Last month we discussed choose aperture or f-stop settings and their relationship to depth of field. This month, we are going to discuss the companion to choosing your aperture: how to choose your shutter speed. Almost all single lens reflex cameras, as well as many point and shoot or the more modern digital cameras will give you the ability to choose your shutter speed. This is often called "shooting in shutter priority". This simply means that you choose the shutter speed, which you are making the priority for the camera, and the camera will use this information to choose the other complementary settings to create a properly exposed photograph.

Shutter speed is important for several reasons. The main reason one would want to choose the shutter speed is to determine whether any action taking place in the photograph is "stopped", meaning that it appears clear and detailed, or if the action will be blurred. There are good reasons for choosing both options.

When photographing a sporting event, it is often advantageous to "stop" the action. Let's say that your son just scored his very first touchdown. You want to see him running into the end zone and you want to be able to see his smile clearly. So, you would choose a "fast" shutter speed. 

Shutter speeds are marked in fractions. A shutter speed of 1/1000 means that the shutter is going to open and close in a single thousandth of a second. And only the action that took place in that 1/1000 of a second will appear in the photo. Thus, your son's legs won't be blurred when he crossed into the end zone, and you'll capture that smile in perfect detail. Generally speaking any shutter speed higher than 1/250 will be excellent at stopping action.

So, now that we know that choosing a shutter speed can stop the action and give us a sharp photograph in the middle of a sporting event, why would we ever want to use a slow shutter speed? Have you ever seen a picture of a waterfall where the water looked like a single stream, almost like a web of cotton candy? And the water has an effect that seems as if you can "feel" the movement as it cascades over the rocks.

Placing the camera on a tripod and choosing a slow shutter speed create this effect. When I am trying to create this kind of effect, I will often "bracket" my exposures. This means I will take several pictures, at different shutter speeds or exposures. I can then look at the finished results and determine which gives me the best effect of the running water. (You can also bracket exposures when shooting in aperture priority. This will allow you to determine which exposure gave you the best depth of field for your purpose.)

Any time you use a shutter speed slower than 1/60th of a second, you need to use a tripod or a flash unit. It is generally not possible for someone to hold a camera steady enough to get a good picture at these slower shutter speeds. 

It is important to note that most flash units preset the shutter speed for you. The camera and unit will interact to choose the shutter speed designed by the manufacturer for us in flash photography. So, when using a flash, you do not have control over the shutter speed. (Some more technical units will give you control over the aperture setting, but these are high end, expensive flash units). However, it is also important to note that using a flash unit will stop almost all action. So you can gain the same result as if you had not used a flash but had used a higher shutter speed.

You've probably seen examples of this in nature. If you have ever seen a bolt of lightening illuminate the sky, you've probably also noted how anything moving at the time the lightning came seemed to halt in place. This is the same principle as how the flash unit will stop action.

So, how do you determine which shutter speed to use? A lot will be determined by the lighting conditions and the kind of film you use. If stopping action is important to you, use a "fast" film, which requires less light for the pictures to be exposed. Good examples of this would be ISO 400, 800 or 1000. If you have a very bright and sunny day, you can also stop action with ISO 200, or even 100 film. Having said that, I do recommend using nothing "slower" than ISO 200 film when you need to stop action. 

Also take into consideration how fast the object you wish to get a picture of is moving. A racecar will require a faster shutter speed than a five-year-old daughter playing soccer. For very fast, generally mechanical objects, I recommend a shutter speed of 1/1000 or faster. For kids sports, dramatic productions, etc., a shutter speed of 1/250 - 1/1000 will be sufficient.

And for those times when you want to blue part of the detail in your picture, choose a shutter speed of 1/30 or slower. Many SLR cameras have a setting of "B", which stands for bulb. When using this setting, you attach a shutter release to the camera, and place the camera on the tripod. You can use the release to set off the shutter without touching the camera, thus insuring a picture that is not affected by your body movement. And, then you can leave your shutter open for indefinite periods of time. This can be excellent for many forms of nature photography including waterfalls or astronomy pictures.

Finally, remember that your faster shutter speeds, result in larger aperture openings. This translates into stopping action but having less depth of field. So you will need to focus very accurately for your pictures.

Good luck and happy shooting.