Now that you've got a pretty good handle on your camera's scene modes, you're also starting to develop an understanding of the basic principles of photography - the ones that are going to take you from the land of snapshots to the land of technical excellence. You've already seen these principles in action, now it's just time to define them and look at how you can fine tune them to create the images you want.
This image was shot at a shutter speed of 1/5th of a second.Antwerp: Mas (escalator) by Flickr user *katz
The first of those principles is shutter speed. You've already used shutter speed to capture particular sorts of images in particular situations, but you've done it under the guise of a scene mode. "Sports" mode, for example, is really just an automatic setting that sets your camera up to take photographs using a fast shutter speed. "Night" mode, on the other hand, typically uses a slower shutter speed. But both of these settings are limiting, in that they don't allow you to choose a specific shutter speed, which might occasionally result in an image that does not look like the one you envisioned in your mind. Now is the time to get a solid understanding of what shutter speed is, how it affects your photos and what speeds you should use in various situations.
What is shutter speed?
All cameras are simply tools for capturing light. Light rays are constantly bouncing around in our environment, reflecting off of the objects around us in all different directions. A camera's lens focuses these rays and then projects them onto the camera's sensor, creating a photographic copy of a scene. Now, in order for this to work, a camera needs a shutter. Think of this just as you would an old-fashioned shutter in a home - to let in light, you open the shutter, to shut out light, you close the shutter. A camera's shutter works in exactly that same way - when you're ready to make the exposure, the shutter opens, then it closes again after (hopefully) allowing just the right amount of light to reach the sensor. Your shutter's speed is what determines how much light is allowed in - if the shutter speed is too fast, you'll get an underexposed or too-dark image; if it's too slow you'll get on overexposed or too-bright image.
Of course, that's not the only effect shutter speed has on your photographs. Shutter speed is also used to freeze a fast-moving subject, or to blur that same fast-moving subject, depending on your goals.
How do I know which shutter speed to choose?
The first reason is purely technical. There are certain situations where you don't really have a choice - you have to use a fast or a slow shutter speed or you simply won't be able to capture the shot. There are other situations, though, where you will want to choose your shutter speed based on your personal vision for the image - this is when shutter speed becomes an artistic choice, and the choice you make can mean the difference between a mediocre photo and an amazing one.
Some basic guidelines
A slow shutter speed can mess up an otherwise good image. It can also be magical. So how do you know when to choose what shutter speed? Well, you can start by following some basic guidelines.
In some cases - particularly low light situations - you may not really be able to choose your shutter speed. When you're shooting in the near-dark, you will have to select a slower shutter speed because a fast shutter speed isn't going to let in sufficient light to make the exposure. Low light means slow shutter speed, which may also mean that you need a tripod or something to prop your camera on or brace it with - something else to keep in mind when experimenting with your camera's shutter speed. At very slow speeds, you won't be able to hand-hold your camera without adding camera shake, which is that motion blur that happens when your shutter speed is slow enough that it actually records the slight motion in the hands of the person holding the camera.
Dimly-lit scenes often include some motion blur. This one was shot using a 10 second shutter speed.india. haridwar 38 by Flickr user deep_schismic
A fast-moving subject demands a fast shutter speed - most of the time. If you're trying to photograph a racehorse, for example, you will want to select a shutter speed in that 1/500+ range. This will freeze him mid-stride and may even freeze those dirt clods he's kicking up behind him as he races towards the finish line. But take care - there may be other situations where you'll want to have a little motion blur in your fast moving subject. Racecars, for example, may be passing you at blistering speeds but if you shoot them with a fast shutter speed it might look like they're all parked there together on the track. In this situation you may want to slow down your shutter speed and capture a little bit of motion blur to convey that sense of speed.
To freeze the action, this photographer used a shutter speed of 1/800Untitled by Flickr user * raymond
Deliberate Motion Blur
Which brings me to this next guideline: deliberate motion blur. I'm sure you've seen those images of misty-looking waterfalls or city streets full of blurry pedestrians - both shots are accomplished using a slow shutter speed (the misty waterfalls do require additional special equipment, though).
To capture deliberate motion blur, you'll need to set your camera up on a tripod and then slow down your shutter speed - stationary objects like buildings and rocks will render sharply in your final image, while moving subjects will be blurry. How blurry depends on how quickly they're moving, and how slow your shutter speed is. For slight blur you may not need to go slower than 1/30th or 1/15th, depending on the speed of your subject; for motion trails you could go longer, how long depends on how much motion trail you want to capture. Too long, though, and you may actually erase people from your scene altogether - if they're moving quickly enough, the camera won't even register them.
Misty waterfall scenes like this are shot with long shutter speeds, but you'll need extra equipment to capture a shot like this during the day.Waterfall by Flickr user brentdanley
Scenes with large depth of field
Landscape photographers often want to capture images with as much depth of field as possible, which means a smaller aperture. Smaller apertures let in less light, and therefore call for longer shutter speeds. That's why you generally see landscape photographers with tripods - even during the day you may not be able to hand-hold your camera at those smaller apertures/longer shutter speeds.
Small apertures require longer shutter speeds.The Rope of Life by Flickr user Rickydavid
Shutter speed can be really fun to experiment with, so experiment away. Try shooting a single scene/subject with a fast shutter speed, and then again with a slow one and compare the difference. Sometimes slow shutter speed can be very effective in creating mood and drama, sometimes it just doesn't work at all. The best way to find out is to do it both ways and compare. Have fun!
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