Welcome back everyone! I hope everyone had an awesome Valentine’s day and I’m glad you took a little time out of your day to read the ramblings from this photo geek.
We will be continuing the 101 series with another important feature of any camera, the shutter speed.
What is it?
The camera’s shutter is the door that stands between the sensor/film and the light. When you press the shutter release button the shutter moves out of the way allowing the light to expose the sensor/film for a set amount of time.
Shutter speed is the measurement of time that the shutter remains open, exposing the sensor/film to the light stream entering the camera body through the camera’s lens. Easy stuff.
There are many different types of shutters out there, but the shutter that you will find in most DSLR/SLR cameras is a type known as a focal plane shutter (shown above). As this is the type that I deal with the most (except for the shutter in an iPhone) this is the type that this 101 will be written about.
Much like aperture F stops, the speed of the camera’s shutter is measured in stops. However, unlike the aperture, the shutter stops are measured in increments of time. These increments can be long, or incredibly short. Long increments allow more light to hit the sensor/film, while short increments only expose the sensor/film to the light for a brief moment.
Above is a diagram of shutter whole stops. Like I mentioned before the stops are measured in time, the longer the time the more light and the shorter the time the less light. As you can see fast shutter speeds are measured in fractions of a second, which makes them incredible fast. The Nikon D300s can take a picture at 1/8000 of a sec. Take a second and divide it up into 8000 sections. Just one of those sections is the amount of time the shutter is letting in light to the sensor. Amazingly fast. On the opposite end the shutter can be open for extended periods of time allowing more light to reach the sensor. Many cameras are even capable of leaving the shutter open for minutes, or even hours at a time.
How does the shutter manage to open and close at such break neck speeds? The answer is really simple and involves two elements known as curtains. Every time you push the button the first curtain (or-front curtain) moves out of the way exposing the sensor. When the set time has been reached the second, or rear curtain slides into place blocking the incoming light.
The delay between the fall of the first curtain and the fall of the second determines how long the exposure will be. A slow shutter speed means that the fall between the two will be delayed allowing more light in. A fast shutter speed means that the rear curtain will begin to fall before the front has even reached the bottom. An extremely fast shutter speed means that the front falls and the rear falls almost immediately after. This fast fall speed can cause a problem when using a flash if you are not careful (more on that later).
Shutter speed, time, & motion
Every major setting in the camera produces a visual bi-product. With aperture it is depth of field. With shutter speed it is time. By changing the shutter speed you affect the way the camera records time.
In the photo above the same pinwheel was shot at different shutter speeds and each records time in different ways. The first is at a stand still. The second shows a little motion, this motion shows a subtle passage of time in a photo. The last shot shows an even greater passage of time as we wee the pinwheel in full spin.
fast shutter speed
In this photo we see a shot freezing the passage of time. The water flowing off the swimmer is locked in mid air. This is accomplished by using a high shutter speed, which opens and closes so fast that the light it records is only from the water when it was in that spot in the air.
slow shutter speed
In this image slow shutter speed shows the passage of time indicated by the automobile lights streaking by in the background. This image was shot using a slow shutter speed and a tripod to steady the camera.
The above animation demonstrates how different shutter speeds affect the passage of time in the same image.
Motion blur & camera shake
How many times have you been taking a shot and noticed that your image was coming out blurry, but you were so sure you were focused correctly? It happens to us all the time. In most cases the blurry photo is the result of motion blur, or camera shake.
In the above image the cars are blurry because the cars are moving faster then the ability of the shutter to freeze them in place. The shutter is simply too slow. In some cases there may not be enough light for you to increase shutter speed. So, how do you get the image nice and sharp? The answer is a technique known as panning.
Panning is the technique of following the your subject with your camera at the relative speed of their motion. By panning you are briefly matching their speed, which enables you to snap a shot with them in focus. The added bonus of panning is that you still keep the motion of the photo, but now the motion is applied to the background, because you were moving your camera, but the background remained still.
Another culprit for blurry photos is camera shake. Unlike the majority of motion blur, which is due to the movement of your subject. Camera shake occurs when the photographer is at a slow shutter speed and is off balance, or has shaky hands.
This is a common problem and is easily fixed. You can use a tripod or mono pod. If neither is around you can always make a simple device to help you steady those shaky hands. Here is a link to a great video all about makeshift ways to balance your camera.
If you are using an external flash, also known as a speedlight, or shoe mount flash, you will need to know about another shutter speed law, Sync Speed
The nature of the light coming out of a speedlight is much different then that of constant light sources. Light from a flash comes in a single burst, unlike constant light, which streams from the source… constantly. If you’re shooting with a very high shutter speed and using an external flash you will run into the problem of your being very dark, or black, at the bottom.
This is due to the rear shutter curtain falling, or closing, before all the light is finished exiting the flash unit. To solve this it is necessary to set your shutter speed no higher then the sync speed. The sync speed is the fastest shutter speed allowed with out the problem mentioned above, usually 1/250 of a sec.
Modern radio triggers also have clever ways of avoiding this problem. Rather then releasing the flash in one burst, the radio trigger forces the flash to fire in consecutive bursts, like a strobe light. This allows shutter speeds well above 1/1000 of a sec.
I hope this posts helps those of you who may have been a little confused by shutter speed.
Next week we will be covering ISO, and how we bring Aperture, Shutter Speed & ISO together to make great photos.
If you have any questions or concerns on the post, feel free to email us and we will be glad to help you. Or feel free to email us any questions you may have about photography and we will be sure to work them into another how-to post.
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(and comments are always appreciated!)