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Artifacts after SNS HDR

PostPosted: Mon Aug 13, 2012 1:11 pm
by markdfink
I combined three exposures and was surprised by the artifacts I saw in the resulting image. This isn't noise, but artifacts, at least as far as I can see. I've attached the three images along with the blended one so you can see. I also attached the prs preset file. These are 100% crops of just part of the image. Is this a result of over zealous settings on my part? How do I fix this?

Just now, I did a quick test with the three attached source images and my prs file, and see the same results in the sky. If I choose some of the other default presets, I get varied results. Some have none of these artifacts while others show the same effect. So, I think I've answered my own question partially - it is the settings that I'm using. Still, how do I get the dramatic sky that I want and avoid these artifacts?

Thanks,

Mark

Re: Artifacts after SNS HDR

PostPosted: Tue Aug 14, 2012 5:13 pm
by markdfink
I've done some more testing, and it turned out to be the microdetails that was causing this. I had to reduce that setting to -77 to make these artifacts go away, but then that negatively affected the rest of the image. That's when I discovered and learned about masking. What a great feature! It allowed me to mask out the sky and apply a separate set of microdetail settings to just the sky. Unfortunately, you can't batch apply a preset that has masking, at least not as far as I could see.

Still, I'm trying to figure out why such significant artifacts were generated in the first place. Any ideas?

Mark

Re: Artifacts after SNS HDR

PostPosted: Wed Aug 15, 2012 2:28 pm
by den
I am not an expert at this... ...but if AHD interpolation quality is being used during RAW conversion, it can produce 'maze-like' artifacts that can become visible and objectionable in large, low tone/color contrast image areas such as 'skies/clouds' when using SNS-HDR tone-mapping, particularly with a "Dramatic" pre-set. Incidently, this is true for any image editor where these types of image areas are aggressively edited to increase their tone/color contrasts.

If you are using SNS-HDR as the image file RAW converter, then you could use its "n1 thru n9" RAW Noise Reduction option... ...this will be universally applied and soften overall detail. [Ref:http://www.sns-hdr.com/forum/viewtopic.php?f=7&t=352]

If you are familar with DCoffin's "dcraw.exe", another possibility is to specify a "-f" option, i.e., interpolation with RGGB as four colors.

Yet another possibility in addition and/or instead of using masks... ...is to reduce Microdetails and Microcontrast for a specific tone/color range without changing tones/colors outside the selected range as illlustrated:
capture_15082012_053848-1-1.jpg
capture_15082012_053848-1-1.jpg (75.16 KiB) Viewed 7408 times

...and sometimes, I will just make two or more SNS-HDR image versions with differing presets and preferentially composite blend image areas using an external editor and noise reduction...

Re: Artifacts after SNS HDR

PostPosted: Wed Aug 15, 2012 2:42 pm
by markdfink
Den, thanks for the reply. I'm using Lightroom and controlling noise there when converting to TIFF. I have no idea if AND interpolation is used in that process. I REALLY like the idea of excluding via tones/colors rather than a mask, since I could then batch process images. I'll have to test that out!

Mark