The Exposure Triangle refers to the three main camera settings: Aperture, ISO, and Shutter Speed. You must become intimately familiar with these 3 concepts in order to improve your photography.
Look again at the Exposure Triangle. You'll notice that Aperture and Shutter Speed are at the bottom, with ISO overhead. I've arranged the 3 settings this way on purpose. Aperture and Shutter Speed both control the amount of light physically entering the camera. Once the camera has taken the photo and captured the light, the ISO amplifies (brightens) that light. This is crucial to understand. The only ways to capture more light are a longer Shutter Speed or wider Aperture. Increasing the ISO does not actually capture more light, it only brightens whatever light was captured.
When the Camera is set to Auto mode, it automatically chooses the Aperture, ISO, and Shutter Speed to get a properly exposed photograph. Therefore, it may not give you the optimal settings you need. For example, if you are shooting a soccer game, the camera may not use a fast enough Shutter Speed and all your photos will be blurry.
As you get more comfortable with your camera, you should start using different shooting modes like: Shutter Priority Mode, Aperture Priority Mode, and Manual Mode. In Shutter Priority you can choose any Shutter Speed you want, the camera will choose the appropriate Aperture and ISO. This is great for Sports and Wildlife photography! In Aperture Priority mode you can choose the Aperture you want and the camera will choose the appropriate Shutter Speed and ISO. I use this mode for Portraits and Landscapes. On Manual Mode you can use whatever settings you want, the camera won't help you out (unless Auto ISO is enabled.)
Keep in mind, all 3 settings are dependent on each other. If you increase your Shutter Speed, you will have to change your ISO or Aperture to compensate for the loss of light.
Aperture literally means "hole, or opening." In photography, the Aperture refers to the opening in our lens. Changing the Aperture value changes the size of the lens' hole. When it is wide open (f/2.8), lots of light can come through. When using a very small aperture (f/22), only a little light will pass through the lens. The image below shows the aperture in my lens. In this case, it is showing an example of f/22.
A narrow aperture
Below are the main, 1 Stop, Aperture increments. Each Stop either doubles the amount of light entering the lens, or cuts in in half. As you travel up the chart below, from left to right, you are losing one Stop of light each time. In this case f/1.4 is a large opening and f/22 is a tiny pinhole.
So if you "Open Up" the Aperture, from f/8 to f/5.6 you have just doubled the amount of light entering the lens.
If you "Stop Down" from f/2.8 to f/4 you have cut the amount of light in half.
Pull out your camera, set it to Aperture Priority Mode (A or AV on your top dial) and follow along for the remainder of this Aperture Section. When in A (or AV on Canon) mode, you can use your camera's main scroll wheel to change your Aperture. If you are still unfamiliar with the scroll wheels and buttons on your camera, refer to your camera's manual. It will explain everything clearly (you should also be able to find a PDF online, if you lost it) You should see the Aperture value getting larger or smaller as you scroll the wheel.
Every lens is different. If you have a kit lens that came with the camera, it may only open-up to f/5.6 for example. An expensive portrait lens may be able to open-up all the way to f/1.4. If you plan to shoot in low-light scenarios, consider upgrading to a lens that can at least open to f/2.8, if not f/1.8 or f/1.4.
There are Aperture values in-between the numbers above. These are 1/3 Stop increments, you should have two Aperture Values to pick between each Full Stop increment.
You will see f/6.3 and f/7.1 between the Full Stop Increments of f/5.6 - f/.8. These are considered 1/3 stops. Feel free to use them as well. I highly recommend you memorize the Full Stop increments in the chart above though. This will help you out a lot!
Aperture also controls the Depth of Field.
As you move up the chart, from left to right, you gain more Depth of Field. So f/1.4 has a very narrow Depth of Field, f/22 has a very wide Depth of Field. Therefore, you would use f/1.4 to blur your scene and f/22 to get everything in focus.
The camera has a focal plane that is always parallel to the sensor. As you increase the Depth of Field, more of the scene will be in-focus. The image below shows a very narrow focal plane, caused by a wide open Aperture (f/2.8). As the Aperture value gets larger (f/8), that strip of "focus" will become larger. This is crucial to understanding Aperture and how to use it properly.
Notice the thin band of focus, Depth of Field
We want a narrow Depth of Field when doing portraits. This blurs the background, while leaving our subject sharp. Imagine that thin line of "focus" directly over the subject's face. This allows the face to be sharp, but everything behind it to be blurry. In the image below, I used an Aperture of f/1.4 for a narrow depth of field. If you have a zoom lens, like a 16-300mm / 18-200mm / or 24-120mm be sure to zoom in for nice background blur. The more zoomed in you are, the less Depth of Field you'll have.
f/1.4 blurs the background
When shooting landscapes, you generally want everything in focus. Therefore, I recommend using f/8 - f/16. This will give you much more Depth of Field. In my experience, f/8 is great for Landscapes, especially when using a Wide Angle lens. Also, using wide angle lenses gives you more depth of field than telephoto lenses. So if you want your foreground and background sharp, consider using a wider angle lens. (24mm or wider)
Use f/8 for a wide Depth of Field
When using really wide angle lenses, Depth of Field works a little different. Even at f/4 or f/2.8, you will have lots of DOF. When I photograph landscapes at night, using my 14mm lens, I can shoot at f/2.8 and get a similar Depth of Field as a normal lens at f/8. This allows me to capture a lot of light and still have everything in focus!
f/2.8 at 14mm, everything in focus
If you want lens flare in your image, you must use f/11 - f/22. Watch out though! Any dust on your camera sensor will be visible in the photo. When you shoot above f/8, the sensor dust starts to become apparent in your images. It will be especially noticeable in blue skies or other plain areas. You will need to use some Post-Processing techniques to remove this dust from your photos. If you notice a lot of dust in your image, consider getting the sensor cleaned by a professional. Click here and scroll down to the bottom for more information on sensor dust. Otherwise, avoid shooting above f/8. Shooting above f/8 will also cause Diffraction. Diffraction will cause your images to lose sharpness. For more information on Diffraction, check out this tutorial from Cambridge in Colour.
Use f/11 - f/22 for Lens Flare
So, let's recap Depth of Field. The wider the lens (14-24mm), the more Depth of Field you will have by default. The more zoomed in you are, the less Depth of Field you have (85mm - 600mm+). A narrow Aperture (f/11-f/22) increases the Depth of Field, while a wide Aperture (f/1.4 - f/4) has a very thin Depth of Field. Think back to the fly photo. The Depth of Field plane is always parallel to your camera. As you change the Aperture, the width of that plane changes. If you need more of the scene in-focus, increase the Aperture value (f/16). If you want a blurry background, use a wider Aperture (f/2.8).
By using a wide open Aperture (f/1.4 - f/4) you can capture beautiful Bokeh in your images. Bokeh is Japanese for "blur". If there are lights in the background, they will blur out nicely. Depending on which lens you use, the Bokeh qualities will change. In the image below you will see that the out of focus lights are not perfect circles. If you are looking into buying a portrait lens, be sure to research how the Bokeh looks for that lens.
It is often said that "ISO controls the camera's sensitivity to light." This is not true, technically. In reality, the ISO simply brightens the photo after it's captured. So at the camera's base ISO, 100, the image is not brightened at all. If you shoot at ISO 1600, the camera will brighten that image significantly. I use higher ISO's when I shoot in low light or when I need to have a fast shutter speed.
Below are the main, 1 Stop, ISO increments. Each Stop either "doubles the sensitivity of the sensor", or cuts it in half. As you travel up the chart below, from left to right, you are gaining one Stop of light each time.
Just like with Aperture, there are two 1/3 stop increments between each Full Stop listed above. You will see these as you manually change your ISO value. For example, there's ISO 1000 and 1250 between the Full Stop increments of 800 and 1600. It's best to just use the Full Stops however.
Click here to see a comparison of ISO 100 - 6400 on a night sky. These images were all taken with the same Aperture and Shutter Speed. Only the ISO changed. As you can see, the image became progressively brighter as the ISO increased.
ISO 100 is usually the camera's base ISO. Using ISO 100 will provide the highest quality photos, with the least amount of noise/grain. This is a good ISO to use for Landscapes on a bright, sunny day for example.
ISO 6400 is normally the camera's maximum usable ISO. You will see values above 12800 on many current DSLR's. You should avoid using these as the image quality will be terrible. Image quality will be degraded, colors will be washed out, dynamic range is reduced, and there will be heavy grain in the image. You may need to use ISO 1600 - 6400 when shooting indoors without using the Flash. Although your eyes may not notice it, it is actually quite dark inside most houses, even with the lights on. I use ISO 6400 when photographing the Milky Way, since the night sky does not give off much light.
Here's how I actually utilize ISO on my camera. Let's say I'm photographing a bird. I have the camera in Manual Mode. My Shutter Speed is 1/60 sec, Aperture is f/5.6, and my ISO is at 100. My image is properly exposed. However, the photos keep coming out blurry. I need a faster Shutter Speed. I increase my Shutter Speed to 1/500 sec. Now my image is sharp, but very dark. I can't open up my Aperture, because my lens is already wide-open. Therefore, I have to increase my ISO to make the image brighter. I change the ISO to 800. Now my image is sharp and properly exposed! If you are on Aperture Priority or Shutter Priority Mode, increasing the ISO will automatically increase the Shutter Speed.
I use ISO 6400 when photographing the Milky Way. This allows the sensor to pick up all the faint starlight. However, the images are quite noisy. If you want to learn more about Milky Way Photography, check out my Astrophotography Tutorial
Use ISO 6400 for Milky Way photos
Each camera will have it's own ISO limits. Cheaper and older cameras have worse ISO performance than newer, higher-end cameras. If you have an entry-level camera, you may not get great images above ISO 800. If you have a top-of-the-line camera you can potentially shoot at ISO 12,800 and have a usable image!
Remember, try to use a low ISO for good image quality, but increase it as necessary for faster Shutter Speeds.
Finally, read this blog post on ISO-Invariance. It should help clear up any confusion on ISO.
The Shutter Speed is simply how fast the camera's shutter closes. Watch this video to see exactly what happens inside the camera when a photo is taken. A fast shutter speed (1/1000 sec) will freeze motion, while a slow shutter speed (1 sec) will show motion blur. If you are shooting children, wildlife, sports, or cars you will want a fast shutter speed (1/500 sec+). If you are shooting Waterfalls you would likely want a shutter speed of 1 second or longer to blur the water.
Panther Creek Falls1/4 second Shutter Speed
Shutter Speed has many more Stops than ISO and Aperture. You can select anywhere from 1/8000 sec to 30 secs in the normal camera settings. It is even possible to have a shutter speed of a few hours!! Therefore, I will only list a small portion of the Full Stop increments for Shutter Speed. As you travel up the chart below, from left to right, you are gaining one Stop of light each time.
So a Shutter Speed of 1/2000 gets twice as much light as 1/4000.
Here are some general guidelines for choosing the appropriate Shutter Speed:
1/2000 - Birds in Flight / Hummingbirds
1/1000 - Sports, race cars, planes, large birds
1/500 - Kids
1/250 - Slow moving people or animals
1 second - Waterfalls
You can also add Neutral Density filters to the front of your lens to slow down your Shutter Speed. This will allow you to shoot up to 8 minute photos during broad daylight! To learn more about filters, check out my Long Exposure Tutorial.
This little trick will help you get sharp photos with any lens. First, determine your lens' focal length. If you have a zoom lens, it should say something like 70-300mm or 24-120mm on the lens. If you have a prime lens, you should see a 35mm or 50mm for example.
The Reciprocal Rule basically says: keep the Shutter Speed at least equal to the Focal Length you are shooting at. For example, if you are at 70mm, you would need a Shutter Speed of at least 1/70s.
35mm = 1/35s
85mm = 1/85s
600mm = 1/600s
As you can see, the more zoom you have, the faster your Shutter Speed needs to be. These are just general guidelines though. If you are using a tripod the camera shouldn't be moving, so you wouldn't need to bother with this. I happen to be pretty shaky when I shoot, so I usually need to shoot a bit faster than these guidelines. If you have real steady hands though, or can brace against something while shooting, you can potentially use much slower Shutter Speeds.
The Reciprocal Rule is just a useful tidbit to keep in mind, and is by no means very accurate.
I recommend downloading my Stop Guide chart. This chart has all the ISO, Aperture, and Shutter Speed increments in one photo. I would download this onto your smartphone. You can refer to it when necessary.
Aperture controls the Depth of Field. Use a Wide Open Aperture (f/1.4 - f/2.8) for low-light scenarios or to blur the background when photographing people or animals. Use f/8 when photographing Landscapes, or when you want most/all of the image in-focus. Use f/11 - f/16 to get Lens Flare in your images, but watch out for sensor dust! Use Aperture Priority Mode to easily control your Aperture, the camera will figure out the rest.
ISO controls the sensor's amplification of light. If I increase the ISO from 100 to 200, I can double my Shutter Speed from 1/250s to 1/500s. However, that means the amount of actual light hitting the sensor is halved. (Remember Stops) Therefore, the image will become more grainy because less light is reaching the sensor and the camera must amplify that weaker signal. That's the trick with ISO. As you increase the ISO, (on the Auto modes), the camera will let in less light - either by using a faster Shutter Speed or smaller Aperture. When there is less light, grain will be more apparent. When shooting at very high ISOs, the camera is barely getting any real light and has to amplify that weak signal. This causes the grain.
If you need a faster shutter speed, increase the ISO as needed. For example, moving up from ISO 100 to ISO 400 (2 Stops) allows you to increase the Shutter Speed by 2 full stops (1/250 sec to 1/1000 sec).
Shutter Speed either freezes or shows movement in photos. Use a Fast Shutter Speed (1/250, 1/500, 1/1000+) when photographing children, wildlife, or sports to freeze the movement. Use a slow shutter speed when photographing waterfalls, you will want a tripod when shooting slower than 1/30 Shutter Speed. Use Shutter Priority Mode to control your Shutter Speed, the camera will figure out the rest.
Set your camera to Manual Mode! This will allow you to select the Aperture, ISO, and Shutter Speed independently. You will be able to clearly see the effect each setting has on your image as you experiment.