Ursa RAW 4:1 - Bright Vertical lines that are not FPN

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Emilian Dechev

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Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostSat Jan 27, 2018 10:54 pm

I shot RAW 4:1 at 4.6K. All seemed good until I uploaded the files in Davinci. The footage had a very odd issue. Vertical lines, that are not FPN.

These are bright vertical lines, that can be seen in the brightly exposed areas of the sky, after applying a contrast curve.

DNG is provided below.

I checked project settings in Davinci, to go as "full resolution decoding" and being sure the timeline and delivery format is also 4608x2592

I will do another test tomorrow, comparing the UM 4.6K with the UM Pro.

Any info on the matter will be appreciated.

Update:

as stated by a Blackmagic rep, this issue happens because of the RAW 4:1 compression, but only on rare occasions under a heavy contrast curve.

Case closed.
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Last edited by Emilian Dechev on Tue Jan 30, 2018 11:25 pm, edited 5 times in total.
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Emilian Dechev

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSat Jan 27, 2018 11:02 pm

Here is a DNG.

The vertical lines can be seen after applying a contrast curve.

http://www.newactorsstudio.com/storage/ ... 000010.dng
Last edited by Emilian Dechev on Tue Jan 30, 2018 11:21 pm, edited 1 time in total.
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John Simpson

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 8:31 am

Emilian I downloaded your RAW

IMHO there's no issue here except no noise reduction and over sharpening... Set your Spatial Threshold to Luma: 2 Chroma: 10 and don't set your sharpening radius less than .47 (.48 optimal)... Problem solved!
JJ Simpson
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John Brawley

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 2:08 pm

Seems to me that the vertical lines are maybe viewer related ? I'm not seeing them here. Have you tried rendering a frame and seeing if they are still there ?

The "dancing pixels" sounds and looks like aliasing from the BMD camera not having an OLPF. This is the kind of situation that looks like this. Very fine moving detail on a high contrast background.

jb

https://www.flickr.com/gp/johnbrawley/023fhr
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Emilian Dechev

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 4:10 pm

Thanks for the advice, the sharpening is at default value. Need to do more testing.

Yes I rendered to 12-bit DNxHR and the lines are there.

John, in order to see the vertical lines, please use a color convrrtion to rec709, or just brighten thr image with a curve.

Will try to replicate it again with and without the internal ND, just to be sure.
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John Brawley

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 4:14 pm

Emilian Dechev wrote:Yes I rendered to 12-bit DNxHR and the lines are there.

John, in order to see the vertical lines, please use a color convrrtion to rec709, or just brighten thr image with a curve.

Will try to replicate it again with and without the internal ND, just to be sure.



I'm not seeing it ? Heres a REC 709 and the curve lifted ?

https://www.flickr.com/gp/johnbrawley/318j33

JB
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Emilian Dechev

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 6:07 pm

Hi John, sorry to mis-leading you. Its not visible in a bright sky, like in your example.

Please try again, without going to REC709, just use a contrast curve like that:

http://www.newactorsstudio.com/storage/umpro_raw.png

If you still dont see it, then it must be some display setting in Davinci.
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John Brawley

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 6:14 pm

Emilian Dechev wrote:Hi John, sorry to mis-leading you. Its not visible in a bright sky, like in your example.

Please try again, without going to REC709, just use a contrast curve like that:

http://www.newactorsstudio.com/storage/umpro_raw.png

If you still dont see it, then it must be some display setting in Davinci.


Yeah I'm not seeing it. Here's your curve both with and without a straight 709 transform.

https://www.flickr.com/gp/johnbrawley/KD0bV4

https://www.flickr.com/gp/johnbrawley/514p98

I'd also say, that curve is a pretty extreme grade...

JB
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Emilian Dechev

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 6:30 pm

Alright John, thanks for the feedback! So it is some kind of a display issue.

Will try to find anything related to "quality" inside Davinci.
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thomas bruegger

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 8:29 pm

Emilian

I see it too. when boosting up the contrast and bring the sky down there is some strangeness. its also visible in BM-Film Colour and Gamma.
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Emilian Dechev

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Re: RAW 4:1 - JPEG compression and Vertical lines?

PostSun Jan 28, 2018 9:20 pm

Wow alright so I am worried again...

Could not find any "quality" settings in Davinci, aside from Project / timeline resolution and "Full" decoding, which is on by default.

I didnt have time to do more tests today, but tomorrow I will surely compare the UM Pro with the UM46 and also RAW 4:1 vs RAW Full.

Here is the whole sequence from the 1st test, if its worth looking at:

http://www.newactorsstudio.com/storage/ ... 2_C005.rar
Last edited by Emilian Dechev on Mon Jan 29, 2018 9:25 pm, edited 1 time in total.
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Emilian Dechev

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Re: UM Pro - Bright Vertical lines that are not FPN

PostMon Jan 29, 2018 10:55 am

Alright guys, so I did test both cameras in both settings:

Ursa Pro in RAW and RAW 4:1

Ursa 4.6K in RAW and RAW 4:1

I shot the same bright scene with blue sky. I cannot see the vertical lines in any of the files.

I cannot reproduce the problem.

So I am back at square one. Maybe it was a 1 time event, that the UM Pro sensor was a bit off.
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thomas bruegger

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Re: UM Pro - Bright Vertical lines that are not FPN

PostMon Jan 29, 2018 12:13 pm

To me this looks like a compression issue, the trees will stress any codec. did you do the new test also with content that goes hard on the compression like trees, grass or floating water with lots of waves. Although its RAW and its only 4:1 it should not produce fragments like this. What was the f-stop on the original shot?

maybe its a one time issue and something in the camera did not boot correctly.... things happen....
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Emilian Dechev

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Re: UM Pro - Bright Vertical lines that are not FPN

PostMon Jan 29, 2018 1:39 pm

Yes - the same scene as before.

The compression artifacts show up only after a very strong contrast curve, which I guess may be expected even in RAW. Even in full RAW as well as 4:1.

I cannot see the vertical lines now.

Here are the files from the 2nd test:

http://www.newactorsstudio.com/storage/ ... D_test.rar
Last edited by Emilian Dechev on Tue Jan 30, 2018 9:05 pm, edited 1 time in total.
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thomas bruegger

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Re: UM Pro - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 5:27 pm

just examined the second test you did. the stripes only show up in the 4:1 compressed image i cant see it in the full raw. so it is a a compression issue.
just out of curiosity i compressed the full-raw with slimraw in 4:1 and 7:1 Compression. the 4:1 looks pretty o.k. the 7:1 is similar compressed as the 4:1 out of the camera. but its clear they could improve the incamera raw compression a lot!
here are the slimraw compressed dng's
https://drive.google.com/file/d/1fFdqNP ... sp=sharing
Thomas Bruegger / garage5 GmbH
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Emilian Dechev

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 9:13 pm

Hi Thom, thanks for the reply.

I still cannot see the stripes on the second test.

But they are really visible on the 1st test.

As far as I know, the nature of the "compressed raw" is about the same, as in a ZIP archive? That should be "lossless", just taking more time to de-compress. Or am I wrong?
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CaptainHook

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 10:33 pm

Raw 3:1 and 4:1 are "visually lossless", but can potentially show artefacts when "stressed" in post processing and scene complexity like you've seen/done here. There is the lossless option in camera if you would prefer but comes at the expense of much larger file sizes/data rate.
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Emilian Dechev

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 10:35 pm

Thanks for the info, mr. Captain!

Can you advise on these bright stripes, could they be provoked by the 4:1 compression? I could not see them in full RAW for sure.
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CaptainHook

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 10:51 pm

Yes I've seen these before as a result of 4:1 compression - but only on a fairly complex scene and then changing exposure in post and applying strong processing. In fact I was explicitly trying to find artefacts for development reasons, but otherwise in typical shooting and pushing the image as far as I normally would in post it hasn't been an issue for me at all.

As always I would recommend testing the various options in the conditions you will shoot in and decide the best option for you.
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Emilian Dechev

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostTue Jan 30, 2018 11:23 pm

Alright Captain, thanks for clarifying the matter!

For development purposes, here is the DNG for testing.

http://www.newactorsstudio.com/storage/ ... 000010.dng
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thomas bruegger

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostWed Jan 31, 2018 6:38 am

thanks Captain Hook for clearing up the matter.

Is there a way and a will to imporove the internal compression quality? the uncompressed dng that i compressed to 4:1 with slimraw does not show any of those artifacts.
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Dmitry Shijan

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Re: Ursa RAW 4:1 - Bright Vertical lines that are not FPN

PostThu Feb 01, 2018 3:56 am

This looks like Cross Hatching effect. It can be fixed. There is a thread about solutions for this problem viewtopic.php?f=2&t=51936&start=500

1. Wrong debayering of second green pixel produces semy-invisible fixed pixel grid which is partially hidden under the sensor noise. As a result at some zoom or scale levels in various players and apps this invisible grid may produce highly visible cross-hatch moire-like pattern.
2. Depending of image contrast, added sharpen and noise reduction amount, and player scaling method this pattern may be visible or not visible at all.
3. In BMMCC which is limited to 1920x1080 resolution this makes sensor Noise and FPN more visible (it behaves like some kind of shadow noise and FPN sharpening, adds additional digital artifacts to noise texture) and this limits the amount of visually usable shadow details.
4. People noticed this effect in BMPCC, BMMCC and BMPC, UM4.6K cameras. In BMPCC it is harder to see because it is slightly noisier than BMMCC and pixel pattern more hidden under the noise.
5. This effect depends of camera firmware version.
6. This problem can be fixed with fix in CornerFix app https://sites.google.com/site/cornerfix ... patterns-1 with applying a BayerGreenSplit500.cpf settings. This fix works only in ACR. All other RAW processing apps ignores it.
7. BM support team answer: "this is currently under investigation by our Development team"
8. BM team RMA few cameras but results are random and not perfect.
9. As a solution for this problem shifting image position by setting X Y position to 0.5 works very well (note that in Resolve this works only with RAW footage, but in Adobe apps it works with both ProRes and RAW footage)
UPDATE: In Resolve, simply use the "pan/tilt" setting in the Color Tab (same values of 0.5 each), instead of "xy position" in the inspector. Should work for ProRes-Footage as well ...
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