Shutter Speeds: A Slice of Time

It's called still photography, as opposed to video photography, but every photograph is actually the record of a tiny slice of time; if it looks still, it's just an illusion.

Luckily for us, shutter speeds make a lot more sense than f-stops and are more self-explanatory that film speeds, however, like these other exposure settings, shutter speeds in general follow the same doubling and halving pattern. Typical shutter speeds are expressed on cameras in the following order:

2000 - 1000 - 500 - 250 - 125 - 60 - 30 - 15 - 8 - 2 - 1 - B

What do these mean? These values represent fractions of a second. 2000 represents 1/2000th of a second (a very small slice of time). 2 represents half a second (a relatively long period of time in daylight photography). Obviously, 1/2000th of a second allows twice as much light to hit the film as 1/1000th of a second. As we know from apertures, a doubling or halving of the amount of light is known as a stop. But, like f-stops, different shutter speeds have different effects on your resulting images. These effects are less pronounced with still subjects than in images that contain some kind of movement but as our world contains movement seemingly everywhere you should be aware of these characteristics. The characters of different shutter speeds can be roughly divided into two; technical and creative characteristics.

Technical

Avoiding camera shake using shutter speeds

One of the main technical concerns when choosing the shutter speed to use is the control of camera shake. We've already learned that a still image is actually a record of a slice of time. If, during that period of time the camera moves relative to the subject the resulting image may not me sharp depending upon the amount of movement and the amount of time. What does this mean? When it comes to hand holding a camera (anytime your camera is not on a physical support such as a tripod) I don't know of anyone who take a sharp image at half a second without help.

It is a source of machismo pride among photogs how slow a shutter speed they can hand hold their camera and still get a sharp image. You might be able to hand hold your digicam at 1/15th of a second and get a sharp image but for me it will only be one in three images that don't exhibit camera shake. I'd much rather use 1/60th or better yet, 1/125th and get more consistent results. Basically, the faster the shutter speed, the easier it will be to hand hold your camera.

So how fast is fast enough? It depends on the camera and the focal length of the lens. The old adage used to be that your shutter speed should be faster than your lens' focal length and as a basic rule that still holds true today. In the 35mm film world this means a shutter speed of 1/60th or faster would be appropriate for a standard 50mm lens. For a 200mm telephoto you should use 1/250th of a second or faster. This rule will help you get images without camera shake but you still cannot be sloppy about your technique. Take a page from target shooters: before taking the shot brace yourself and your camera. This means, if you are standing, take a wide, strong stance. If you are holding your camera at eye level, lock you elbows and brace them to your body. One hand should be supporting the full weight of the camera preferably underneath you rig's center of balance. The other should be used to steady the camera and press the shutter. Breathe shallowly and smoothly. If you can, immediately before you press the shutter hold your breath.

When you do press the shutter squeeze it don't jab at it. For this reason it is important to know exactly where in your camera's shutter release button's stroke the actual shutter fires. With many modern cameras half pressing the shutter has some effect; it may stop down the lens, trigger the camera to focus, lock the exposure - any combination or all of these actions may result. Pressing the shutter a little more usually results in the shutter actually firing. It's important that you know exactly what "a little more" for your particular camera is. Triggering the shutter should never be a surprise. You should know prescisely the moment the shutter will go off. If your camera is a digicam with significant shutter lag this is easier to say than do but practice helps. With a new film camera dry fire it with no film until you know exactly how your shutter behaves. With digital cameras it's fun to learn how your shutter behaves by taking shots of the TV. Switch to a sports game or action movie and shoot away. What you see when you review your images in your LCD screen should be just what you anticipated when you pressed the shutter. It's also good practice for anticipating the moment as well as getting to know your shutter.

There are other variables that can affect camera shake. Putting the camera on a solid tripod or stand may let you get the exposure you need using a slower shutter speed but you still must be vigilant. Make the support as solid as possible. Lock the head (all axis) of your tripod. The wider the legs the better. Don't use the central column of your tripod unless absolutely necessary (it's like balancing a monopod on top of your tripod). When you trip the shutter of you camera on the tripod try to isolate yourself from it; a cable release or remote is great - using the self timer of your camera works as long the precise moment isn't that important.

Forces external to the camera are not the only thing that can cause camera shake. With SLR's you mirror swinging up out of the way of your shutter can cause shake too and this can be especially hard to deal with. Camera manufacturers try to dampen this effect as much as possible and with many modern cameras shake cause by mirror slap is a non-issue. However, with some older, larger, mechanical SLR's it can be a problem at slow shutter speeds. For this reason a lot of professionally featured SLR's have a mirror lockup feature. This is only really useful when you are taking longer exposures, when the camera is not hand held and when it is not important that you be able to see the image through the viewfinder immediately before the picture is taken. Mirror lockup allows you to move the mirror out the way of the shutter before you even press the shutter. Of course, with the mirror locked up against the bottom of the view screen the viewfinder is now black but mirror slap will not be a problem.

With cameras other than SLR's like rangefinders, digicams and TLR's now mirror is moving and it can mean you might be able to hand hold your camera a full stop slower than your SLR. This is one reason that Leica has such a great reputation as a low light camera. There are other technological features that may allow you to hand hold your camera at slow shutter speeds than you would otherwise be able to. Principle among these is image stabilization. Image stabilization. is a feature built into some lenses and some camera bodies that anticipates the movement of the camera (camera shake) and compensates for it. Some people claim this can give you 2 or even more stops, however, it can be an expensive feature.

 

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