time exposure

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A photographic exposure made by leaving the shutter open a relatively long time, generally a second or more.
• noun An image so made.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun photography An exposure made by leaving a camera's shutter open for a period greater than a fraction of a second; an image so obtained.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun exposure of a film for a relatively long time (more than half a second)
• noun a photograph produced with a relatively long exposure time