Photography is difficult enough, right? With all of the rules, the gear and the mathematics (what now?), it can get a little too much to get your head around. That’s why we like to simplify things.
One of the areas we can better understand is the exposure triangle. This consists of the ISO, aperture and shutter speed. Bookmark this article and use it as often as you need to.
Exposure Triangle
The exposure triangle helps us understand more about light. In photography, it is all mathematical behind the scenes. It is the same for film photography and digital photography alike.
Haven’t you ever wondered why the numbers seem strange, and increment in an even stranger way?
Apertures rise from f/1.4 to f/2.8 and go all the way to f/22. Shutter speeds could be 1/125, or 1/250 and all the way to 1/4000 (if you’re lucky).
Same goes for the ISO where it jumps from 100 to 200 and keeps going to 3200.
The exposure triangle shows you the three main components of image capturing: ISO, Shutter Speed, and Aperture. All three use light to allow images to be taken.
The ISO looks at the sensitivity of the scene, the shutter speed allows for freezing for motion blurring the subject and the aperture directly commands the depth of field. You need all three, but this triangle shows us that if light conditions change, you can change your settings to match.
Understanding the exposure triangle is the fundamental and most important aspect of photography. Your film camera or digital sensor will tell you how much light is entering your camera via the exposure value scale.
ISO
ISO is your camera’s sensitivity to light, with a typical range of 100-1600. Some cameras can go as low as 50 or 64, and reach as high as 12,600, but these are found in very expensive camera bodies.
Basically, the lower the ISO number, the less light is hitting your sensor. The amount of light in your scene is important, and your camera sensor will tell you how much is enough.
More light is needed at the lower ranges to get a good exposure, meaning more light for the higher ranges. The lower the number, the better the resolution and quality of your resulting images.
Higher ISO numbers allow you to photograph in low light conditions, yet these settings bring more grain.
DSLRs and even other digital cameras, like mirrorless systems can cope well with high ISO numbers. Their sensors, processors and large pixel sizes are able to cope with the digital noise. However, as a rule, use an ISO with a value as low as possible.
For shooting in a sunny day, ISO’s 100-200 are perfect. If you head indoors, you may find that you will need to use ISO’s 800-1600.
ISO settings are best used in manual mode, but it can be placed on Automatic on Canon cameras.
Aperture
The aperture is the hole inside your lens, which acts as the ‘iris’ similar to your eyes. A wide or low-number aperture, such as f.2/8 will have a very small focal length.
This means that wherever you place your focus, only a small part of the subject will appear clear.
A narrow aperture, such as f/16 will place the entire scene in focus, as it has a large focal area. Landscape photographers are more likely to use a narrow aperture if they want to show the foreground and background as clear and sharp.
The lower the f-stop, the more light is allowed to enter your lens, and therefore, hitting your camera sensor.
To keep my ISO value down, to retain quality, I shoot live musicians with a wide aperture. This gives me more usable light.
A high f-stop number gives me less light to play with, which tends to mean that longer exposures are needed. To create images with a bokeh background, you would use a wide aperture.
There are some complicated matters surrounding the aperture. You can talk about the hole in your lens in two ways, either using ‘aperture’ or ‘f-number’. The complication comes when we talk about their comparatives and superlatives.
A high f-number is the same as a narrow aperture, such as f/22. A low f-number is the same as a wide aperture, such as f1.2. The f-number is looking at the specific number used, where as the aperture relates to the speed and depth of field you get with that number.
Aperture priority mode is a camera setting mode you can use. It forces your camera to think of the aperture and ISO before the shutter speed. In this mode, the shutter speed will bounce around depending on your scene, but the aperture will stay the same.
Shutter Speed
Your shutter speed can be thought of as the amount of time your camera’s shutter stays open. The longer it stays open, the more light enters your scene and therefore your image.
These numbers are shown in fractions of a second, where 1/250 of a second is a typical value.
Your shutter speed has an effect on the sharpness of your subject. A lower or slower shutter speed lets in more light, but also allow more blur from your subjects, especially if moving.
A faster shutter speed lets in less light, but gives you a sharper image as the subject is ‘frozen’.
Without a tripod, I wouldn’t recommend a setting below 1/100th of a second, unless you are taking advantage of a creative motion blur.
A shutter speed chart is another great way to remember what shutter speeds are best for each situation.
Shutter priority mode is another camera setting mode you can use. It forces your camera to think of the shutter and then ISO before the aperture. In this mode, the aperture will raise and lower depending on your scene, but the shutter mode will stay the same.
Combining the Settings
Well, the numbers do have a pattern and they are chosen so. Look at aperture for example, and see if you can spot it. A typical range would be f/1.4, f/2.8, f/4, f/5.6, f/8, f/16 and f/22. The numbers almost double every time.
For the ones that don’t (f/4 and f/22), they are usually the previous two numbers added together (or thereabouts).
The same goes for ISO, where the numbers double each time. 100 goes to 200, then 400, 800, 1600 and finally 3200. Shutter speed follows suit with 1/125, 1/250, 1/500, 1/1000.
Each of these numbers is one stop. They either add or subtract one stop’s worth of light from your image. The reason we show them in a triangle is that they all work together.
For example, you have a correct lighting scene at ISO 100, shutter speed at 1/125 and an aperture of f/16. But what happens when the sun disappears behind a cloud?
The scene just got two stops darker. This means you need to add two more stops of light into your settings for a correct exposure.
You could add it using ISO, changing it from 100 to 400 (100 -> 200 -> 400). Here, you compromise the resolution and quality of your image. A higher ISO brings grain and digital noise.
Your shutter speed could change two stops from 1/125 to 1/30 (1/125 -> 1/60 -> 1/30). In doing this, you will have a high level of camera shake in your image. we can’t change them without compromising the image.
In this case, we would change the aperture from f/16 to f/8 (f/16 -> f/11 -> f/8).
Looking for more tips? Check out our new post about fast shutter speed next!
And make sure to check out this cool video on the exposure triangle before you go!
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