Author Topic: Davinci color artefacts  (Read 8839 times)

vlasena

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Davinci color artefacts
« on: January 22, 2016, 11:48:45 PM »
Hello,

I am trying to accommodate workflow using Davinci Lite on my mac. However I can not get rid of the colour artefacts I am getting on the first screen "Media" when I am adding files or even previewing them. The issue is consistent for MLVFS as well as for MlRawViewer (if I export files to DNG).

I have tried using all default settings as well as settings explained in the workflow here "http://timeinpixels.com/2015/02/common-resolve-and-premiere-roundtrip-issues/" however nothings seems to help. Here is how it looks:


At the same time the same image opened in Photoshop or Lightroom does not have these issues:

baldavenger

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Re: Davinci color artefacts
« Reply #1 on: January 23, 2016, 02:31:53 AM »
What settings did you choose in MLVFS? Post a link to the original MLV (or just one of the dngs) and you'll get some feedback.
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hjfilmspeed

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Re: Davinci color artefacts
« Reply #2 on: January 23, 2016, 03:13:00 AM »
Do the artifacts show up after you render from resolve? I noticed that when you change the preview settings to I think bilinier it makes the preview better. Im wondering if its just the preview

DeafEyeJedi

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Re: Davinci color artefacts
« Reply #3 on: January 23, 2016, 05:49:56 AM »
Post an original copy of MLV and upload if you can...
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cmccullum

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Re: Davinci color artefacts
« Reply #4 on: January 23, 2016, 06:00:37 AM »
To my eyes, it seems that the artifacts are still present in the second image, but the second picture is brighter which makes them less apparent. Anyone else see that?

budafilms

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Re: Davinci color artefacts
« Reply #5 on: January 23, 2016, 07:59:24 AM »
The first image in Davinci is at 100% (corner up to the left) the other one no.

vlasena

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Re: Davinci color artefacts
« Reply #6 on: January 23, 2016, 12:24:03 PM »
Thanks everybody for a quick answer! Here are my last settings:


I have also tried with all settings set to off - result is the same.

For the reference this is the DNG file from MLVFS:
http://www.filedropper.com/m11-161412016-00-110001c0000000000

And this is a DNG file generated by MlRawViewer V 1.4.3:
http://www.filedropper.com/m11-1410000000

I agree that the DNG files does not seem to be perfect either, i can also observe small blurred areas, however the photoshop and lightroom seems to render these areas perfectly well. I am thinking maybe I should make some colour space adjustments in the davinci? I have tried a few things, but did not found the way around this problem..

Levas

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Re: Davinci color artefacts
« Reply #7 on: January 23, 2016, 01:57:04 PM »
Moving water is known for causing aliasing problems.
You can still see some artifacts in the lightroom example, but it's definately less.
Lightroom probably uses other debayering proces or does some chroma smoothing by default ?

But the example you show in Davinci resolve can be easily fixed I guess.
Try to change the colorspace on the node from RGB to LAB. (right mouse click on the node in the color menu)
Then disable channel 1 (also right mouse click on the node in the color menu)
After that use the blur slider and set it to 0.80 or higher if needed.

Or use the chroma shmooting option in MLVFS, this probably has the same result.

mothaibaphoto

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Re: Davinci color artefacts
« Reply #8 on: January 23, 2016, 02:21:32 PM »
It's "dead" or "cold" pixels.
Try this:

vlasena

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Re: Davinci color artefacts
« Reply #9 on: January 23, 2016, 05:30:01 PM »
Thanks everybody!!!! But so far nothing of these is working :(

0. the issue is both persistent in preview as well as after export to ProRes 422

1. i have tried changing colour space to lab -> scopes seems to show improved highlights, however the issue is not getting resolved with this

2. the technique to fix dead pixel explained in the video seems to be irrelevant for this case. In my case pixels are randomly jumping, so it is not one pixel, it is the whole sensor.

3. i have also tried ACES Color Space for the project settings, but the issue seems to stay. Here is manual on how to do it (i hope link works):

baldavenger

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Re: Davinci color artefacts
« Reply #10 on: January 23, 2016, 10:28:50 PM »
Try different MLVFS settings, such as everything off or none, and then try introducing chroma smoothing and upload the dngs. MLRawViewer should only be used for convenient viewing and not post production. Only after getting the least contaminated results should you proceed to using chroma smoothing in Resolve. I suggest selecting YUV in a node and un-ticking channel 1, then applying blur to the node. LAB can do funny things with the highlights sometimes, so YUV is safer.
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Levas

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Re: Davinci color artefacts
« Reply #11 on: January 24, 2016, 01:04:05 AM »
Just follow the whole procedure, not just one step ;D

"1. i have tried changing colour space to lab -> scopes seems to show improved highlights, however the issue is not getting resolved with this"

I also told you, after you change the color space to LAB, you need to disable channel 1.
After channel 1 is disabled you need to apply a blur of about 0.80.
And voila, blue, purple boxes are gone.

I downloaded your DNG with the sea in it, loaded it in DaVinci, went to the color tab, changed the colorspace to LAB, disabled channel 1, applied a blur of 0.80 and the blue and purple colors were gone.

This means it is aliasing, it's because your camera is lineskipping, it only reads every third line of your sensor.
Moving water and waves is high contrast detail, to get rid of artifacts, just apply a chroma blur 

mothaibaphoto

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Re: Davinci color artefacts
« Reply #12 on: January 24, 2016, 07:55:23 AM »
2. the technique to fix dead pixel explained in the video seems to be irrelevant for this case. In my case pixels are randomly jumping, so it is not one pixel, it is the whole sensor.
Sorry, i downloaded just one dng frame and it looks like cold pixels out of my MKII :) If that artifacts moving, this is definitely not cold/dead pixels. Moreover, if you shoot non-crop mode, you probably never see pixel level artifacts due to binning. But see aliasing. So follow Levas, or shoot on crop :)

Walter Schulz

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Re: Davinci color artefacts
« Reply #13 on: January 24, 2016, 08:15:14 AM »
5D2 does line skipping. 5D3 is the only ML enabled cam doing binning.

mothaibaphoto

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Re: Davinci color artefacts
« Reply #14 on: January 24, 2016, 08:26:42 AM »
And how to get FHD out of MKII just skipping lines?
Recent interesting thread on this.
This correct: Moreover, if you shoot non-crop mode, you probably never see pixel level artifacts due to column binning. But see aliasing due to line skipping.

vlasena

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Re: Davinci color artefacts
« Reply #15 on: January 24, 2016, 02:18:30 PM »
Thanks Levas for your tips. However I am not sure how to execute what you have explained. Once I add my CinemaDNG file to the library I apply the below settings:


After that I add it to the timeline and move to the colour. I tried to do everything on one node, the result is too blur. I also tried to have two nodes, but the result is also too blurred:
On the first node I change color space to LAB and also disable channel 1.
On the second node I add blurring of 0.8:

vlasena

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Re: Davinci color artefacts
« Reply #16 on: January 24, 2016, 02:24:19 PM »
Forgot to add, i have tried all combinations of settings for the MLVFS. The results seems to be the following:
Bad Pixel Fix - no impact on the image quality
Vertical Stripe Fix  - no impact
Chroma Smoothing - 3x3 and 5x5 makes the thinks looks even worse. The setting None vs 2x2 is subjective - some new artefacts in 2x2 may appear and some other may be gone.
Fix pattern noise - did not see the impact either.

So in the nutshell, MLVFS does not seem to help the situation.

Levas

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Re: Davinci color artefacts
« Reply #17 on: January 25, 2016, 12:01:31 AM »
I guess it didn't work because you changed colorspace to lab and disabled channel 1 on the first node and then applied the blur on the second node.

Doesn't matter which node you use, but you need to do it all on the same node
-colorspace lab
- right click on the node and get channel 1 deselected. (Channel 1 is the luma channel, if you deselect it, the blur is not done on the luma channel, this will let the image look sharp)
-use the blur slider, about 0.80

vlasena

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Re: Davinci color artefacts
« Reply #18 on: January 25, 2016, 11:06:50 PM »
Yes, it  worked!!!
Thanks a lot :)

Levas

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Re: Davinci color artefacts
« Reply #19 on: January 26, 2016, 12:14:37 AM »
Great :)