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Black bands on either side


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#1 Brian Drysdale

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Posted 31 August 2005 - 03:21 AM

The editor on a couple of short films that I shot using a SDX 900 shooting on DVPro50 at 25P has noticed narrow vertical black bands on either side of the 16 x 9 picture. He's cutting it on Final Cut Pro HD using interlaced PAL, rather than progressive frames and he's curious about these black bands. The pictures themselves are fine and the black bands are outside normal viewing on a monitor, but would be seen on underscan.

Has anyone come across these before and know the cause?
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#2 Phil Rhodes

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Posted 31 August 2005 - 06:00 AM

Hi,

Perfectly normal and no, it will not be seen on underscanned displays if they are operating correctly. I believe it's something like the first and last six pixels of each line which may contain picture but, according to the 601 spec, "may not be used for any other purpose". Most cameras blank them.

This is one reason that a lot of software, including Adobe Premiere, gets aspect ratio conversion very slightly wrong - the actual 4:3 or 16:9 picture area is that inside the 704-wide central area of the frame, not the entire 720 width.

Phil
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#3 Brian Drysdale

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Posted 31 August 2005 - 09:52 AM

Hi,

Perfectly normal and no, it will not be seen on underscanned displays if they are operating correctly. I believe it's something like the first and last six pixels of each line which may contain picture but, according to the 601 spec, "may not be used for any other purpose". Most cameras blank them.

This is one reason that a lot of software, including Adobe Premiere, gets aspect ratio conversion very slightly wrong - the actual 4:3 or 16:9 picture area is that inside the 704-wide central area of the frame, not the entire 720 width.

Phil

<{POST_SNAPBACK}>


Thanks, I've told him not to worry. Most productions here are shot on Sony cameras and they don't have the black bands on either side on the FCP.
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#4 MatthewG

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Posted 31 August 2005 - 03:37 PM

The real pain with the black bars is that if you compress for web or dvd and its shown on a computer monitor....those darn bars DO show. You need crop 5 to 10 pixels on the left and right on Compressor or whatever app you use for web and dvd compression to crop those out.
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#5 Brian Drysdale

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Posted 31 August 2005 - 04:31 PM

The real pain with the black bars is that if you compress for web or dvd and its shown on a computer monitor....those darn bars DO show.  You need crop 5 to 10 pixels on the left and right on Compressor or whatever app you use for web and dvd compression to crop those out.

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These films are being delivered on Digi Beta, but there will be dvd copies made and the films are also going be video projected at festivals.

I'll pass that info to the editor.
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