How can I reduce severe color noise in comet photos from a Micro Four Thirds camera?
Asked 7/20/2020
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I photographed Comet C/2020 F3 at 175mm on a Micro Four Thirds camera using ISO 6400, f/5.6, and 2-second exposures. I planned to reduce noise by stacking about 25 frames, but only 6 were sharp enough to use. After stacking in Sequator, the result still showed very strong color noise, and Lightroom/Photoshop noise reduction had little effect, especially after adjusting black and white points. How can I reduce this kind of noise in processing, and what should I change when shooting again to get a cleaner result?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
5y ago
2 Answers
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Apparently, this is an issue with sequator. I tried stacking the images with DeepSky Stacker, and the result is a lot better:
100% view from LR, Exposure +2EV (Sequator used an auto exposure function which seems to lack in DSS - or, more likely, I just did not see it as I only tried the programm for about an hour - so the image came out a lot darker. It is still very noisy (but consider, I had only 6 images from a MFT camera at its highest ISO), but it can be reduced at least:
The same image with color and luminance NR both at 50.
I am not sure why DSS has better results here. I assume that Sequator had troubles with detecting the noise in the images and produced a stack result that still was very noisy. I also have to mention that the Noise in the Raw images was the most extreme that I have ever seen - this includes ISO 25600 at my Beginner APS-C DSLR.
This is by no means a "bashing" of Sequator. I find the programm to be somewhat more intuitive than DSS and I have used it with great results. Another practical feature is that it can automatically freeze the foreground.
Originally by user91372. Source · Licensed CC BY-SA 4.0
user91372
5y ago
0
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The main problem is very low signal-to-noise ratio, with some motion blur/shake mixed in. If the source frames are extremely noisy, software noise reduction can only do so much.
From the answers, the most effective fix was to stack with DeepSkyStacker instead of Sequator; in this case DSS produced a much cleaner result and the remaining noise could then be reduced normally in Lightroom.
For a reshoot, the best improvement is to capture more usable frames and make each frame cleaner:
- use a remote release or otherwise avoid touching the camera
- keep the camera steadier so more frames are sharp enough to stack
- try lower ISO and longer exposures, balancing against star trailing at your focal length
- shoot multiple test combinations rather than relying on one setting
Stacking many frames is the practical solution here; with only 6 noisy ISO 6400 frames from a MFT camera, expect limited recovery. If possible, gather substantially more sharp exposures. In short: use better stacking software, improve frame stability, and prioritize more clean frames over aggressive single-image noise reduction.
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