[dosdan]

Since it's very easy these days to do a burst of photos, I'm interested in images where you've used photo stacking of the same exposure (not HDR/blended exposure bracketing) to get better noise performance. Theoretically, 8 photos = 3 stops noise improvement (2^3 = 8). So 8 shots at ISO 100 = 1 shot at ISO 12.5

Please post your stacked shots, provide exposure info, whether it was hand-held or on-tripod, and mention what stacking software and any other PP techniques you've used.

Perhaps a small 100% crop from one of the stack images & the stacked result, with the same tone curve or exposure boost applied to both to keep the comparison valid, would be interesting too.

Here's my simple test, but I'd like to see some real shots, rather than test shots:

https://www.pentaxforums.com/forums/post-processing-printing-software-darkroo...king-test.html


I know this stuff's done a lot in celestial photography, but I like to see some terrestrial examples.


Dan.

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Last edited by dosdan; 01-17-2010 at 12:32 AM.

Moved to Post Processing.

[interested_observer]

Morning Dan, I did not really know what to expect when I clicked on the thread - but to me it has become very interesting. I have been using ISO 100 for the overall quality and the low noise, especially in stitching. However, upon stitching the results, I think (maybe its my imagination or aging eyes), but in some cases my stitched results seem to acquire noise. This may be a way around that, or to just boost the image quality. Something else to try.

One question, it appears from the documentation that the utility, requires separate images, as opposed to n number of copies of the same photo. Have you found out anything with respect to replicating the same photo in order to reduce noise and boost resolution.

I really did not think of this approach, however we used it extensively for GPS positions, especially early when not all the satellites were up, in order to improve the positions accuracy.

[dosdan]

One question, it appears from the documentation that the utility, requires separate images, as opposed to n number of copies of the same photo. Have you found out anything with respect to replicating the same photo in order to reduce noise and boost resolution.

The stacked images are of the same things, but they can not be duplicated from just one image. The idea is that the noise is truly random (unless you have some thermal sensor issue that causes the same defect noise, a "hot" pixel, to appear in the same location each time).

You then combine the images though averaging. Say a pixel produced by a very bright light in the subject was say 100% of FS (digital full scale) in each shot. You take 8 shots. After averaging, that's 8 x 100 / 8 = 100. Now take a random noise pixel that's at 2% FS in one of the shots. Being random, this may not be matched in the other 7 shots. So, after averaging, that's 1 x 2 /8 = 0.25, a NR of 8x.

Dan.

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Last edited by dosdan; 01-17-2010 at 01:08 PM.

[jbinpg]

Dan - All Pentax DSLRs from the K10D on have the capability to do multiple exposure with exposure averaging which I believe is what you are asking for. There are many examples of this mode of image on the internet including this site. Note that one difference between the in-camera stacking and that of astronomical stacking software is that there is no allowance for removing between-frame motion in-camera.

You can take up to 9 frames with EV averaging which works out to an equivalent ISO sensitivity of 11 and change.

Jack

[dosdan]

Dan - All Pentax DSLRs from the K10D on have the capability to do multiple exposure with exposure averaging which I believe is what you are asking for. There are many examples of this mode of image on the internet including this site. Note that one difference between the in-camera stacking and that of astronomical stacking software is that there is no allowance for removing between-frame motion in-camera.

You can take up to 9 frames with EV averaging which works out to an equivalent ISO sensitivity of 11 and change.

Jack, I prefer to do the stacking in software, because it is possible, even on a tripod, to get some vibration. PhotoAcute can do sub-pixel alignment (I presume sub-pixel is needed for super-resolution processing) and can correct hand-held. FDRTools is more limited, but can correct shots from a tripod.

Dan.