Aperture - What is it?
Aperture. Depth of field. The "f-stop". What are we talking about? Why do we believe that aperture is the first choice we should make in composing an image? Why do we seem to obsess over the number to the right of the "F" when choosing a camera lens?
Whether you're an experienced photographer or filmmaker, or someone with know prior knowledge of the craft, the concept of manipulating the depth of field in an image is really very simple. Capturing an image, whether on a strip of film, a memory card, or a removable hard drive, is all about controlling the reflection of light upon a subject or scene. Naturally, the scene is the first component of this process...before you can light or capture an image with a camera, you must compose the shot ("find your frame").
Once you've found your frame (set the camera at the desired angle, and positioned your subject(s) within this frame, you need to choose your aperture. Your choice in "f stop" (e.g. aperture setting) will determine how much of your frame is in focus, essentially setting the creative tone for the story you plan to tell. On top of including or excluding elements inside your frame from your final image (what is in focus will play a crucial role in what your audience extrapolates and subsequently play a critical role in how your photograph is interpreted, while what is out of focus will largely be dismissed or simply "missed"), the aperture setting will dictate the necessary shutter speed and light sensitivity (ISO) to expose properly.
Hopefully you're beginning to understand how important aperture is in storytelling, but if it's vague or anything less than clear, let me restate it:
The aperture at which you capture an image will not only directly impact the message your audience takes away, but will influence the speed and sensitivity at which you capture the image.
Aperture & the Exposure Triangle
The Exposure Triangle may seem complex at first, but it's really as simple as "one, two..three". The three points of the triangle represent the three settings involved in setting exposure, the term used to represent the collective process of capturing an image in photography or cinematography.
I suppose more space on this page could be taken up to break down the term exposure, but if you're here, on the Cinematic Spirit blog page, reading through a post focused on Aperture, I'm going to assume you have at least a basic working knowledge (or a burning curiosity) of photography, and spare you the deep dive into the term. That being said, let's begin.
In the photography world, aperture is the size of the opening between the blades inside of a camera lens. The setting (size) of this opening controls the amount of light that passes through a camera's shutter, first and foremost, determining the depth of field in a given image, as well as shaping the requirements for time (shutter speed) and light sensitivity (ISO) when capturing a properly exposed image. Aperture is described in terms of the "f stop" (f11, f2.8, etc.) in photography, and can be measured via simple inverse correlation to the number found beside the "f". A high f value (f11, f16, f22) represents a very small aperture opening, while a low f value (f4, f2.8) represents a large, or "wide" aperture.
f2.8 is a wide aperture (the opening is very large)
f11 is a narrow aperture (the opening is very small)
Picture a cat's eye. In the dark, or absence of light, the pupil enlarges. This is an example of a large aperture, or opening, letting in more light in order to grant our feline friend the ability to see in dark situations. What is perhaps less obvious, is that this enlarged pupil (enlarged opening) will see only those things within a short distance, at least with full clarity. During the daytime, however, there is an abundance of light, perhaps even too much light. In situations with an excess of light, the pupil decreases in size, just as our aperture will need to decrease in size, in order to mitigate the amount of light so that the kitty (or our camera) can see clearly what lies in front of it. As you can imagine, this has the opposite effect on depth of field; a small aperture (high f stop) will not only decrease the light intensity in your frame, but extend the depth of field to a further distance.
To clearly state the implications of the previous paragraph, let me speak bluntly:
A high f stop (narrow aperture) is necessary to achieve a photograph in which all (or most) elements of the frame are captured in focus and with a high level of sharpness or clarity.
A low f stop (wide aperture) is a tool we can use to eliminate distraction or direct the viewer's focus to a single (or small group) of relevant elements within an image. Our target subjects/features will remain in focus, while elements in front of or behind the targets will be blurred, essentially removing them as key elements of our story.
Aperture is your tool. Nobody can tell you how to use it, because nobody is you, and nobody has control over your creativity. That being said, I urge you not to fall into the trap of shooting everything "wide open" (f1.4, f2.8, etc) simply to achieve beautiful bokeh or create a dreamlike feeling for the viewer. These type of shots have their place (weddings and portraits, primarily) but are often overused or relied on as crutches by photographers and "videographers" who lack the experience or courage to compose a frame in its entirety, and take the time to arrange or modify elements in the background/foreground while still maintaining their desired aesthetic in relation to the subject(s).
If you need proof of what I'm about to say, just hop over to your favorite streaming entertainment platform and watch a feature film (movie) with a large production budget (e.g. something that hit the theaters, not your friend's short film that won awards at local festivals, or your favorite wedding videographer's demo reel). Cinematic images (still or moving) always have a moderate to high depth of field.
The majority of television and motion pictures you watch are shot at f stops of f8 or higher, with the exception of sparingly used shallow images, typically focused on a single character, interaction, or important element of a scene.
Shutter speed is, well, exactly what it sounds like...it is the speed at which the shutter on a camera operates (opens and closes). In photography, this relates to the opening and closing of the camera's shutter when the user operates the shutter button (e.g. takes a photograph). In cinematography, it relates to the speed at which the camera captures continuous frames as it is "rolling" or recording.
A high shutter speed is necessary to capture objects in motion without "motion blur" (I feel like I don't need to explain that term, if I'm wrong, I'm sorry...it is what it is...blurred motion), and a slow shutter speed is only necessary when creating images with intentional blur or showing the passage of time in a creative manner, such as light painting.
ISO or in traditional photography, "film speed" is a term used to describe the sensitivity of film to light, and its values were set by the International Organization of Standards, and eventually adopted by the filmmaking community at large. The relation between ISO numbers (ex: ISO 800) is characterized by a positive correlation between the ISO value and the sensitivity to light of the film (or today, digital media) inside a camera. ISO is the last value in the exposure triangle that you want to adjust. In other words, setting your exposure goes like this:
- Choose your depth of field (Aperture)
- Choose an appropriate Shutter Speed
- If you don't have enough light (or didn't bring one with you) increase your ISO
The lower your ISO number, the cleaner your image will be, in terms of Noise, or Grain. Yes, grain can be used intentionally to enhance the emotion in a given scene (a flashback to a previous time in a character's world, a dream sequence, or a gritty scene), but typically you'll want to capture images with as little noise (grain) as possible. This is why learning to work with artificial light is so important. A natural light photographer is forced to increase their ISO when shooting with an f stop and at a shutter speed that fail to allow adequate light into the frame to create proper exposure, while a photographer who is experienced with flash and continuous lighting has both at their fingertips to mitigate this problem.