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I have never shot with intervalmeter for the purposes of image stacking but want to at least try. I am going to try star trails but my question is this: Should I turn off in-camera long exposure noise reduction when shooting for image stacking?

When i shoot at night and the the in-camera long exposure noise reduction is on, the process often takes minutes before I can shoot again. If I want to shoot continuous star trails would this create gaps? If I turn the long exposure noise reduction off I should be able to shoot continuously without the extra pause but will noise be a huge issue or will image stacking also control noise.

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Long Exposure Noise Reduction takes a dark frame of the same duration to subtract the noise from the image. That's why there is a long delay; a 30-second exposure plus a 30-second dark frame plus processing time plus the time to write the image to the memory card. There will be obvious gaps in the star trails.

If the gaps are minor, they can be corrected in software like StarStax, for example. A 30-second shot followed by a 30-second plus gap is unlikely to be correctable. Even if you turn Long Exposure Noise Reduction off, there will be a tiny, probably correctable gap because of the time required to close the shutter, record the image to memory and then open the shutter for the next shot. In my experience, those are seamlessly correctable in software.

A technique commonly used in astrophotography is to take just one dark frame, with the lens cap on in the same conditions and exposure time, at the end of the shooting and then use dark-frame subtraction in Photoshop, Lightroom, GIMP and other software. Essentially, you are subtracting sensor noise from your image.

This also makes it easy to see the result with and without dark-frame subtraction.

  • I thought that you were supposed to do the subtraction before demosaicing. – JenSCDC Sep 6 '14 at 22:45
  • My assumption is that the relevant software performs the steps in the correct order. – chili555 Sep 8 '14 at 2:22

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