When making a long exposure, it’s really easy to keep the shutter open for a lengthy time period. This might be because you want to shoot in lower light or to pull off an exposure which stretches time out a bit. In either case, the chance of seeing streaking is increased.
Using a cable release (or your self-timer if you don’t have a cable release) will help reduce camera shake. A remote can be wireless or connected via a cable. A remote may have additional features such as an intervalometer for time-lapse shooting or the ability to adjust camera settings. If youre choosing one for HDR or landscape, a basic model will do.
The goal is to reduce the amount of camera shake. Some of this is caused by touching the camera body. Additionally, if you use an SLR camera, lock up your mirror at speeds between one second and 1/60th of a second to eliminate mirror flap, another common cause of vibration. If you forgot your cable release or remote but don’t want to induce vibration with your finger tripping the shutter, use your cameras self timer.