It's when you combine virtually identical multiple exposures, "stacking" them to reach a final image that has a total exposure time equal to the sum of the individual exposures.
It's useful in astrophotography for a number of reaons. The main one is that a bunch of short, say 6 individual 30 second exposures, can be combined The result is the accumulated photons of a 3 minute exposure. The neat thing is that tracking error (irregularities in the motor drive or polar alignment) can be virtually eliminated, because software automatically aligns/registers the individual images so they overlay each other perfectly. The additional benefit we're talking about here is that the sensor can be run at both a lower ISO and for a shorter exposure duration, both of which reduce noise. Tom C. >From: "Shel Belinkoff" <[EMAIL PROTECTED]> >Reply-To: Pentax-Discuss Mail List <[email protected]> >To: "Pentax-Discuss Mail List" <[email protected]> >Subject: Re: K10D aimed as D200 killer/Translation of interview >Date: Tue, 31 Oct 2006 15:38:30 -0800 > >What's a "stacked image?" > >Shel > > > > > [Original Message] > > From: Tom C > > > It also is likely possible to reduce > > overall noise by shooting at shorter > > exposure times and stacking images. > > The stack will stack up noise just like > > it does with the signal, but if each > > stacked image is less than half as > > noisy as it's double-ISO cousin, > > results could be favorable. > > > >-- >PDML Pentax-Discuss Mail List >[email protected] >http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
