Photo 101: Aperture

The basics of photography involve something called the Exposure Triangle. The exposure being your photograph, and the three points of the triangle being the following: shutter speed, ISO, and aperture.

Shutter Speed is the amount of time that the camera’s shutter is open and letting light hit the sensor. It is usually a fraction of second. The faster the action is, the faster you want the shutter speed to be. Photographing sports? You’ll want a shutter speed of something like 1/500, or maybe faster. Photographing friends and family at a gathering? A shutter speed of 1/125 will probably do the trick. Want to make that water look silky and flowy? A shutter speed of a few seconds will do that. And if you’re in the middle of nowhere at night and want to photograph star trails? You’ll need a few hours for that.

ISO, in a few words, describes how sensitive the sensor is to light. It really describes how much the camera has to amplify the signal as it’s going from the sensor to the processor. Isn’t that nice and technical? What you want to remember about ISO is that the lower the number is (say, 100 or 200), the cleaner the image will be. The higher the ISO (3200 or 6400), the faster the camera will work in low light, but it means the picture will appear grainy.

I’ll go into each of these in more detail later, but today’s subject is the aperture.

Aperture is the opening at the back of the lens that opens and closes to allow light into the camera. It works like the pupils in your eyes. In a dark room your pupils widen to let more light in. In bright light, your pupils constrict to let less light in. Aperture also controls the depth of field.

What’s ‘depth of field’? It describes how much of a photograph is in focus. When you look at a portrait where the person’s eyes are in sharp focus but everything behind them is blurry, that photograph has a shallow depth of field. And when you’re looking at, say, and landscape where everything is sharp and it looks like you could walk right into it, that photograph has a large or wide depth of field.

For example:


I photographed my cat using an aperture of f/1.8. Because I focused on his eyes, they are nice and sharp, but the farther to go from his eyes, the blurrier things get. His ears are starting to blur out, and his body and the bookshelves behind him are completely blurred. This is due to the f/1.8 aperture.

08_12_2017 Iceland 282

This photograph displays a wide depth of field. The waterfall was about fifteen feet in front of me, the mountain was miles away, and the snow-capped volcano peeking around the left side of the mountain is miles behind that. But everything is in focus. In this case, I used an aperture of f/16. The shutter speed dropped down to 1/13 of a second (that’s why the waterfall looks that way), so I had to use a tripod. Remember that the smaller the aperture is (f/16 or f/22 for example) the less light will be coming in.  If landscape photography is something you want to get into, you’ll definitely want to get a tripod.

Now, aperture goes by a couple of different names. You’ll hear it called just ‘aperture’, and you’ll also hear it called F-stop. They’re the same thing. In video, you might hear it called T-stop, which is a similar term but measuring a different thing (F-stop is measuring the focal length of the lens versus the diameter of the aperture, while T-stop deals with the actual transmission of light. Confusing? Yeah, but you don’t need to worry about it unless you want to get super duper technical).

Aperture is expressed in text as f/n, with ‘n’ being the aperture, like f/1.8 or f/22. If you want to start learning how to control the aperture and your camera has manual settings, turn the camera’s mode to A or AV. Both of these are for the Aperture Priority mode (the AV is specific to Canon cameras, and stands for Aperture Value). This will allow you to set the aperture while the camera sets the shutter speed for you. It’s a useful way to see how adjusting the aperture will affect the shutter speed.

Here is an example of how adjusting the aperture affects your depth of field. In the photos below, I focused on a rose in the lower left. As the aperture changes, you’ll see more of the background come into focus:













Remember, the lower the aperture’s number, the shallower the depth of field will be. And because photography’s terminology is weird, a low aperture number means that the aperture is wider and so will let more light in. This is great in low light situations, but can cause the photo to be too bright in, say, daylight. Like anything else, it takes practice to find the right balance for your exposure, so keep practicing. You’re working with digital cameras, so you can take as many photos as you want and delete the ones that don’t turn out.

A few quick notes regarding aperture and depth of field.

Thanks to their smaller sensors, phone cameras and point & shoot cameras have a hard time with shallow depth of field. Unless you are close to your subject and your subject is far from the background, just about everything might end up in focus. Some phone cameras have the ability to blur out the background after the fact, but blur caused by lens and aperture looks different from blur caused by software. But if you like the effect of blur from software, carry on.

Also, if you’re using a wide angle (to get a lot of things into the picture, like for landscapes or group pictures) there might not be a lot of background blur. The wider the angle of the less, the less blur there will be. If you use a telephoto lens (like you might use for photographing things that are far away), you’ll get more background blur. The trade-off is that you will have to be farther away from your subject.

And finally, bokeh. You might have heard the term tossed around before, but don’t know what, exactly, it means. Bokeh (BO-kuh) is a Japanese term that doesn’t have an exact English translation, but it essentially means, “the quality of the blur”. Photographers will spend a lot of money on lenses that produce the most aesthetically pleasing blur because when it comes to making compelling photographs with a shallow depth of field, attractive blur is essential to the appearance of the photograph as a whole.

2 thoughts on “Photo 101: Aperture

  1. This was awesome!! Omg I’ve never gotten a better understanding of f stop! I never know what to use for what I want to accomplish but this is great. I need simple and example!thank you!!

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