Understanding Light and Shutter Speed

Photography is dependent on light. In the oldest days of film, we did not have artificial light (candles weren't enough to create exposure and were more likely to cause a fire than help you out). Photographers were limited to shooting outdoors and even when the first flashes were made, they were not that effective. So how did they compensate for this lack of light? They used very slow shutter speeds.

Shutter Speed and Film

Light burns an image onto film. There are two ways to control this on your camera. Adjust your exposure, which means you allow more light to enter through the lens. Or, you would slow your shutter speed down which means more time is given for the image to burn. That's why people had to sit still for a few minutes to get their pictures taken. If you look at old Civil War group shots, you can see a couple of blurry faces. That's because these people moved during the exposure process.

Shutter Speed and Digital Cameras

Today's film has been replaced with the image sensors of your digital camera, but we still use shutter speed to compensate for light. Night photography is one instance. Rather than raise the ISO, your camera slows the shutter speed down to make up for the lack of light. That's why your photos sometimes look blurry when you shoot handheld. If you need to use a slow shutter speed, then you should shoot with a tripod.

Keep in mind that you can speed up the shutter to compensate for too much light as well. But, generally the settings for speeding up are limited and there are more options to slow it down.

Shutter Speed and Motion Pictures

In still photography, we use shutter speed to compensate for light. In motion pictures, we adjust the shutter speed to produce the special effects of fast motion and slow motion. A video camera shoots 30 frames per a second. So, in one second, it shoots 30 images. If you want to shoot real slow motion, then you need to shoot the action at high speed so it will play back slowly at 30fps. This means that your shutter will be speeding faster and the individual images have less time to be exposed. To compensate, you need to add more light than you would need for normal shooting speed.

The opposite of this is shooting action that will be played back at high speed. Since you may be only shooting 15fps, you need to compensate for the slower shutter speed by having less light. 

The Relationship of Light and Shutter Speed

So shutter speed determines the length of time that the image is exposed to light. A slower shutter speed is used for situations with low light and a faster shutter speed is used to compensate for situations with too much light.

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