Strange fringing (?), colourful noise (blue, red, yellow) in contrasty footage

Started by PowerMac84, October 08, 2014, 11:00:42 PM

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PowerMac84

Dear ML fellows,

I have been to Canada for four weeks. Shot my documentary art film about forests there. Somebody talked me into ML and after reading I lot I gave it a try (7D, latest Nightly build from end of august by then) two days before leaving Europe. Honestly I was sceptical yet very interested in RAW shooting as we also own a Red. I love the Red workflow with Adobe Premiere.
Well so I shot some 20 128 GB cards in Canada and now I am trying to find which workflow is best for me before starting the serious editing process.
So far quite a lot clips look really strange. I have attached a link to one MLV that shows what I mean.
I shot almost everything in ISO 160 because I knew that ML tends to be a bit noisy. But so many trees look really bad. I do not now whether it is the hard contrasts of light and branches which produce fringing. Could somebody please take a look at that? Is that what some people mean by fringing? TO me it looks like some special sensor noise that could easily be removed during developing and de-bayering. Right?

So far I tried making ProRes files directly from MlRawViewer and also used the Resolve workflow to create ProRes files from the DNG (created either with RAW Magic and MlRawViewer).
Thanks a lot!

https://dl.dropboxusercontent.com/u/4902662/M14-0132.MLV


Patrick

Audionut

Might be worth extracting an DNG showing the issue, so people don't have to download 2.2Gb.
ML shoots raw at ISO multiples of 100, and does not tend to be a bit noisy.

http://en.wikipedia.org/wiki/Purple_fringing

Since the 7D line skips, the fringing is going to be line skipped also, which will probably lead to some funky appearance.  Try a better lens.


dmilligan

Looks like chromatic aberrations compounded by really bad aliasing, you'll get better results in crop mode, or scenes with not as much fine, high-contrast detail, or you can purchase an anti-aliasing filter (VAF). This scene is like a worst case scenario for aliasing and fringing.

Levas

Ah, the normal canon DSLR raw video artifacts (Common for cameras that use line-skipping for video, the 5dIII probably doesn't have this problem)
The pink ones is probably wrong white point used by the software, Blackmagic DaVinci resolve lite had this pink dots issue in older version, I believe since Davinci resolve lite 10 they solved it.
Looks like it's most pink stuff, so you maybe want to try out Blackmagic DaVinci resolve lite for video editing (It's free downloadable on their website)

The other colorful stuff(orange/green dots etc) is due to to line skipping in combination with debayering.
Most video editors don't let you choose what type of debayering is used, and most standard debayering is not made for line skipping sensor readout and gives artifacts like the ones you show.

However I found a workflow which get rid of most of these false color artifacts.
I use RawTherapee for mac(free, opensource) to develop the raw DNG's.
It let's you choose between different type of debayering/demosaicing options.
lmmse demosaicing seems to work best for lineskipping video.

Here's my workflow:
http://www.magiclantern.fm/forum/index.php?topic=3904.msg123338#msg123338

And here how to not let it crash on a mac when exporting a lot of dng's to TIFF
http://www.magiclantern.fm/forum/index.php?topic=12872.msg124224#msg124224



a1ex

These DNGs also look fine in ufraw (AHD + color smoothing enabled).

Levas

A1ex, you know this better then I do, can you confirm that the pink/purple stuff is due to wrong white point value used by the software ?

Levas

I already downloaded the MLV before you posted the DNG's.
So I took the liberty of trying out the workflow I described in the links I posted.
Made a 10 second MP4 of it with Quicktime 7 and uploaded it:

https://drive.google.com/folderview?id=0B1BxGc3dfMDaakVzUG51LS1GVkE&usp=sharing


Also put a tiff in the folder, to show how sharp/detailed they are.


a1ex

Quote from: Levas on October 09, 2014, 02:23:28 PM
A1ex, you know this better then I do, can you confirm that the pink/purple stuff is due to wrong white point value used by the software ?

No. If the white level assumed by the software is too high, you get pink highlights (large areas, not just isolated pixels). If it's too low, useful detail will get clipped to white.

In the DNG I've checked (last one), there are only 12 pixels above white level.

In this case, it seems to be aliasing + a weak debayer algorithm.

Levas


baldand

If you are converting in MlRawViewer with the stripe correction enabled (X in the stripe icon), try converting again with it off. This can be a side effect of the hot pixel detection I'd you are in a tripod and scene content is quite static.

PowerMac84

Thank you. Will read through the postings and try the workflows. Will keep you informed!

PowerMac84

I think I gave up. I've spent the last week trying to get this working. Ufraw I cannot get to work, maybe because I use OS X Yosemite and there is no standalone binary apart from GIMP which will not open DNG files. RawTherapee also does not even start. If I was a programmer... I would compile them. But then I have like 1000 MLV clips that would have to be batch processed...

The last workflow I tried was Adobe Camera Raw (CS 2014.1). With the AE workflow script (via VisionLog to ProRes 4444) it worked quite well. In ACR there's an option to remove Remove Chromatic Abberations and purple and green fringing. That removed some parts of that colourful noise in high contrast situation where leafs and the sky meet for example. In the end there is still a million of small green and red noise dots that make the footage unusable when in motion. Also there is normal noise that's layered.
Here is a MP4 of that file: https://www.dropbox.com/s/eehf95eqqfgeopx/Sequence%2001.mp4?dl=0
Please go through it frame by frame.

Thanks a lot,

Patrick Alan