How to: Use long exposures for interesting shots
Using a long exposure can enable some really interesting shots that can convey motion. What happens during a long exposure shot is that the shutter remains open for a long period of time which allows the image to “burn into” the sensor longer. When there is motion during the exposure, that motion will be blurred. When used well, you can achieve some really interesting shots with this technique.
While I find it is easier to get the overall desired result when using manual mode so that you can control the final exposure better, often you can get the same effect with either shutter priority or aperture priority modes and then tweaking the exposure with exposure compensation.
Let’s start with the first image above. I wanted to show the cable car turnaround in San Francisco and convey the motion that occurs when they rotate the car around to the uphill track. Since it wasn’t very dark out yet, I had to knock down as much of the ambient light as possible to enable a long shutter time. If I would have had a neutral density filter, I could have used that but I didn’t so I had to make due with camera settings. First off, the ISO was dropped as low as it would go which in the case of the Sony NEX 5n is 100. Since the lower the ISO number, the “less sensitive” the sensor is to light, the lower the ISO, the less light will be captured. Since a long shutter will let in a lot of light, the only other way to control light is to use the smallest aperture setting. In this case, the highest I could go was f/22. Since I wanted this to look somewhat like a daytime shot, I could now adjust my shutter speed. My camera told me the right shutter for a good exposure was four seconds so we set up the camera on a tripod and took the shot.
In this example I wanted to see the lights of cars whizzing by. The camera told me that the right exposure was eight seconds. However, at eight seconds, the scene looks like daylight when what I wanted was to show that the image was taken at night. In order to reduce the amount of light and make the scene look darker, I sped up the shutter from what the camera suggested up to five seconds. While the end result wasn’t exactly what I wanted, it did demonstrate the technique quite well.
Getting Your Timing Down
If there is any real “trick” involved here it is in setting the shutter speed to get the desired result. The way I do it is to time the event I am going to shoot. When I did the cable car, I actually got pretty lucky and the exposure meter saying four seconds was exactly the effect I wanted. In the case of the street, I timed that it took five-seven seconds for cars to leave the intersection and get out of the camera’s view. Using the time that I wanted to record as the shutter speed, I could then adjust the other camera settings to give the exposure that I wanted.
Do you have any good long exposure shots that you have taken? If so, share them in the comments below.