Many photographers are familiar with the golden triad of exposure compensation: shutter speed, ISO, and camera aperture. Together, these three are the artist's first line of defense when working in the field.
While the shutter speed determines how long the entrance pupil of the lens stays open, aperture is a measure of how widely the hole is held during this interval of time.
Camera aperture influences the quality of the image intimately, imparting a very different personality depending on how it is used to manipulate the image.
What Is Aperture?
In the front of any lens, there is a hole called the camera aperture. It is used to control how much light is allowed into the camera. Fanning blades dilate as the artist opens it, and close as the artist shuts it.
The wider that you hold the aperture open, the more light falls through, and vice versa. Much more than the exposure of the image will change with this value, however. Let's go over how aperture affects your photos.
Depth of Field
The plane of photography corresponds to one infinitesimally thin focal plane in front of the camera. This slice is the part of the image that is clearest and most in focus; it moves closer to you and further away as you adjust your barrel.
The focal plane is scantest when the camera aperture is widest. As the aperture closes, the slice takes on volume and can enrobe a subject of dimension fully, bringing the entire person or object into focus at once.
The size of the aperture should be one of the first things to consider when composing the image around whatever you want to be in focus. It's the difference between the tip of the nose and the entire face being captured perfectly.
A tight aperture will produce a razor-sharp image, and this effect carries on to some extent, even as you move outward from the heart of the focal plane.
No lens is capable of keeping everything in front of it in perfect focus at once, not even one with the narrowest aperture possible. But still, the smaller the aperture, the cleaner things are going to look in a general sense.
When you would like every detail to ring loud, clear, and true, shooting with a smaller aperture is a safe bet in the same way that a low ISO and a fast shutter speed will also protect you from marring the image in the heat of the moment.
At the other end of things, a larger lens aperture will result in a slightly softer, more diffuse look.
A wide aperture can capitalize on every possible source of bokeh, one of the most visually appealing effects that comes with a wide aperture. Changing the aperture increases or decreases the circle of confusion accordingly, impacting the size of each bokeh on-screen.
How Is Aperture Measured?
As the diameter of the camera aperture widens, the number used to describe its gauge decreases. A very small aperture would be something like an f/22, while one that is open wide would be something closer to an f/2.8 or f/1.4.
This number, called an f-stop, is used to break down the range of possible diameters so that an increase of one f-stop will always either double the amount of light being let into the camera or cut it exactly in half.
The same consideration is taken with shutter speed and ISO, such as when increasing one's ISO from ISO 800 to ISO 1600. All of these exponential leaps increase proportionally, and at the same rate. This provides a common language for all three of these different factors to be dealt with in.
The scale of f-stops is not totally universal, but some common ones include f/1.2, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, and f/64. F/4 is regarded by many as the sweet spot for a variety of practical types of photography.
But most modern DSLR photographers will feel totally comfortable shooting at an f/2.8 or even an f/2. It all depends on your needs, and perhaps how steady your hand is.
When Is It Best to Use a Narrow Aperture?
The smaller the aperture, the more likely you are to get a legible image. A narrow aperture disciplines the incoming light and allows less room for "error." When the focal plane occupies the entire volume of space in front of you, it lessens the need to ride the barrel as you follow your subject through the scene.
Here are some scenarios that would justify a narrow aperture.
One of the perks of working in a studio setting is having complete control over how it is configured.
Indoors, even something like a 1K fresnel or a cheap strobe will be enough to support a very narrow aperture. Definition and integrity are easy to achieve when working this way. This is made doubly true by the freedom that you have to mold each source of light around the subject as you shoot.
When shooting something huge like a mountain at sunrise, there usually is no need to separate the majesty of the subject from the background. Many prefer to see the entire scene in crystal-clear focus. A narrow aperture is much more capable of seeing everything in front of it at once.
When Is It Best to Use a Wide Aperture?
The look of a photo shot with a wide aperture is one that many artists prefer and seek actively. While not always the way to go, it really is easy on the eyes when done well and at the right time.
Let's go over when you should use a wide aperture.
Shooting in the Dark
When light is scarce, wide aperture photography provides the artist with the means of producing a sufficiently exposed photo under a variety of conditions.
If you're shooting methodically or with the help of a tripod, you will likely be able to get by. Both of these things will help stabilize the image, counteracting the softness that wide aperture photography confers.
Portrait photographers will usually invest in prime lenses that offer a very wide maximum aperture. The subject is suspended in a bonafide snowglobe that cradles them without distracting the viewer with unnecessary surrounding detail.
When shooting a portrait, your subject is the star of the show. A shallow depth of field acts like a spotlight that lets them shine.
When shooting for yourself, there are no rules. Follow the subject's lead and you will rarely be led astray. If your gut is telling you to go wide, we advise that you take heed.
Choosing the Right Camera Aperture for Every Occasion
The right aperture to choose? One could say that it's already right in front of you.
Terrible jokes aside, you'll be glad to know that a worthwhile final product will rarely be out of reach, even if your lens isn't the fastest. If you've got your wits about you, you'll be able to work around anything that you run into.