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Exposure Triangle: ISO, Aperture & Shutter Speed

By: Jenee Cook Photography

Having complete control over your images begins with your camera settings. Get out of Auto-mode and into Manual!

Why is my photo so dark? How do I blur the background behind my subject? Why isn't my photo sharp?

 

While the camera is in auto-mode, it chooses for you what it thinks you are trying to expose for. Being able to have control over your camera settings and being able to tell it what you want it to do instead of letting it think for you, will make is so you have complete control over your images. To be able to control all aspects of your camera, first switch it from Auto to Manual mode. You can only change these settings while in Manual mode. The three main camera settings that you'll have control over are: ISO, Aperture, and Shutter Speed. Let's look and see what each of them control independently...

In the graph above you will see represented Exposure settings displayed in a triangle: ISO, Aperture, and Shutter Speed . This is how I presented it in my live-video below as well and broke each angle apart and explained them. I've also created the exposure settings broken apart in a graph and have made it available as a free download.  

 
  • ISO is the sensors sensitivity to light. Choosing a higher ISO number makes the sensor more sensitive to light. The lower the ISO number, the less sensitive the sensor is to the light. 

Increasing the ISO will make the photo brighter or more exposed. Increasing the ISO will also introduce noise into the photo however. The higher the number, the more noise. But don't shy away from bumping up that ISO to get the photo! It is better to get the image with noise in it than to miss the moment forever. When deciding what to set the ISO at, determine what is the lowest ISO setting possible for the situation. While shooting with strobes or studio lights, you will have your ISO set at about 100. When using natural light, you will need to use whatever ISO you need to make the image bright enough to use the chosen shutter speed and aperture for the image you are wanting to create. 

 

  • Shutter Speed refers to the length of time the shutter is open. The faster the shutter speed the less time the shutter will remain open. The faster the shutter the better it is at freezing any motion. However, because the shutter isn't open as long, less light is going to be getting to the sensor so the image will be darker. If the objective of your photo is to freeze motion while using a fast shutter speed, you can brighten the exposure by increasing the ISO or by opening up the aperture if needed.

          Increasing the shutter speed will help to eliminate blurry photos as well. 

 

 

 

 

  • Aperture: is a hole located in the lens that when it opens and closes it controls #1) depth of field and #2) how much light is let onto the sensor. 

Depth of Field refers to the the space in front of and behind the subject that is in focus.

  • A lower number Aperture will have a narrower depth of field. This will give you that "blurry" look behind the subject known as bokeh.  

Warning- having a very narrow depth of field can lead to soft focus issues if you aren't aware of focal distance (another in-depth topic for another time). 

  • A higher number aperture will have a greater depth of field. More of the image will be in focus from front to back. A higher number aperture is often used in landscape photography to have the whole area in focus, from the stream right in front of you the mountains in the distant. 

 

The numbers for aperture are also termed as an "f-stop." The aperture is represented by the letter F and a number. There is some math involved in assigning which aperture opening gets its number. But we won't go into that. You just need to know a low-number aperture number would be stated as f/1.4. A high number aperture would be stated as f/16.

I like to think of an aperture in a lens as being like the pupil in a cats eye. The darker it is, the bigger the cat's pupil gets. It lets in more light. The brighter it is, the smaller the cats pupil gets. The less light is allowed in. Now this is the tricky part.

The more the aperture opens; or the bigger the opening is, the smaller the f-stop number. So a very wide open aperture would for example be f/1.4

The more the aperture closes; or the smaller the opening is, the larger the f-stop number for example f/16

Putting the three all together to properly expose a photo

 

Now that we know what each setting does independently, how do we know if our photo is too dark or too bright? The camera's built-in meter sensor can be seen while looking through the viewfinder. This meter will indicate if the photo is under exposed, over exposed or correctly exposed. When the indicators are over to the + side, the image will be too bright. When the indicators are on the - side, the image will be too dark. A properly exposed image will have the indicators at the 0 or the middle of the meter. This is also known as nulling or zeroing out the meter. 

Now you can independently move each setting to practice what happens to the meter, keeping in mind what we went over above and how to make the image brighter or darker. 

  You will need to decide what the purpose of your photo is. Is it you need to get a whole group of people in focus? Your f/stop will need to be a big aperture number to have a bigger depth of field to keep everyone in focus. So that's the important setting set it to say f/8. Now, you can also increase or decrease the shutter speed to let in more light or less light. You don't want to drop the shutter speed too slow or you will get blurry photos. If after adjusting both the f/stop and shutter speed and your image is still too dark, adjust your ISO to let more light in. Watch the built-in meter so watch watch your exposure is doing. 

 

  • Determine what the important camera setting is. Lock that one in and adjust the other two settings so the photo is correctly exposed. 

 

There ya go, now go and do your homework! After changing your DSLR into Manual mode experiment with each camera setting: ISO, Shutter Speed and Aperture. Pay attention to how changing each setting changes the exposure and overall image. Watch the build-in meter to help you in experimenting. Right now you aren't looking to create a beautiful photo, you are just seeing what each setting does. 

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