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06-18-2009, 04:36 AM   #16
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Okay, that makes sense. There's no magic involved, it's just deferred.

06-18-2009, 07:05 AM   #17
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QuoteOriginally posted by Duck Dodgers Quote
Okay, that makes sense. There's no magic involved, it's just deferred.
you may just call it deferred. but it makes lots of difference imo. for example, when taking shoots with fireworks, users can shoot with no wait between frame. Just hope pentax can implement this in the future.
06-18-2009, 02:13 PM   #18
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I stand corrected. Quite clever, even if as was noted in the referenced thread, it doesn't actually work as well as doing it right away.
06-18-2009, 02:35 PM   #19
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Are we still talking about dark frame subtraction? Does the 5D abort the dark frame, and continue later if interrupted or what?

06-21-2009, 05:35 AM   #20
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QuoteOriginally posted by Marc Sabatella Quote
Dark frame subtraction is not about hot pixels. It's about noise. True, PP programs can remove noise too, but the specific method use in dark frame subtraction is quite effective for the type of noise it removes, and it is *not* available in Pp (unless you happen to have an appropriate dark frame you can use, and the program supports it - most probably don't).
Noise is random and varies between shots. There's no way a dark frame can be used to reduce noise. Dark frames can only be used to detect hot pixels.
06-21-2009, 08:45 AM   #21
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QuoteOriginally posted by patrickhh Quote
Noise is random and varies between shots. There's no way a dark frame can be used to reduce noise. Dark frames can only be used to detect hot pixels.
I studied long exposures with the K20D. As it turned out, there are a number of pixels in relatively constant locations which turn "dim" in long exposures. Still, too many and too variable to be mapped out. BTW, not specific for K20D. In my German forum, we even ran statistics between users and models to count their numbers below specific thresholds. Such dim pixels may escape to be detected as hot if they are not bright enough.
06-21-2009, 05:08 PM   #22
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QuoteOriginally posted by patrickhh Quote
Noise is random and varies between shots. There's no way a dark frame can be used to reduce noise. Dark frames can only be used to detect hot pixels.
I guess that depends on what you mean by "hot pixels". There normal meaning of this is pixels that are permanently stuck on 100%. That's not what is going here, though - we're talking about pixels that simple read a bit brighter (or darker, I suppose) than they should. This comes out looking like noise, not like the "hot pixels" we normally associate with that term.

See:

Dark frame subtraction - Wikipedia, the free encyclopedia
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