Long Exposure Noise Reduction - Canon

[bjk896]

The old 300d died after many a star trail trip, to be replaced by a Canon 760D. I will continue my Star Trail life but wondered - without the experience yet - whether any of you have thoughts on the 760D's noise reduction action
My instinct is NOT to use it because I believe it takes a "long" time to process. Does it process and write to card during exposure time of next shot or process and hold up next exposure until it has done its thing?
How long is the "long" process time which I presume is a sort of dark shot Vs live shot analysis.
What occurs if set to "Auto". The real question is does it compromise the Star Trail continuity.

[James G]

I'm no great experet on this but if you are photographing star trails I would not use the internal noise reduction process.

My understanding is that it holds up the ime before a second exposure.

I rarely shoot star trails but I do shot objects like the moon and the orion nebula. I usually create my own dark frames and shoot multiple exposures and then use PS and or Registax to align and blend images, also to remove noise (by stacking and then opacity blending).

[DanK]

Brian,

I use Canon's long-exposure often in my night photography. It works well. However, it wouldn't use it for star trails (which I don't do). It takes a second black-frame exposure exactly as long as the first and subtracts from the first active pixels in the second. So, if you were taking a serious of shots, half of the time interval will be blacked out by the long exposures.\

Astrophotography stacking programs are probably the way to go, but since I don't do that type of night photography, someone else will have to weigh in about those.

Dan

[revi]

My understanding is that the frames used for black frame subtraction don't have to be taken at the same time as the images. You do need to have them for about the same conditions (exposure time and perhaps temperature), so you might try taking one black frame at the start and one at the end of a series of pictures, and then do the subtraction in post.

And yes, the in-camera long-exposure noise reduction does interrupt the series, so you'll end up with interrupted trails (dashes, with light and dark sections about equal).

Part of the long-exposition "noise" is caused by "warm" pixels, that gather signal during a long exposure independent of the incoming light but depending on the time the sensor is gathering signal (that's why blackframe subtraction works in the first place). So the camera has no choice but do that black frame exposure after every image (if only so it can discard the black frame after use to free the internal buffer).

[bjk896]

Thanks to all and, Revi, your second para was what I thought would happen and 1-3 seconds between long exposures is just enough without added process time.

I've been too busy to play seriously with the 760 but liking everything I've seen so far.

[george013]

Thanks to all and, Revi, your second para was what I thought would happen and 1-3 seconds between long exposures is just enough without added process time.

I've been too busy to play seriously with the 760 but liking everything I've seen so far.

Try this peace of freeware: deadpixeltest. It also shows you the hot pixels, or noise. You'll get an idea of how much your camera is producing with different time and iso.
http://www.photo-freeware.net/downlo...ad-pixel-test/

George