Artifacts after SNS HDR

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Artifacts after SNS HDR

Postby markdfink » Mon Aug 13, 2012 1:11 pm

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
Attachments
Rousillon - France.prs
SNS HDR preset used to merge these images.
(2.9 KiB) Downloaded 311 times
light.jpg
light.jpg (37.16 KiB) Viewed 3563 times
medium.jpg
medium.jpg (61.33 KiB) Viewed 3563 times
dark.jpg
dark.jpg (50.19 KiB) Viewed 3563 times
SNSHDR.jpg
SNSHDR.jpg (139.41 KiB) Viewed 3563 times
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markdfink
 
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Re: Artifacts after SNS HDR

Postby markdfink » Tue Aug 14, 2012 5:13 pm

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
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Re: Artifacts after SNS HDR

Postby den » Wed Aug 15, 2012 2:28 pm

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 3536 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...
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Re: Artifacts after SNS HDR

Postby markdfink » Wed Aug 15, 2012 2:42 pm

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
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