In Part 2 of Exposing The Triangle: The Exposure Triangle for Beginners, we went over the basics of ISO; what it is, the different elements and how they impact proper exposure. In this lesson, we are going to cover shutter speed and its impact on the overall process.
What is shutter speed?
Shutter speed refers to the amount of time the camera's shutter is open and allows light to enter the camera's sensor. A slow shutter speed will allow more light to hit the sensor compared to a fast shutter, which will allow less light. Shutter speed is measured in seconds or fractions of a second, such as 1/125, 1/250, 1/500, and so on.
Motion Blur
I should mention Motion Blur before going any further. Motion Blur is a negative side affect of using an incorrect shutter speed in relation to the motion or movement that is being photographed. Objects will show up blurry or "streaky" as a result. Typically, you would want to avoid motion blur in your photos, unless you are going for an artistic style image.
How does shutter speed impact exposure?
It is important to balance shutter speed, along with ISO and aperture, to get a proper exposure, based on the shooting conditions and image you are trying to capture. Here are some typical shooting situations in which it is important to assess how your shutter speed impacts exposure:
Sports/Action/Wildlife - In scenarios with fast movements, it is usually wise to use a fast shutter speed to freeze motion. A fast shutter speed will expose the camera's sensor to light for a very short amount of time, thus capturing an image in which motion can be described as "frozen". To properly expose for this type of image, you would need to compensate for the fast shutter speed and the lack of light hitting the sensor. By increasing aperture, the sensor is exposed to more light for that split second. Or you could increase the ISO, which would increase the sensors sensitivity to light.
Indoor or Low Light - In situations with low light, you should use a slow shutter speed to allow more light to hit the camera sensor. A slow shutter speed will expose the camera's sensor to light for a longer period of time, allowing it to capture any image where light is of concern. To compensate for a slow shutter speed and more light, the photographer would need to be mindful of the aperture and ISO values. Shooting in low light can be tricky. If light is scarce enough, a photographer might find themselves shooting at a slow shutter speed, high ISO and wide aperture to achieve proper exposure. Be mindful of your settings when operating under these circumstances. Too high of ISO can introduce nose and degrade image quality and too slow of a shutter speed can cause motion blur (see above).
Flash Photography - Without going to in-depth on flash photography, there are a few things to note when it comes to the relationship between flash and shutters speed. Every camera has a flash sync speed which is the maximum shutter speed that you can use while still being able to use flash. This is typically around 1/200th to 1/250th of a second on most cameras. If you use a faster shutter speed than the flash sync speed, the shutter curtain will block some of the flash's light resulting in an uneven exposure. High-Speed Sync (HSS) is a flash photography technique that allows you to use a faster shutter speed than the camera's flash sync speed. This is useful when you want to use flash photography in bright sunlight or to create a shallow depth of field in your photos.
Shutter Priority Mode
Most cameras have various shooting modes. These include Program Auto, Aperture Priority, Manual and Shutter Priority. In Shutter Priority mode, the Photographer has control over the shutter speed while the camera controls aperture and ISO (if Auto-ISO is enabled). The camera will do its best to get an accurate exposure based on the current shutter value. Shutter priority mode is useful in situations where capturing motion is important. Sports/Action/Wildlife photography is a good example when combating motion blur through the use of a fast shutter speed is important. On the flip side, if you wanted to show motion blur, you could set a slower shutter speed, then have the camera adjust aperture/ISO so that motion blur is present. Manual Mode also accomplishes the same thing, but the Photographer would also need to adjust Aperture and ISO to maintain proper exposure.
How to change your camera's shutter speed
How you change your shutter speed will depend on your camera. Some commons methods include:
A dial on the front or back of the camera grip.
A dial on top of the camera.
Within the camera's menu.
Auto ISO and Shutter Speed
Most camera's that have Auto-ISO have a configurable field in which you can set the minimum shutter speed. The minimum shutter speed setting allows you to specify the slowest shutter speed that the camera can use before it starts increasing the ISO. For example, if you set the minimum shutter speed to 1/125th of a second, and the camera's light meter determines that the current exposure requires a shutter speed slower than 1/125th of a second, the camera will increase the ISO instead of slowing down the shutter speed. This can help to prevent motion blur and ensure sharp images, particularly when shooting handheld or in low light. It is important to note that using Auto ISO and minimum shutter speed settings can result in increased image noise, particularly at higher ISO levels. Therefore, it is important to balance the minimum shutter speed with other exposure settings, such as aperture and ISO, to achieve the desired balance between exposure and image quality.
Conclusion
Shutter speed is an essential component of the exposure triangle, and it plays a crucial role in determining the amount of light that hits the camera's sensor. Understanding how to balance shutter speed, along with aperture and ISO, is critical for achieving proper exposure and capturing high-quality images in various shooting situations. By adjusting the shutter speed, photographers can freeze or blur motion, capture low-light scenes, and even use flash photography techniques. With practice and experimentation, photographers can master the art of shutter speed and use it to create stunning visual compositions.
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