Saturday, May 17, 2008

Setup and Digital Video

In a world where digital and anolog signals mix together.  I am curious when setup (7.5ire) needs to be added to the signal.  How smart is todays video equipment in correctly adding and subtracting setup from a signal?  If anyone is an expert, please leave a comment.

2 comments:

Anonymous said...

It depends on your intention when it comes ot adding setup. Digital video does not use set up and for that matter analog video doesn't actually need setup anymore. 7.5 ire was something done in the United States in the early 60's I believe to compensate in a lack of commercially made television sets to handle black levels. Today's video cameras shoot raw video signals with no altering off the setup level. Conventional Broadcast Engineers still design plants to handle both analog and digital signals at the same time because some satellite systems, yes some still exist in the anolog environment. On the opposite end of the spectrum...video cameras at the "just above" consumer level like the Sony PD170 add setup to the DV25 video signal. Why? I'm not sure. Though the actual difference between a signal with and without setup is very small, to the point where engineers and colorists are the only people who can truly tell a difference, I wouldn't worry to much about equipment adding and subtracting setup. Today's equipment is pretty advanced in detecting setup in a video signal, the danger is when a signal has setup added and it passes via an analog connection to another device that is setup to automatically add setup. I've seen this happen first hand with the result being pushed black levels or what I like to refer to as a washed out bottom end. I don't consider myself an expert in this category, but the question is valid. I hope someone else can respond to further your question.
_ Tom Hugo / Advanced Concept Video

Anonymous said...

What is important is that the bars or calibration signal reflect the true levels of the video signal. If you are not going to use setup, do not use SMPTE bars or your blacks will look crushed. It is important that everyone down the chain from production to post to duplication knows what the setup level is.
The confusion I'm starting to see results from a lack of standards. Some are using 7.5, some 0, and this needs to be addressed so that what viewers see on their screens matches what the creatives intended.

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