After looking at aesthetic choices in photography in the last chapter, we’ll now step back to fundamentals of camera technology. How do cameras work? How have they changed over time? How does the available technology shape what we see in photographs and what styles we like?
Exposure
Exposure is a key concept in the technical process of photography. While many modern cameras automatically choose the settings for proper exposure, understanding the exposure tradeoffs can help with challenges like taking photos in low light or capturing motion without any blur.
Key ideas:
- Cameras are essentially devices for capturing and recording light over time.
- Exposure has three factors: shutter speed, aperture and ISO.
Related slides for reference
✓ Human bodies react to lighting conditions in the world around us, such as the pupils of our eyes becoming smaller in bright sunlight and larger in dark places. Pupils changing size is similar to what part of photo exposure: aperture, shutter speed, or ISO?
🗨 Try this with your smartphone, which will adjust exposure automatically: Take a photo of an object, like your notebook or hand, in a bright area and then in a dark area. How does your phone react or function differently? You might note changes in how long it takes to focus, the quality of the photo, etc.
Next, try out the settings for adjusting exposure by using an online camera simulator such as the CameraSim simulator.
Take photos until you feel comfortable with how the settings work. Purposely take some poorly exposed photos, too! That’s helpful to see how different settings interact.
Using the simulator or a real camera reveals other effects of the exposure triangle:
- Aperture affects the depth of field, so using a wide aperture can make backgrounds blurry.
- Shutter speed affects motion blur, so it can be used artistically in different ways.
- Higher ISO settings that make the sensor more sensitive to light are associated with "noise" or digital fuzziness.
✓ If you want to freeze motion, such as the pinwheel spinning in the simulator, should you use a fast shutter speed or a slow shutter speed? What is one example of a specific shutter speed setting from the simulator that can freeze motion?
Making Use of Exposure
In the past, all cameras required the photographer to understand and manually adjust the exposure settings. These days, digital cameras often have very good automatic settings and achieve proper exposure without the photographer's involvement. However, serious photographers still often use manual settings because this allows for more artistic control over how photos turn out.
For example, using a wide aperture allows for a narrow depth of field, meaning only a sliver of the space in front of the lens is in focus. Conversely, intentionally using a small aperture keeps the scene crisp and in focus for a great distance. The other parts of the exposure triangle need to balance out the very wide aperture (lots of light) or very small aperture (very little light).
Example of a wide aperture, f/2.8. This is popular for small subjects and details. Only a tiny sliver of the flower is in focus. Photo by Torsten Behrens, CC BY 2.0.
Example of a smaller aperture, f/8. This is popular for landscapes and city scenes. We can see the train in focus far into the distance. Photo by Nelso Silva, CC BY-SA 2.0.
Freezing motion requires a very fast shutter speed. But sometimes it's an artistic choice to use a longer shutter speed for motion blur. Using a very long shutter speed is called long exposure photography, and it is popular for night photography when a longer shutter speed also helps to get enough light.
Example of fast shutter speed (1/3200 sec.) freezing motion. Photo by Bethan, CC BY-NC-ND 2.0.
Example of slower shutter speed (1/10 sec.) for artistic purposes. Photo by Geraint Rowland, CC BY-NC 2.0.
Example of long exposure (30 sec) with a tripod. Photo by Gary Paakkonen, CC BY-NC-ND 2.0.
🗨 Whether you’re an experienced photographer or not, what’s one specific goal you could accomplish in the next month to improve your understanding of manual exposure?