So - I'm beginning to rewrite notes for my students and I get to Linking (AMA as was). I am on MC 8.4 on Mac OS 10.10.3. There is quite a bit to this so be patient . . .
I started by looking at linking still graphics to avoid the Import process. Frameflex lets us adjust the image aspect ratio using Source Settings but what about the colour levels? Seems to work OK with full range (0-255) but I set up a test still graphic with video levels (16-235, 8-bit). I could not understand what the Source Settings were showing me so I decided to test with QuickTime exports from After Effects (a simple file with bars and grayscale). For those who have not investigated this, the Source Setting Color Encoding tab has a panel at the top which shows the (guessed) source color space and a menu at the bottom from which to choose a color transformation. Looks like the source color space interpretations are not always accurate.
1) 0-255 file (Full Range):
If the file was 0-255 (full range), rendered using the Animation codec, Source Settings reported it correctly as 'Full range'. A 'levels scaling (full range to video levels)' transformation setting was automatically applied from the Color Management setting and the histogram displayed as video levels. This seems to be correct. Color Management settings were 'Insert color transformations automatically' (the default).
If this 0-255 file was rendered out sing Apple ProRes 422 or 4444 or H264, Source Settings reported it as as Rec709 (video levels) (which it isn't!) but the histogram displayed it as video levels with NO transformation added. This is not what I would expect.
2) 16-235 file (Video levels)
In After Effects I applied a global level adjustment so that the file exported as 16-235 (also tested with clips that were 16-235 with no level change). When rendered out from AE with the Animation codec, it was reported as [Full Range] which it wasn't and the histogram showed it to be interpreted incorrectly. A 'levels scaling (full range to video levels)' transformation setting was applied automatically from the Color Management settings. if 'Insert color transformations automatically' is set, this leads to the blacks being raised and whites lowered - levels approx 30-219). This is clearly wrong. Deleting this colour transformation reset the levels correctly in the histogram so the file can be used but we should not need to do this.
Rendering out this 16-235 file using Apple ProRes 442 or 4444 or H264 from AE resulted in the file being reported as Rec709 (video levels) which it IS but the histogram shows it to be interpreted incorrectly (the blacks are raised and whites are lowered - levels approx 30-219) even though no transformation is seen to be added. This is clearly wrong. This can be fixed by adding the Color Transformation 'Levels Scaling: Video Levels to Full Range" which seems very counter-intuitive and back-to-front. This brings blacks to 16 and whites to 235 so the file can be used. It looks like the file is being interpreted as 0-255 even though reported as Rec709.
I started by looking at linking still graphics to avoid the Import process. Frameflex lets us adjust the image aspect ratio using Source Settings but what about the colour levels? Seems to work OK with full range (0-255) but I set up a test still graphic with video levels (16-235, 8-bit). I could not understand what the Source Settings were showing me so I decided to test with QuickTime exports from After Effects (a simple file with bars and grayscale). For those who have not investigated this, the Source Setting Color Encoding tab has a panel at the top which shows the (guessed) source color space and a menu at the bottom from which to choose a color transformation. Looks like the source color space interpretations are not always accurate.
1) 0-255 file (Full Range):
If the file was 0-255 (full range), rendered using the Animation codec, Source Settings reported it correctly as 'Full range'. A 'levels scaling (full range to video levels)' transformation setting was automatically applied from the Color Management setting and the histogram displayed as video levels. This seems to be correct. Color Management settings were 'Insert color transformations automatically' (the default).
If this 0-255 file was rendered out sing Apple ProRes 422 or 4444 or H264, Source Settings reported it as as Rec709 (video levels) (which it isn't!) but the histogram displayed it as video levels with NO transformation added. This is not what I would expect.
2) 16-235 file (Video levels)
In After Effects I applied a global level adjustment so that the file exported as 16-235 (also tested with clips that were 16-235 with no level change). When rendered out from AE with the Animation codec, it was reported as [Full Range] which it wasn't and the histogram showed it to be interpreted incorrectly. A 'levels scaling (full range to video levels)' transformation setting was applied automatically from the Color Management settings. if 'Insert color transformations automatically' is set, this leads to the blacks being raised and whites lowered - levels approx 30-219). This is clearly wrong. Deleting this colour transformation reset the levels correctly in the histogram so the file can be used but we should not need to do this.
Rendering out this 16-235 file using Apple ProRes 442 or 4444 or H264 from AE resulted in the file being reported as Rec709 (video levels) which it IS but the histogram shows it to be interpreted incorrectly (the blacks are raised and whites are lowered - levels approx 30-219) even though no transformation is seen to be added. This is clearly wrong. This can be fixed by adding the Color Transformation 'Levels Scaling: Video Levels to Full Range" which seems very counter-intuitive and back-to-front. This brings blacks to 16 and whites to 235 so the file can be used. It looks like the file is being interpreted as 0-255 even though reported as Rec709.
Rendering out from AE with an Avid DNxHD codec with levels set to 709 results in a file that is interpreted correctly in Media Composer (reported as 'Video Levels'). So why don't I/we always use this route? We need to be handle anything that comes our way.
According to the Avid documentation (which BTW, is not in the regular editing guide but in the high res workflow guide), we should be able to choose 'Unknown' as source color space and this should leave the file as it is. Choosing 'Unknown' has no effect.
The fact that the interpretation is inconsistent is one thing but it would be handy if we could TELL the system how to interpret the files as we can when importing. Anyone throw light on this? It seems that linking to genuine video (as in 'it came from a camera') is good but with generated graphic files that are not full range, I see problems.
The fact that the interpretation is inconsistent is one thing but it would be handy if we could TELL the system how to interpret the files as we can when importing. Anyone throw light on this? It seems that linking to genuine video (as in 'it came from a camera') is good but with generated graphic files that are not full range, I see problems.
With Best Wishes,
Roger Shufflebottom
+44 7973 543 660
Roger Shufflebottom
+44 7973 543 660
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Posted by: Roger Shufflebottom <rogershuff@yahoo.co.uk>
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this is the Avid-L2
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