Black and white your TV won't like - Help!

5 replies [Last post]
Snake Plissken
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Joined: Sep 17 2000

I read somewhere that absolute values of black and white are outside the range most TVs like to deal with. In Premiere/Photoshop I frequently use the levels option to improve the contrast of certain shots etc. Premiere allows me to adjust the range between 0 and 255 for black and white, which maybe it shouldn't. What are the values I should keep black and white between? Does the broadcast colours effect counteract this?
Help appreciated.

Bob Barker Again
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Joined: Jul 30 2001

Snake I had the same problem!
Idont know what the values should be but recently I created a pure white screen in photoshop then pasted logos on it and took it into P6 when it played on tv wavey lines appeared across just that clip after many failed attempts at correcting it I put it back into photoshop and reduced the white to what looked like almost pale grey and when I played it from P6 and recorded it to tape it played perfectly. ( and strangely enough it looked white on tv. )
Bob.B

Snake Plissken
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Joined: Sep 17 2000

Thanks for the reply, Bob. That's it exactly. I've been reducing the white to a paler shade to make it work on TV. There's an NTSC colour filter in Premiere. I wonder if this would keep whites in the safe zones. Seems strange that Premiere doesn't display a warning to stop this from happening.

Alan Roberts at work
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Joined: May 6 1999

DV and D8 accord to the ITU Rec.601 spec. for digital video. In an 8-bit system, black is at level 16, white is at level 235. In RGB systems, each of R G and B follow the same rules. This allows "headroom" and "footroom" for legal filters to produce over and undershoots that will go through the system without being clipped and maintaining the highest possible frequency content.

Some editing packages know about this (e.g. Cinestream and all the high end ones) while the rest tend to ignore it. That means you have to sort it yourself. Just waht tools you use to do this is betyween you and your editing software.

Hope that helps. You'll find alot more along these lines in the URL at the bottom.

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email alan@mugswell.freeserve.co.uk
http://www.chromehead.co.uk/testcards.asp

Snake Plissken
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Joined: Sep 17 2000

Thank you, Alan. Should be easy to stay within these values on Premiere now I know what they are. Ta.

Mark Dicker
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Joined: Aug 31 2000

I found a good document at http://blas.mcmaster.ca/~monger/vidcolor.html

It compares the major colours between computer and video palettes. The RGB values are in percentages but it shouldn't be too difficult to figure out.

Hope it helps

Mark Dicker

[This message has been edited by Mark Dicker (edited 29 October 2001).]

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Mark Dicker
mark@markdickermedia.co.uk