Getting a correct
exposure happens by balancing three important parts of the exposure triangle:
1.
aperture
2. shutter speed
3. ISO
Today we're going to talk about what your
shutter speed does and how it affects your photos.
Your shutter speed refers to
the amount of time your camera's shutter is open when you're taking a picture. Shutter speed is measured in seconds (in most cases fractions of a second.) When you see a shutter speed of 1/250, that means the camera's shutter was open for 1/250 of a second.
Shutter speed affects two things:
#1 The length of time your sensor is exposed to light.
#2 How your camera captures motion.
#1 Unpacked: (Shutter speed affects exposure - how bright/dark your image is.)
The longer your shutter is open, the more light there is to land on the sensor resulting in a brighter exposure. The opposite is also true. The shorter the length of time your shutter is open = less light on the sensor = a darker exposure.
Example:
So if I've just taken a picture with a shutter speed of 1/250 seconds and it came out underexposed (too dark), one way that I could brighten the next picture I take is to change the shutter speed to keep it open longer. Keeping the shutter open longer allows more light to fall onto the sensor giving you a brighter image. Changing the shutter speed from 1/250 seconds to 1/125 seconds would give you a brighter image because the shutter is open for a longer period of time letting in more light.
My Eye Analogy:
It helps me to think of shutter speed like a blinking
eyelid. Start with your eyes closed. Now open your eyes very quickly and immediately close them again as fast as you can. That's like a
fast shutter speed. You didn't let a lot of light into your eyes because your eyelid (shutter) closed so quickly.
Now close your eyes again. This time open your eyelids and leave them open for a while before closing them. That's like a
slow shutter speed. You let a lot of light into your eyes (sensor) because your eyelids were slower to close.
#2 Unpacked (Shutter speed also affects the way motion is captured.)
A fast shutter speed freezes
motion while a slow shutter speed will show motion blur. One of the reasons why we may get undesirable blurry pictures of our kids is because the shutter speed may not be fast enough to freeze their motion.
My Eye Analogy:
Think about the eye analogy above. Start with your eyes closed again. Now take your pointer finger and move it back and forth in front of your eyes. Simulate a
fast shutter speed by quickly opening and immediately closing your eyes. You weren't able to see much of your finger's motion because your eyelids (shutter) closed so quickly.
Now close your eyes and move your finger back and forth in front of your eyes again. This time simulate a
slow shutter speed by opening your eyelids and leaving them open for a while before closing them. You were able to see a lot of your finger's motion because your eyelids were open for a longer time.
When your camera captures that motion and puts it onto a 2 dimensional photograph, the result is blur.
Examples:
For most portraits and pictures of people, blur is bad. We want nice, sharp, crisp images and one contributing factor is to use a shutter speed that is fast enough for the situation.
Jumping shots require a
fast shutter speed to freeze motion:
XSI, 50mm, 1/250, f/3.2, ISO 200
So do swinging shots:
D7000, 50mm, 1/500, f/1.8, ISO 1600
However, there are certain situations where motion blur can add an artistic element to a photo. You want to use a
slow shutter speed to capture motion in the following situations: to photograph wispy waterfalls, a fast moving train/car that appears to be in motion, the red and white trails of traffic.
I don't like this next picture because it is poorly exposed and has camera shake, but it gets the point across about motion blur and a slow shutter speed. This is our train set around our Christmas tree this year. I should've put the camera on a tripod (don't have one) or at least a stable surface.
35mm, 1/25, f/1.8, ISO 2000
Some general guidelines:
1. Don't drop your shutter speed below 1 over twice the focal length of your lens. So if you're using a 50mm lens, don't go below 1/100. If you're using an 85mm lens, don't go below 1/170.
2. If you're shooting toddlers or moving children, keep your shutter speed above 1/250.
3. For swing shots, jumping shots, or sports, try to keep it above 1/500 to freeze motion if you have enough light.
I hope that makes a little sense! I know all of this can be confusing at first and it really takes a lot of practice! I'll be talking about the 3rd and final piece to the exposure triangle next time: ISO.
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