Originally posted by MarcusCalidus Long exposure vs Average Interval Composite
Very interesting post.
Originally posted by MarcusCalidus I once read somewhere that the noise would increase the longer the exposure takes. So I guess the Average Interval Composite mode would be the go to choice?Then however since the minimum interval time is 2 seconds you'd loose the trail of slow moving objects.
Hum yes. In conposite stacking there's a trade between exposure time and the time lapse between two frames where the continuity of subject motion is lost such that composite doesn't render as smooth as a single longer exposure. For example with moving water, stacking approximates a smooth exposure only with a large number of frames stacked ( x 10 exposures or more). For slow moving clouds , the time lapse between exposures (set to "minimum" in the K1) is negligible relative to cloud motion.
A few things to consider:
- I don't think that stacking improves dark current noise of long exposures because dark current noise is proportional to exposure time but it is mostly not random so it is not eliminated by the stacking. Long exposure noise reduced (LENR) is not recommended in a composite capture because of half time require to capture and remove dark frames. If LENR should be performed on a stack, it is preferable to take a black exposure with the lens cap on, and perform LENR on each frame before stacking at post processing (adding frame off-camera).
- composite stacking bring the benefit of lowering read noise, so stacking 2 shots at ISO100 is more like getting better than the image quality of an ISO50 sensor. Stacking improves read noise so much that it can exceed the max S/N of 8bit JPEG which produces banding in skies or any image area with low change in tonalities.
- frame alignment is not performed with in camera composite exposure, any camera sensor micro-displacement induced by mirror and shutter up-down slightly reduce the resolution of the stack
- if the shutter speed is too quick without ND filter, the number of frames required to emulate a long exposure may be an overkill, better use a weak ND in that case.
So typically, stacking 4 to 8 images in live view mode, at ISO100, produces stunning image quality. More than 8 frames stacked create banding in JPEG (unless noise is added again when exporting the RAW to JPEG).
I use composte so that I carry only two ND filters for long exposures. I use a weak ND filter and if the exposure isn't long enough I stack frames. If the stacked frame total exposure time is not enough I use a 10 stops ND and if not enough I use multiexposure again. I hope you find my comment helpful.