Of the basic settings that our cameras have, potentially the easiest to get creative with is the aperture of your lens. Today, let’s take a look at five simple ways you can make creative images using your aperture.
Before we get started, it’s important to know what the aperture is and how it works. Inside most lenses, you will find a set of “blades” that can be opened and closed to form a larger or smaller opening for light to pass through. It stands to reason that a smaller opening would let in less light than a larger one for a given exposure time, but this isn’t the only effect that it has on the resulting image. By definition, the aperture is nothing but an opening. However, it is the varying size of this opening that allows us to control so much in our photography.
Let’s jump in and look at some of the simple effects we can create by varying our aperture, starting with the simple uses.
Deep Depth of Field
First up, we can use our aperture to get more in acceptable focus. By “stopping down” or setting a higher f-stop, we can ensure that more of the resulting photo is in focus from front to back. The higher the number, the narrower the aperture, and the more of the scene that is in focus.
Especially with wide-angle lenses, we can get almost infinite depth of field. In fact, we can use something called the hyperfocal distance, we can get the most sharpness possible throughout the whole scene. There is a little mathematics involved but, luckily, apps like DOFMaster will do the job for you.
Although it may seem like going straight to your lens’ minimum aperture of f/16 or f/22 may seem like a great idea for depth of field, it may not result in the sharpest image because of an effect called diffraction. Although it varies from lens to lens and sensor to sensor, as a basic guideline, you may not get the full sharpness your lens is capable of when it is fully stopped down.
Shallow Depth of Field
What about the opposite? Of course, opening your aperture as wide as it will go reduces the amount of your scene that is in focus, especially with longer lenses. By using an aperture like f/1.8 on an 85mm lens, you will get very little in acceptable focus. Things in front of or behind the plane of focus will render very softly.
This effect is amplified by focusing closer. So, if you put your subject just a meter away and focus on them, everything in front or behind will be completely out of focus. At this distance, even an aperture of f/4 or f/5.6 on an 85mm lens will result in a very narrow depth of field.
Just like using very small apertures, using very large ones can often lead to diminished image quality. Again, this varies from lens to lens and sensor to sensor, but you’ll likely see a softer rendering and more aberrations like purple or green fringing around high contrast transitions. Look carefully at the title image in this article for an example of this.
As I mentioned in the beginning of this article, a smaller aperture allows less light to strike the sensor. In order to get the same exposure after narrowing your aperture, you need to compensate for the reduction in light. This can be done by increasing your ISO or lengthening your shutter speed. The narrower your aperture the longer your shutter speed needs to be. You can use this to your advantage.
Let’s say that your current lighting situation allows for an exposure of 1/15 of a second at f/1.4. If you stop down your aperture to f/11, you will need a shutter speed of four seconds to get the same exposure you had. This gives you the ability to blur motion in your scene. Just remember to stabilize your camera if you’re working with long exposures.
I mentioned before something called diffraction. Although it can result in undesirable loss of image quality, it can also result in some interesting effects with pin lights (lights that are effectively infinitely small). You may have seen the sun turn into a starburst or streetlights in a cityscape that render as stars. Those are the effects of diffraction and are directly a result of your aperture.
When stopped down, even the most rounded of aperture blades do not overlap in a perfect circle anymore. They form sharp edges where they join, and light hitting the edges of these points renders as stars on the resulting image. This effect is easiest to achieve with many wide-angle lenses. So, take out you wide-angle and stop it down to f/11 or f/16 to see the results. You’ll notice that every lens renders these stars differently, so experiment with all your different lenses.
Shape Your Flares and Ghosts
A couple of lens aberrations that can be controlled to varying degrees with your lens aperture are flare and ghosting. When you point your lens into a bright light source like the sun, you may see a reduction in contrast and even odd shapes forming over your image. These are flare and ghosting.
A common thing you will see between all lenses, however, is that stopping down reduces flare and ghosting, but also changes the shape of the ghosting. So by changing your aperture value, you can affect how these are rendered. Notice how at f/1.4 lights can gain an almost halo-like appearance, but when you stop down this reduces and even creates the stars we talked about above? Again, each lens is different, so experiment.
So, as you can see, this one simple control has so much potential to change the way your image looks. Consider your aperture one of the tools you have to tell the story you want to tell. If your story needs blur or flare to complete it, you can use your aperture to modify the look of both of those things. There are many other considerations like sharpness, contrast, and aberrations that go into choosing your aperture, so make sure you test your lens and understand how these things work as well. Most of all, have fun and be creative.