Steve's Photography Tips: Understanding Aperture

Since our last Photography post looked at ISO speed, let’s next talk about aperture.

First off, here is some boring technical stuff: What is aperture? In a camera, the aperture is the hole in the lens through which the light passes to get to the film (in film cameras) or the sensor (in digital cameras). The shutter blocks that hole until the shutter button is pressed, opening the shutter so that light can pass through the aperture. Much like the iris in your eye, the aperture can be opened up wider when there is less light or closed smaller when there is more light.

The size of the hole is controlled by the aperture setting. The aperture setting is represented by a series of numbers known as f-stops, and although it is confusing, the numbers are probably backwards of what you would think they would be. Because the larger the f-stop number is, the smaller the aperture opening is. Crazy talk, right? The reason for that is that the f-stop number is actually a ratio of the focal length (basically the length of the lens) to the aperture diameter. So from some simple math rules, as the bottom number of the ratio gets larger (or the aperture gets wider), the ratio number itself gets smaller. Don’t blame me - I didn’t make all that up.

So you may have seen those aperture settings on your camera. They are usually numbers like f/2.8, f/11, f/16, f/22, and several numbers in between. Sometimes you will see even lower numbers (indicating wider apertures, remember), such as f/1.4 or f/1.8. Those usually are only found on lenses that are known as “prime lenses,” or lenses that just have one focal length and don’t zoom.

What Does It All Mean?

So why is aperture important, you might ask? Good question. Obviously, as stated above, the aperture setting is important for letting the right amount of light into your camera. That makes sense. But the aperture setting also creates some interesting effects in your photos, which can be useful in artistic ways. The aperture setting can be used to create “bokeh,” or blurry out-of-focus parts of the photo. Sometimes that is desirable, and sometimes it isn’t, depending on the effect that you are going for. So it is good to know which setting causes what for those times when you want to use it.

Here are the basic rules to remember:

• Small f-stop number = wide aperture = more bokeh
• Large f-stop number = small aperture = less or no bokeh

And that’s pretty much it in a nutshell. Of course, you might want to practice a bit with it to make sure you understand it all.

Photo Examples (With Bokeh)

Want to see some examples? Of course you do! So here you go:

This first photo was taken with an aperture setting of f/11, which is pretty much middle of the road. If you are wondering, that is a figure of Maui found all around the Polynesian Village Resort at Walt Disney World, in front of several other figurines and such that are found on my desk. Don’t judge me by what I have on my desk, okay?  And no particular significance to using him, except that he looks rather happy.

Anyway, as you can see, Maui is in sharp focus, but Oswald, the Rocketeer, chubby Mickey Mouse Vinylmation, and the rest off in the background are slightly blurry. This was due in part because of the closeness of the camera to Maui with the other things in the distance, but also due to the aperture setting.

So let’s use a different setting:

This time around, the aperture was set at f/22, which was as small as the aperture on this particular lens would go. Comparing it to the previous photo, you can see that the background guys and the flag at the right are much more in focus than before. Perhaps still slightly blurry, but much clearer than in the f/11 photo.

Now let’s go in the opposite direction:

This photo used the setting of f/1.8, which was as wide as this particular lens would go. As I mentioned, you usually only find that setting on a prime lens, and that is what this lens is. And as you can see, the characters in the background are almost indistinguishable. You can tell something is back there, but you really can’t tell what any of it is. But Maui himself looks to be in sharp focus, partly because of the contrast with the blurry background. It might look like he is farther away from the background things than before, but I can assure you that nothing moved.

Here are two more examples. This first one takes advantage of the bokeh created by the lens:

See how the greyhound almost seems to leap out of the monitor at you? That’s due to the f/1.8 aperture setting here.

But then sometimes you want everything to be in focus:

For wide angle shots, such as this one of the Boardwalk at Walt Disney World, you usually want the entire frame to be in focus, because with a wide angle you are usually wanting to get as much in the frame as you can. So for scenes like this, a medium setting is better, and for those I usually use f/9 or f/11. Wide enough to let in a fair amount of light, but small enough to keep everything in focus most of the time.

So as you can see, the right aperture setting can make your subject stand out from its surroundings in a pretty effective way, or it can keep your entire photo in focus. But that’s not the only advantage.

Low Light Photography

A larger aperture opening (or lower f-stop number, remember) can also be advantageous for low-light photography. Because the larger the aperture opening, the more light entering your camera.

Take for example this photo from Bangkok:

As we were walking down this street, it was well after dark. Yes, there were some lights from the street vendors on either side of the street, but that was about it. However, thanks to the f/1.8 aperture on my camera lens, I was able to get a pretty good photo.

The same goes for this recently-featured photo from the Disney Cruise Line’s Disney Dream:

Again, the f/1.8 aperture helped to capture the nighttime scene without the use of a tripod, using the available light from the fixtures along the ship’s wall.

However, there are definitely times when a longer exposure using a tripod is more appropriate. And for those, it is better to go with a higher f-stop number, or smaller aperture. An example of this would be this nighttime shot from Pickwick Landing State Park:

The smaller aperture opening creates the starlight effect of the lights on the pier as well as along the bridge in the distance. That effect isn’t present in photos with larger aperture settings. And if you are already using a tripod, it doesn’t really matter if your exposure time is 1 second or 10 seconds, since you aren’t having to hold the camera still anyway. So go ahead and dial that aperture down, even if it does increase your shutter speed.

Put It Into Practice

So what do I do? It depends on what I am going for, which actually sometimes just depends on my mood at the time. For a few years, I almost exclusively used a wide angle lens, so I used a medium aperture setting. Lately, I have done more prime lens shooting, enjoying the effects of the f/1.8 setting on the 25mm prime lens that I have for my Olympus E-M10 camera.

I will talk more about shooting modes later on, but I usually use the Aperture Priority setting (noted by an “A” on the dial on most cameras) to have control over the aperture setting, allowing the camera to choose the shutter speed based on what I have the aperture set to. That way, I am able to make sure that I get the effect that I want.

Hopefully, this look at aperture settings has been eye-opening. Okay, so that was a bad attempt at a joke based on how the aperture works like your eye. Get it now? No? Never mind.

Anyway, feel free to leave a comment below if you have any questions or other tips! And be sure to check out other Photography Tips, too!