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Problem exporting still frame – color noise (vertical banding)
hey all,
been working in final cut for years (since version 2!) so i’m sort of well versed in many aspects of its use. i do however have a problem for which i can’t seem to find a solution.
currently using a sony nx5 and transcoding to prores on capture. no problems there. i develop for the web so my final output is always digital.
i keep everything yuv until final output which is typically h.264 – resizing scenes using uncompressed 8 bit 4:2:2 then send the uncompressed clips to squeeze for compression.
i must create a series of still frames as part of my workflow. naturally i do this by meticulously stepping through the sequence and hitting Shift+N when i want a still. I drag the still to a new bin then when then drag all the stills i created to a new timeline that matches the settings of the timeline that i took the stills from (again uncompressed 8 bit).
everything looks fine until i export the timeline as an image sequence using quicktime conversion. i export as image sequence and generally use png as the output format although i’ve tried psd and pict files with the same results.
the problem:
before the export to stills the images look fine. after export they all have a strange color distortion with vertical banding between contrasting colors. again, this effect is NOT there prior to export as still sequence and the colors look fine.
here’s the movie prior to exporting a still:
https://farm5.static.flickr.com/4062/…d486d8f4_o.jpg
^ (this is a screen grab of the actual movie playing in the quicktime player)
and a still image taken from the same frame of the movie using export as quicktime conversion (png):
https://farm5.static.flickr.com/4024/…ab63515b_o.jpg
note the lettering on his chest when you compare both images – there is a strong vertical banding surrounding the orange letters against the blue tshirt in the still image that is not present in the screen cap of the actual movie.
the same thing happens if i export the frame at the current playhead position as a still image using quicktime conversion. basically, anytime i export from final cut as a still (no matter the file format or technique used) i see the issue. even tried exporting image sequence using compressor.
i realize that 4:2:2 isn’t the best color space to work in but this vertical banding between contrasting colors is not present in the original movie – only in the still image that is exported from the original movie. there is no compression added to the still image, and i have tried all formats available.
anyone else experience this? have a workaround? i’ve been using final cut for a while but this kind of has me baffled!
thanks for your help!
karl
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4 Replies
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Karl,
The links to your examples are broken, but that’s okay, cuz I think I get the idea.
I believe that a slight change in your workflow might solve the problem for you.
Instead of your 8-bit uncompressed step, you change that part of the workflow to 10-bit uncompressed, that should avoid the banding. It’s also possible that ProRes could also solve the issue, as it is also a 10-bit codec.
Test those out and please let me know if that solves your problem.
David Roth Weiss
Director/Editor/Colorist
David Weiss Productions, Inc.
Los AngelesPOST-PRODUCTION WITHOUT THE USUAL INSANITY ™
EPK Colorist – UP IN THE AIR – nominated for six academy awards
A forum host of Creative COW’s Apple Final Cut Pro, Business & Marketing, Indie Film & Documentary, and Film History & Appreciations forums.
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thanks david, i’ll give that a try.
the problem with 10 bit uncompressed is that the files aren’t recognized by squeeze so i’ll have to find a workaround there. i’ll let you know how it works!
turns out the footage starts at pro-res but the problem isn’t introduced into the video when it’s output as 8 bit uncompressed. only when i export a still frame from that footage. hope we’re on the same page.
karl
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oh here’s the corrected images:
screen grab of actual video shown in quicktime player:
https://farm5.static.flickr.com/4062/4449760232_92d486d8f4_o.jpg
sill image output from that video (as seen above) using quicktime conversion in fcp:
https://farm5.static.flickr.com/4024/4448984567_9dab63515b_o.jpg
you can see the color banding i’m referring to around the lettering in the t-shirt in the second pic – not there in the actual movie. only in the still output.
karl -
I’m wondering if I need new eye glasses or a new screen, because I can’t see anything wrong with that image.
Can you be more specific about what you are seeing on your screen?
Do you perhaps have a 6-bit LCD? Those are very common, and then you may see stuff that others don’t see.
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