or any other distracting elements. Instructional, not particularly aesthetic.

The top two images were taken at f/1.4 – you can see how shallow the depth of field is. You can either see the tip of the nose or you can see the eyes, one or the other. Shallow depth of field can be a great ally, especially if you’re taking portraits or have a busy background (lots of people walking around, a fence behind you, etc) and just want to blur it all out. It’s excellent for if you want to highlight part of the photograph and to melt everything else away.

The bottom two images were taken at f/8 – and see how much more detail you can see. The nose goes slight out of focus when you look at the eyes, and vice versa, but nothing even close to what f/1.4 does to a photograph. More depth of field is great for product photography (don’t you want to see all of the detail on that pair of shoes that you’re eyeing online?) or group photographs, to make sure that you can see everyone, even if there are three rows of people.

Anyways, I hope this helps! As this is my first post of this nature, any input would help me help you.

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