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b/w artefacts after converting
Hi all,
im having a problem i could need some help with.
im currently working on a film noir like project (high contrast & black&white).
ive filmed a shot of a woman smoking with a light source on the left side. when i convert this to b/w i get some “artefacts” that look like jpg artefacts in photoshop.
actually ive had this problem in photoshop before and could solve it by working in 64 bit mode – cause then more different shades of gray are available (or something like that).but how do i handle this problem with video?
ive tried putting a gause on the clip but the effect gets even more ugly (same with magic bullet denoiser).
the clilps are filmed with a canon 7d so there is quite a bit of noise.
im not sure if you can see the jpgartefactlike problem in this picture – it shows better in video and full res.
I really hope someone can help me cause ive tried a lot of things and nothing really worked.
a possible solution could be using a different codec but here i have the problem that i want to work in 1280×544.
working with DNxHD in 64bit solved my artefact problem but when i tried to play the exported file it wasnt 544 but 720 (stretched the video). which obviously is even more ugly than the artefacts.well ive been thinking in different directions but till now nothing worked.
everything is appreciated – thanks for the help guys.cheers
danielll
Link:
0_geli.jpg -
3 Replies
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really no one knows about that? 🙁
or how to get rid of the artefacts 🙁 -
Looks like banding. Your source footage was recorded using 4:2:0 Y’CbCr (YCC) color with 220 graduations (16-235). When shown on an 8-bit display the signal is converted to 4:4:4 RGB with 256 graduations (0-255). The combination of chroma sub-sampling and 8-bit rescaling leaves gaps in the color spectrum. Take a look at the image through the RGB Parade scope and check for black horizontal lines. The missing colors correlate to the bands in the RGB image.
There are a few ways to manage your workflow to minimize the issue, but it will be difficult to overcome if the delivery codec is 8-bit 4:2:0 YCC (e.g. H.264, MPEG-2, VC-1, Flash). The best bet is to add some grain with the Noise effect; about 1.5-2.0% should work.
To avoid having noise appear on the actor make a copy of the clip and place it on the timeline above the original clip. Add a Luma, Chroma, Color, or RGB Difference Key (whichever one works best with the footage) on the top clip to separate the background from the actor. Add noise to the bottom clip.
Regarding the codec, if you want to use DNxHD then edit the footage and create intermediate files with a 1280×720 sequence. When it is time to deliver the final file, just embed the 1280×720 timeline into a 1280×544 sequence and export at 1280×544.
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i forgot to answer, sorry. the grain did it.
thanks a lot!
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