When you’re just starting out as a photographer, one of the biggest challenges can be using the correct shutter speed and aperture values. Shooting a correctly exposed photo in manual mode is an amazing feeling. But unless you know the relationship between shutter speed and aperture it may not happen very often.
In this article I’ll talk about how to use the shutter speed and aperture values efficiently to get properly exposed photos.
Note: To get full control of your camera’s shutter speed and aperture values you need to put it in Manual Mode.
What happens when you adjust the aperture value
When you increase the aperture value the aperture opening inside the lens gets smaller, reducing the amount of light that can enter the camera. Similarly, when you decrease the aperture value the opening gets bigger, allowing more more light to enter the camera.
Here’s an example to help you understand how changing the aperture value affects the shutter speed.
Let’s say you’re using a 24-70mm f/2.8 lens with a default aperture value of f/8. At a shutter speed of 1/200th of a second your camera will give you the correct exposure.
EXIF: f/8, 1/200th sec, ISO 100
Now you want a shallower depth of field (more blur effect), so you reduce the aperture value to f/2.8. Because you’ve reduced the aperture value by three stops, the aperture opening is now letting three stops more of light into the camera. The result? An overexposed image.
If you reduce the aperture value, you must increase the shutter speed by the same number of f-stops to compensate. Similarly, if you increase the aperture value, you must slow down the shutter speed by the same number of f-stops.
In this example, you’ve reduced the aperture value by three stops. So to get the correct exposure at f/2.8 you must increase the shutter speed by three stops to 1/1600th of a second.
EXIF: f/2.8, 1/1600th sec, ISO 100
Another example might be if you’re shooting a landscape. This time you want a deep depth of field, so you choose an aperture value of f/16. You’ve increased the aperture value by two stops (from f/8 to f/16), so you’re letting two stops less of light inside the camera. At a shutter speed of 1/200th sec this give you an underexposed photo.
Underexposed image at f/16, 1/200th sec, ISO 100
To get the correct exposure, you need to slow down the shutter speed by two stops to 1/50th of a second. With the aperture value two stops higher (f/16) and the shutter speed two stops lower (1/50th sec) your photo will be perfectly exposed just as it was at f/8 and 1/200th sec.
What happens when you adjust the shutter speed
When you increase the shutter speed the camera shutter opens and closes more quickly, reducing the amount of light that enters the camera. Similarly, when you reduce the shutter speed more light enters the camera.
Starting with the same base camera setting as before (f/8 at 1/200th sec), let’s see how changing the shutter speed affects the aperture value.
Let’s say you’re a wildlife photography, and you want to take photos of a flying bird. To avoid any blurring you’d need to increase to 1/800 sec. You’ve increased the shutter speed by two stops, and so you have two stops less of light entering the camera sensor. At f/8 this would give you an underexposed image.
Because you’ve increase the shutter speed by two stops to 1/800th sec, you must also reduce the aperture value by two stops to f/4 to get the same correct exposure you had at the f/8 and 1/200th of a second you started with.
Or perhaps you intentionally want to capture a panning shot, and s reduce the shutter speed to 1/50 sec to get the effect you want. Reducing the shutter speed by four stops (from 1/800 sec to 1/50 sec) means you’re letting in four stops more of light into the camera. And at f/8, that would give you an overexposed image.
To get the correct exposure you’d need to increase the aperture value by four stops to f/32.
By remembering these examples when you’re shooting in manual mode, you should end up with far more photos that are correctly exposed.
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