Monday, March 1, 2010

Shutter Speeds and Capturing Motion (Exposure part 2)

This is part four in an ongoing series of things I'm learning in my photo 1 photography class. You can find the first three posts here:

-Photo Basics - Basic Definitions
-Photo Basics - Camera Controls and White Balance
-Aperture and Depth of Field (Exposure part 1)

So, in my last post I talked about how a camera is basically a light tight box and how the aperture and the shutter work in conjunction to control the amount of light that enters your camera. The intensity of that light is controlled by the aperture and the time interval it does so is controlled by the shutter. In that post I went on to talk about aperture in particular and how it controls the depth of field. Today I want to talk about shutter speeds and how the shutter controls motion in your pictures.

Some examples (albeit not very good ones):

The shutter is a piece inside the camera that blocks light from reaching the light sensitive material (the film or the sensor) until you press the shutter button (that “click” noise you hear is the shutter). When the shutter opens, light then passes through the lens and strikes the film or sensor, recording the photograph.

The longer the shutter stays open the more light enters the camera. The shorter the shutter stays open the less light enters the camera. The amount of light allowed to enter your camera will determine how exposed your picture is. (Remember, too much light = overexposed and not enough light = underexposed.)

The time interval between the shutter's opening and closing is called the shutter speed. Shutter Speed is measured in seconds or fractions of a second. Example: 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1, 2, 4, 8 and so on. On some cameras, the “1/” is assumed and the setting for 1/1000 would simply be “1000.” The important thing to look out for is the two small dashes (like when denoting an inch) next to the full second settings. While 1/1000 would be denoted as “1000,” 1 full second would be denoted as 1. Similar to how moving the aperture one f-stop either doubles or halves the amount of light, moving one shutter speed wither doubles or halves the time the shutter stays open.

Here is a great video I found on youtube:

So, the real question is why do we need to know any of this? Well besides exposure, the shutter speed conveys the motion of the subject in your photo. The examples I posted above all show movement. You can actually see what was moving faster then my shutter time because of the blur. Even though we all tend to think blur automatically equals bad, this is not true. As long as you are in control of your camera, a little blur can actually go a long way.

Here are two comparisons of the same situation but with slow vs. fast shutter speeds:

A slow shutter speed (meaning, the shutter remains open for a longer amount of time) lets in more light and results in blurred motion. Just think about how much movement your camera would catch if you left the shutter open for a full second. On the flip side, a fast shutter speed (meaning, the shutter remains open for a fraction of a second) lets in less light and freezes action. (As you can see by this video, a shutter speed faster then 1/60 is faster then what the eye can even see.) As the video above pointed out, it's important to keep in mind that a shutter speed of "1/60" is usuallly the slowest shutter speed you can use and still hold the camera steady at. Anything slower then "1/60" will be blury to some extent (because of you not because of the subject) and will require a tripod (or a stead object). Of course this isn't always true, but it's a good general number to keep in mind.

There are some pretty cool effects you can get with trying different shutter speed. One effect is called panning. Panning is basically where you keep a moving subject in the same place of your frame while using a slow shutter speed when taking the picture. The result is a blured background with a clear subject.

Here's the only halfway decent shot I got using a shutter speed of 1/20 (it takes a lot of practice):

You can also see some amazing pictures using slow shutter speeds here. (Seriously, they're amazing.)

I personally found our shutter speed assignment to be much more difficult then our depth of field one. Not only did it feel kind of unnatural for me to try and capture movement, but it also takes a lot more practice. It's pretty hard at first to be able to guess the perfect shutter speed for what you're trying to capture. Freezing action is easier since you can just choose a fast shutter speed, but trying to control movement took a lot of practice (and will take a lot of practice). It also takes practice to understand how to make your shutter, aperture, and ISO work together (I plan on posting on this next).

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