Originally posted by jbinpg @nozoom - Not true if your frame includes any specular subjects such as stars against a dark background. Any slight movement will be recorded as a squiggle no matter how short the movement compared to the duration of the whole frame.
I agree to that. Thank you for reminding me. For most "ordinary" long exposure pictures, hand operating the shutter release button will be sufficient. Important specular highlights (or more general important burnt out highlights) might require more carefulness if sharpness is important and stars will also require not only an ordinary tripod, but one with an equatorial mount.
I would however not use interval composite mode for long exposures if pin sharp specular highlights is important. I would use B (for bulb) and remote MUP (for mirror up with remote control). Then, the first press would rise the mirror, the second open the shutter and the third close the shutter (and lower the mirror). Otherwise you run the risk of the mirror shaking the camera and blurring the highlights.
Examples of "ordinary" long exposures could be softening water in waterfalls or softening waves on a beach, or for removing traces of people in open spaces or in front of a building, creating trails of lights from traffic in a cityscape or landscape lit by moon light.