Summary
- Exposure is the exposing of a digital sensor (or film) to light which then allows for the generation of a photograph.
- Exposure is controlled by adjusting settings for three things: ISO, Aperture, and Shutter Speed which are often depicted in the “exposure triangle.”
- ISO represents the sensitivity level of the sensor (or film). Higher values increase exposure but also increase noise.
- Aperture represents the size of the opening in the lens. Higher values represent a smaller opening and reduced light exposure. Lower values (wider openings) produce a shallow depth of field (focus) and higher values (smaller openings) produce a deep depth of field.
- Shutter speed represents the amount of time the shutter is open and letting light in to the sensor (or film). Short shutter speeds (less than 1/500 of a second) can be used to freeze motion (think sporting events) whereas long shutter speeds (more than 1/8 of a second) can be used to capture motion blur (think dreamy waterfalls).
- Adjusting any one of the three to darken the exposure will require you to adjust one of the other two in order to increase the exposure value to proper brightness.
- Keep ISO as low as possible and let one or both of the other two settings take priority depending on your choices for depth of field and motion.
- To adjust these settings, find your camera’s full manual mode (M), “Pro” mode (some phones), or download a top-rated pro camera app (other phones).
Introduction
There are a number of things you can do to get better photos: understand your camera better, understand some basics about light, study and learn about composition, have a clear idea of the meaning and subject in your photo. Getting a better camera isn’t likely the answer; the one you have is probably just fine. Let’s start with getting to know your camera settings better. I’ll cover some of the others in future blog posts.
If you want to take better photos you have to take control of your camera. Why? You camera’s “auto” modes make assumptions when choosing which camera settings to use. These assumptions are often not the best for the subject you’re shooting or the shot you’re going for.
When you take a photo you are exposing either film or a digital sensor to light for a certain period of time. The particles of light (photons) are absorbed and either directly alter the surface (film) or are converted to electric signals and interpreted by a computer to produce a digital image.
Many cameras have a light meter that measures the light in front of the camera and tells you whether it thinks your image is too bright, too dark, or just right. Our electronics have improved to the point that you can typically judge this by just looking at the screen (including your phone camera).
Exposure Triangle
The three main camera settings determine how much light gets to the sensor. They make up what is known as the exposure triangle and consist of Aperture, Shutter Speed, and ISO. You have to decide (or let your camera decide) which combination of these three settings will get you a properly exposed photo (not too bright, not too dark).
If you are at proper exposure and you increase one of them, you must decrease one of the other two in order to get back to proper exposure. It’s a push and pull. If you push one you have to pull one of the other two. Of course there is sometimes the option to add light but let’s just assume that isn’t an option for now.
In the graphic above, if you decreased the shutter speed to 1/100th of a second the light meter would move to the left and the image would get darker. You would then have to increase ISO or decrease (open) the aperture to get back to a proper exposure. Each setting has side effects too…some good, some bad. The exposure triangle (below), is often used to demonstrate the three exposure variables.
Aperture, Shutter Speed, and ISO each take a side of the triangle. The arrows show you which values increase exposure (brightness) while the square graphics show you what the side effects are. Let’s go through each one in a little more detail.
ISO
ISO stands for International Organization of Standardization. You’ll hear a lot of people pronounce it like a word “eye-sow” but it’s really I.S.O. The higher the ISO value, the more sensitive your sensor is to light. As you increase the ISO value you also increase the amount of noise in the image. The goal is to keep your ISO value as low as possible or at least below a level that introduces an unwanted amount of noise.
For me and my current cameras, ISO values above 400 produce an excess amount of noise. There are tools to reduce noise but I use them very sparingly and prefer to start an image that is as clean as possible. This is especially important if you’re planning to make large prints which I often do. Your noise tolerance will depend on how you are using your photos. If they’re just going on Instagram or Facebook you can get away with higher ISO than if you are making large prints.
You can also check out sensor data for a lot of cameras at Photons to Photos to see how much noise is produced at various ISO values. Some cameras have jagged noise profiles so it might be worth taking a look. One of my cameras has lower noise at ISO 200 and 400 than at 250 and 320.
There are certainly times when higher ISO values are necessary, especially in low light or when you need to push one of the other variables higher. Astrophotography, concerts, low light, and freezing motion can require high ISO values. The other two variables and/or overall amount of available light should inform the need for a higher ISO as a last resort to get the shot. If you have a fixed aperture lens like most phone cameras, you’ll find yourself adjusting ISO more often since you are limited to only two variables in stead of three.
Aperture
Aperture is the opening in the camera lens which can be adjusted to be smaller or larger. A larger aperture opening lets more light in and a smaller opening lets less light in. Most phone cameras, however, have a fixed aperture which means you can’t adjust it. If you’re in that boat then you can only adjust ISO and Shutter Speed.
If you can adjust your aperture then you’ll quickly notice the side effects of doing so. A small aperture value (e.g., 1.4) means a wide opening. A small aperture/wide opening lets in more light and results in a shallow depth of field. The lower the number, the wider the value, the more light, and the shallower the depth of field. You’ll often see aperture shown as a number with the letter F in front. Aperture is also often referred to as the F-stop.
A shallow depth of field means a shallow depth of focus. Your focus point will be in focus but things in front of or behind that focus point will quickly fade out of focus. This can be an advantage or a disadvantage depending on what you’re going for. If you’re taking a portrait, you may welcome an out-of-focus background and go for the wide aperture.
If you’re taking a landscape photo with a subject in the foreground and mountains in the background, you’ll probably everything as sharp as possible so go for a small aperture. A small aperture will also allow you to get those beautiful sun stars. This works for any bright light source including street lamps as in the image below.
In many cases, a small aperture aimed at getting a deep depth of field combined with a low ISO will push your shutter speed low enough to introduce the risk of camera shake. More on that below.
Shutter Speed
Your camera’s shutter opens to let light in and then closes to stop letting light in. The longer it is open, the more light it lets in. Really short shutter speeds (less than 1/500th of a second) can freeze motion and are useful for sporting events and freezing fast-moving subjects. Longer shutter speeds (more than 1/8 of a second) can capture motion blur and are useful for capturing movement in waterfalls, clouds, light trails, etc.
If you aren’t in a situation that calls for an especially short or long shutter speed, choose aperture and ISO first and see what your shutter speed ends up at for a proper exposure. Everyday shots of still subjects are usually taken in the range of 1/30th to 1/200th of a second. At the lower end of this range you’ll have to evaluate the risk of camera shake.
Camera shake can occur when attempting to “hand-hold” the camera with slow shutter speeds. The general rule is that your shutter speed needs to be at least 1/Focal Length of your lens. So if your lens is 85mm, your shutter speed needs to be at least 1/85 of a second to get a sharp image of a still subject. As you get below 1/40th of a second it is a good idea to use a tripod or otherwise stabilize your phone to avoid camera shake. You can get inexpensive compact tripods for your phone to get you started.
Manual Mode
To begin experimenting with these settings you’ll have to put your camera into one of the manual modes. Dedicated cameras often have multiple manual modes; I’d recommend going for full manual to get the hang of these concepts first. It is usually denoted with the letter M on the shooting mode dial or menu. I’ll get into the other manual modes in a future blog post.
Some phone cameras have a “Pro” mode that will allow you to manually adjust settings. For phones that don’t, you can install a pro camera app that will add this functionality for you. Just do a quick Google or YouTube search for best pro camera apps for your type of phone. Once you’ve gotten into manual or pro mode, the settings for ISO, shutter speed, and aperture should be pretty obvious. Remember, if your lens is fixed aperture (many phones) you’ll only have two settings to worry about, ISO and shutter speed.
That’s it! Yes there are lots of other settings, knobs, and dials but for those of you just getting started with advancing your photography, basic exposure is just three settings. Grab a tripod and go do some experimenting!
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