Unity gain means keeping the levels - both video (contrast, brightness & color) and audio consistent throughout the path of production and post-production, from the recording of footage in the field all the way to the playback of the final program, whether it be broadcast or viewed on a recorded media like DVD.

Look at the many steps that footage typically goes through before getting to air or distribution.

And these steps are often further sub-divided or expanded. 

For example, portions of the video during the editing might be sent off to the graphics department for added effects work — with the resultant composited footage then brought back into the editing.

And after a program is finally edited, the sound is often stripped off and sent to an audio mixing facility for “sweetening.”  Then that new mix is brought back into the edit system and conformed to the picture before the program is laid off to the edited master tape.

You might ask, does maintaining unity gain really matter in this digital age?  You might be thinking, what with all the computers being used throughout, can’t one just adjust levels digitally as needed at any point along the way?

The problem with that thinking is that making radical adjustments at any stage in the pathway can introduce “noise” in either the video or audio.  Plus, you can correct only so far. 

Here is an everyday example of what I am talking about.  You may have tested the limits yourself when working on an underexposed digital photo in Photoshop or similar graphic program.  Sure, the computer software allows you a lot of correction ability that was unimaginable just a few years ago.  But chances are, if the photo is seriously underexposed or “out of whack” color-wise, you will be limited as to how much correction you can apply.  Despite your best efforts, chances are you will not be able to get the image to look very good.

Now, let’s look again at the production/post-production path chart – and think of every step as a point where the picture “gets taken” by your camera - an opportunity to affect the signal . . .
 
See the importance of maintaining consistency - or unity gain?

And the same goes for audio.

So how does one maintain consistency throughout the production and post-production chain?  How do we know what the intended or proper Picture and Audio levels are at any point in the production/post production process?   How do we know what is real?

The two basic metrics used to confirm proper levels are SMPTE (Society of Motion Picture and Television Engineers) bars for video, and 1K hertz tone for audio.  Check out this link for more details on those: http://tinyurl.com/59xckj

That is why it is standard procedure to lay down at least 30-secs of bars and tone at the beginning of every tape shot in the field and on every edit master and subsequent dub master.  Bars & Tone provide an industry reference.  When you release your videotape for broadcast or duplication, the 30 seconds of Bars & Tone at the beginning of your tape insures all of your hard work will be reproduced accurately.

For those dealing directly with the technical aspects of production and post-production, there are other intricacies to keep in mind when calibrating equipment in the signal path to bars and tone.  For video, there is component video http://tinyurl.com/pgvyh, SDI (serial digital interface) http://tinyurl.com/2u4wvp and of course the burgeoning High Definition field http://tinyurl.com/6c7d8j  &  http://tinyurl.com/5s6y8h

Also, remember to check the calibration of your “reference set-up equipment.”  About once a month check the calibration of your color monitor, waveform/Vector scope and the Audio Meter.

For audio there is the variable of whether the meter you are using is a VU (volume units) or PPM (Peak Program Meter).  Read more about that here: http://tinyurl.com/6xzp3d

And there is also the realm of digital audio to consider.  Formats such as AES http://tinyurl.com/676et3  and Dolby 5.1 “surround sound” http://tinyurl.com/onwte

One last note about audio meters and tone.  If the audio meter is “summed Mono” (Left & Right channels combined), the meter will read 3 dB hot when playing tone on both audio channels at the same time.  Always play the audio channels one at a time to confirm proper Tone level on a “Mono Meter”.

Suffice it to say that unity gain is important to always keep in mind whether you work in a large production facility or an indie production boutique.  Almost every broadcast and cable network insists on a strict quality control review of programs being considered for air.

If unity gain has not been carefully maintained throughout the production control, I can almost guarantee you that issues will arise that will result in the program being rejected.  And as a producer or technician, that is something you do not want to hear.

So, avoid that frustration (and added expense).  Watch your levels closely throughout the production and post-production process.  Insist on unity gain throughout.

Your comments are encouraged below.

Feel free to contact Chris Vazquez at chris.designsmith@verizon.net or 301-953-1427.

Other articles you might be interested in:

Is there generation loss in digibeta?  Check out Chris’ article: http://tinyurl.com/6yd6gn

Curious about setting up your editing timeline correctly?  Check out David’s blog: http://tinyurl.com/5mbl8u

Need CD, DVD or tape duplication?  Contact David Ryan at dryan@videolabs.net or 301-217-0000 x104