A gentle introduction to camera exposure Aperture, Shutter Speed and ISO
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TL;DR // If you want more control over your photography, you'll want to understand the 3 main variables with your camera that affect exposure: Aperture, Shutter speed, and ISO.
You're learning how to use a camera and it's time to move beyond using AUTO (automatic) mode. Let's look at the 3 things you want to understand.
The 3 variables you should care about
- Aperture
- Shutter speed
- ISO
Each of these affect how much light hits the sensor (or film). But they also affect other important aspects about the final image.
Demo time
Click the blue arrow buttons below to change the Aperture, Shutter and ISO settings. The image will automatically update to simulate the result.
More light
Aperture affects focus
Less light
More light
ISO affects grain
Less light
Disclaimer: No this isn't an accurate representation of an exposure calculation. It's a little toy to help you learn how each variable affects the final image!
Explanations
Aperture, shutter speed and ISO all affect the brightness, but there are specific reasons to adjust one or the other.
| Setting | Affects | How it affects your photo |
|---|---|---|
Aperture |
Depth-of-field | How much of the space in front of and behind your subject will be in focus? A small aperture (e.g., f 2) will mostly only have your subject in focus. With a larger aperture (e.g., f 8), your subject and much of the foreground and background will be in focus. (Note that zooming into a subject also has the effect of shortening your depth-of-field.) |
Shutter speed |
Motion blur | This is how long the shutter is open to take the photo. If the subject (or the camera) moves while the shutter is open, it may be blurry. To avoid blur on still subjects, you'll want 1/60s at the lowest. If you zoom in or photograph sports, you'll need even faster shutter speeds (e.g., 1/1000s or faster). |
ISO |
Grain | For both film and digital cameras, the higher the ISO, the more 'grain' you will see in the final image. With more recent digital camera sensors, the effect is not nearly as pronounced as it was just 10 years ago. |
How do I use this to improve my photos?
When I'm taking photos, I tend to switch between two camera modes:
- Aperture-priority Av
- Shutter-priority Tv
Aperture-priority
You pick the aperture, and the camera picks the shutter-speed automatically for the exposure. This is what I use 90% of the time.
Why? Because I'm usually interested in depth-of-field and I tend to shoot static landscape and architectural scenes (without moving objects). I also tend to shoot with a tripod so I can have small apertures (for large depth-of-field) and not worry about motion blur.
When I photographing people -- primarily portraits -- I want the opposite. I'll switch to a wide open aperture (e.g., f 2 or f 1.8 to get a face in focus, and everything else blurred.
Shutter-priority
In Shutter-priority, it's the opposite. You pick the shutter speed, and the camera adjusts the aperture automatically.
If you're shooting fast moving subjects and need to keep things in focus, this is probably appropriate. I rarely use this, but only because the things I photograph tend to be static.
Conclusion
This has been a very basic introduction to the concepts of the 3 camera variables in photography: aperture, shutter speed, and ISO.
If you really want to learn about exposure settings, I recommend the following online resources:
- Exposure Basics (Digital Camera Know-Hows)
- Good reference website with lots of details about cameras, optics, photography
- Video: Exposing Digital Photography - Exposure
- YouTube series of Harvard digital photography courses
// ka
