Which image do you prefer?
Or
The difference is produced by choosing shutter priority rather than the program mode.
Shutter speed is a little simpler to describe than aperture – is is simply how long the shutter allows light to strike the film or sensor.
When set in program mode, most cameras have an infinite number of steps of shutter speed between the shortest & longest available. Depending on the type of shutter, a typical point & shoot digital camera will have a range from about 1/2000 of a second to 8 seconds. Digital single lens reflex cameras often have a wider range – for example, the Nikon D300 (an $1800 DSLR) has a range from 1/8000 of a second to 30 seconds.
When operated in shutter priority, most cameras adjust shutter speed in steps; how many usually depend on the price of the camera. Typical point & shoot provide 1 stop steps, DSLRs may provide 1/2 or 1/3 steps. Doubling the shutter speed provides the equivalent of additional stop of light. Typical steps for a point & shoot camera would be 1/2000. 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8.
When you choose shutter priority (usually by selecting “S” on a mode dial or menu) the camera’s metering system will select the aperture that provides what it determines is correct for the film speed or sensor ISO setting. Choosing a fast shutter speed requires a wider aperture; slower speeds will stop down the aperture.
Click on “Read the rest of this entry” to see some reasons for using shutter priority.
Some reasons you may wish to choose the shutter speed rather than leaving it up to your camera:
- There is a “rule” for shooting handheld – “The shutter speed must be faster than the reciprocal of the focal length of the lens.” What that means is if you are shooting with a lens that has a focal length of 100mm, you should use a shutter speed above 1/100th. A 500mm lens requires a shutter speed above 1/500th. Of course there are photographers that can handhold a camera better than others and many new digital cameras have image stabilization built in, but it is still a useful rule. Ignore it and you may end up with blurry images due to camera shake. You may never see camera shake on the camera’s LCD screen, either because of limited resolution or small size. You may only discover the problem when you view the image on a computer screen or make a print. That may happen well after you no longer have the opportunity to reshoot the image.
- If your subject is moving rapidly a fast shutter speed will often freeze the motion. There are additional techniques to “freeze” an image such as panning (moving the camera so that the subject stays in the same place in the viewfinder throughout the exposure) but panning is difficult if the camera uses an electronic viewfinder that shuts off during exposure (or even worse, has no viewfinder.)
- You may also want to choose a slow shutter speed to purposely blur an image. Photographs of waterfalls or moving streams can often be improved using a long exposure. Of course, once you exceed the focal length vs shutter speed rule you need to use a tripod. An example of each is shown at the beginning of this entry. The first was shot at 1/50th of a second, the second is a 2 second exposure. Again neither is “correct” however I find the second more interesting.
- Another use of long exposures is to remove moving objects from your image. It is a bit tricky in that the lighting must be fairly even across the scene, but if you take an 30 second exposure of a bunch of people walking around and they are all moving, they disappear because they are never in one place long enough to be properly exposed. The background doesn’t move so it ends up properly exposed. Of course the longer someone stands still the more visible they become. The technique can produce some interesting photographs.
- An extension of this is to photograph moving traffic at night using long exposures to get streaked headlights & taillights.
There are a couple of “gotchas” at either extreme of shutter speed. Very long exposures will cause color shifts with film & digital cameras. In addition, long exposures add noise to digital images. Some cameras have built in noise correction, in other cases it can often be corrected during post processing. For extremely long exposures (1/2hour+) I’d stick with film.
Short exposures may not work with flash. Depending on the type of shutter your camera uses, shutter speeds much shorter than 1/250th of a second will catch the shutter as it opens or closes. If part of your image is black & the rest properly exposed, this may be the cause. Your manual should give the maximum shutter speed when using flash.
Just as I suggested in the aperture priority blog entry, if you are using a digital camera you have no excuse not to experiment with shutter priority. You may take a bunch of “duds” but that is the only way you discover new techniques on your own.