Does dithering reduce Bayer filter noise?
Posted 25 December 2013 - 12:48 PM
Posted 25 December 2013 - 12:58 PM
Posted 25 December 2013 - 01:12 PM
If properly debayered before combining, you should not need to dither and there should not be a debayer matrix visible.
Agree with Charlie; you might be wrongly referring to the pattern you see. Regards
Posted 25 December 2013 - 03:15 PM
Posted 25 December 2013 - 03:22 PM
That said, you mention "distinct bayer filter pattern noise" and that makes me wonder if you have some other issue, perhaps with your calibration frames or method of debayer. Can you post an example of this pattern noise?
Posted 25 December 2013 - 05:20 PM
Posted 25 December 2013 - 05:24 PM
You said you are capturing directly into Nebulosity/FITS - In the Nebulosity preffs under "Acquisition mode" are you set to "RAW Acquisition" or one of the two "Recon" types? It should be RAW type as "Recon" mode is actually JPEG image mode when Neb is controlling a DSLR.
Posted 25 December 2013 - 06:02 PM
Posted 25 December 2013 - 06:48 PM
Anyway, with it set to RAW mode you may find the mottle is reduced a bit further (and should definitely find an increase in the dynamic range out of the stacks).
Posted 25 December 2013 - 10:15 PM
Yes, I expect so. I was wondering why I wasn't able to stretch my images further, it didn't seem right compared to the RAW images I was taking before capturing with Nebulosity - now I know why. Again, thanks very much!
I'll also give the dithering a try to see how it affects the mottle. Now to hope for clear skies this weekend.
Posted 25 December 2013 - 11:02 PM
Nevertheless, dithering does help. But I have yet to experience a non-dithered stack! No matter how good the autoguiding, unless you are using a very short focal length, the stars span more than a single pixel and the atmosphere gives ample dither anyway. Nevertheless, when I did some rudimentary stellar spectroscopy I noticed noise from the Bayer array:
The middle strip is an undithered spectrum, in which noise is clearly visible, while the bottom is a vertically-integrated spectrum, sort of like a dithered spectrum.