Latest post Mon, Nov 24 2008 11:46 PM by chuckkahn. 6 replies.
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  • Tue, Nov 18 2008 3:37 PM

    • chuckkahn
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    Can file import look as good as SD SDI capture?

    Can file import look as good as SD SDI capture?

    How many applications can make 601 compatible files for Avid's "601 color level" import?  I've seen  After Effects mentioned here -- are there others?   Is 601 file compatibility a video standard or just an Avid one?

    From what I can gather reading the manuals and these forums, for 8-bit video, 601 color level import is preferrable to RGB color level import because RGB import resamples the 1-255 levels to 16-235 (255 steps down to 219) -- that shouldn't look as good as 601, should it?

    Any clarifications or links for further reading would be helpful.   Thanks!

     

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  • Tue, Nov 18 2008 4:21 PM In reply to

    • BLKDOG
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    Re: Can file import look as good as SD SDI capture?

    To answer your question, yes file import can look just as good, if not better, than tape capture. It all depends on the origins of the file and the source material. RGB and 601 are simply color space choices, they don't necessarily imply improved resolution. Perhaps if you tell us the workflow you are considering we could be of more help.

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  • Tue, Nov 18 2008 4:48 PM In reply to

    • chuckkahn
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    Re: Can file import look as good as SD SDI capture?

    BLKDOG:

    RGB and 601 are simply color space choices, they don't necessarily imply improved resolution.


    But doesn't the RGB import process affect resolution?  As I understand it (for 8-bit NTSC video), the two import options come down to this:

    - RGB -- 1-255 is mapped to 16-235 -- thus a resampling of the 8-bit values would be performed, turning 255 RGB values into 219 "safe video" values.   That sounds like it would have an impact on resolution.

    - 601 -- 1-255 goes in as 1-255 -- and hopefully the source file respects superblack (1-15) and superwhite values (236-255).

    This is what I've gathered from the manuals and the forum.   If this isn't the case, then I would like to know.

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  • Tue, Nov 18 2008 4:55 PM In reply to

    Re: Can file import look as good as SD SDI capture?

    chuckkahn:

    - RGB -- 1-255 is mapped to 16-235 -- thus a resampling of the 8-bit values would be performed, turning 255 RGB values into 219 "safe video" values.   That sounds like it would have an impact on resolution.

    - 601 -- 1-255 goes in as 1-255 -- and hopefully the source file respects superblack (1-15) and superwhite values (236-255).

    This is what I've gathered from the manuals and the forum.   If this isn't the case, then I would like to know.

    Firstly, the RGB values extend from 0 - 255 (256 levels for 8-bit) and upon import are remapped to a 16-235 safe range (if RGB is set as the import colour space). If 601 is set, then a straight 0-255 mapping is employed.

    Resolution is often referred to as the frame size, or the actual pixel count. The width and height of a frame of video/film. 1920x1080 for instance, is certainly what I'd call a resolution (and I'm sure others would too).

    Altering colour levels won't affect resolution in the traditional definition of the term 'resolution', but it will affect the colour values across the range.

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  • Tue, Nov 18 2008 5:03 PM In reply to

    • chuckkahn
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    Re: Can file import look as good as SD SDI capture?

    malefunktion:

     

    Firstly, the RGB values extend from 0 - 255 (256 levels for 8-bit) and upon import are remapped to a 16-235 safe range (if RGB is set as the import colour space). If 601 is set, then a straight 0-255 mapping is employed.

    Resolution is often referred to as the frame size, or the actual pixel count. The width and height of a frame of video/film. 1920x1080 for instance, is certainly what I'd call a resolution (and I'm sure others would too).

    Altering colour levels won't affect resolution in the traditional definition of the term 'resolution', but it will affect the colour values across the range.


    Okay, so resolution is pixel count, so what is the term we use for when the "gradations" of each pixel are shifted from a 0-255 range to a 16-235 range?   A reduction of some sort has taken place.   Is it "gradalution"?

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  • Tue, Nov 18 2008 5:11 PM In reply to

    Re: Can file import look as good as SD SDI capture?

    Well when converting colours, depending on the use of 8-bit, 10-bit or in some packages logarithmic exponential processing - colour gradiation can occur whereby you can experience "banding" due to the restricted number of possible RGB values imposed by a limited bit count.

    For this reason, MC offers in most cases both 8-bit and 10-bit processing to help eliminate or minimise issues with 'banding' and poor 'gradiation'.

    When a pixel's colour value is altered, it is simply altered. This process is usually just called colour space conversion. (Not to be confused with colour sampling which relates to how pixels are recorded through a digital medium: Values like 4:2:0, 4:1:1, 4:2:2, 4:4:4 are all examples of colour sampling methods.)

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  • Mon, Nov 24 2008 11:46 PM In reply to

    • chuckkahn
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    Re: Can file import look as good as SD SDI capture?

    Here's a colorspace oddity:  Why do smpte bars exported with the same 601 export settings to Quicktime DV look different (darker) than bars expored to Quicktime Uncompressed or Quicktime Prores (lighter)?   Then all import back into the Avid with the same levels.   Does DV codec have some hidden video information?

    smpte bars in quicktime exports darker lighter

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