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p.1 #16 · p.1 #16 · // Significant color noise during long exposures // | |
Greg Campbell wrote:
The in-camera reduction works much the same way, but requires the camera to take an equally long dark exposure immediately after every 'real' exposure. This delay can be annoying.
A few points.
You are absolutely right that the dark frame exposure method (Long Exposure Noise Reduction, or LENR) increases the time spent exposing each photograph. If you are doing a 10 minute exposure for your photograph, the ensuing dark frame exposure takes another 10 minutes — a total of 20.
Is it worth it? The answer is a bit subjective and each photographer will have to decide.
Since the in-camera dark frame exposure always has exactly the same settings as the original photograph it is likely to be more accurate than the method described above in a previous post, which uses benchmark photographs made at a different time and perhaps under different conditions (e.g. temperature) as the starting point for determining the data to be subtracted from the frame.
Looked at one way, the doubled exposure time (regular exposure + dark frame exposure) is an annoyance or a problem, especially since you are most likely to need it with the longest exposures. When I mentioned a 10 minute exposure taking 20 minutes I selected those times because they are in the range where you might want to employ LENR. Make a 30 minute exposure and you are talking about spending one hour.
That may be bad, but because digital cameras do not suffer from reciprocity failure in the way that film cameras do, the exposure times are still shorter than they were back in the good old days of film. In addition, if you are getting the R, G, and B hot pixels in your long exposure images, and you are trying to produce high quality work, the time is worth it. And for really long exposures there are alternatives, including blending multiple shorter exposures.
One time some years ago I made a few long exposures using LENR while on a backpacking trip into the eastern Sierra Nevada. It was a very dark night, lit only by less-than-full moon light, and I think that exposures were in the 14-15 minute range. Each photograph took over a half hour by the time I set things up, composed it (in the dark), selected camera settings, completed the main exposure, and then waited for the LENR dark-frame exposure to complete. I was initially frustrated by the delay. But then I found a comfortable place to sit along the edge of the lake, sat back, and enjoyed the deep quiet and stillness of the night. (It did not turn out to be one of my best night photographs, but that's the way it goes.) :-)
Dan
http://gallery.gdanmitchell.com/gallery/var/albums/NaturalWorld/TheLandscape/California/SierraNevada/OtherSierraNevada/BlackAndWhite/ThousandIslandMoonCove20070727BW.jpg
Edited on Jun 25, 2015 at 04:34 PM · View previous versions
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