HDV:What You NEED to Know
This tutorial will help you to know more about video
levels and the "Levels" filter in Sony Vegas®
software. Understanding how to adjust and manipulate video levels
will help put you in control of what the audience sees. By understanding
levels, you will be able to avoid undesirable or unintentional clipping
in the image. It will also assist you in improving your footage.
To achieve good video levels with the Levels filter, you will first need to know what those levels should be.
What Video Levels DV Cameras Record At
DV cameras typically record "superwhites"- values above digital white level. These are "illegal" values which may not be displayed correctly when broadcast or played on a DVD player. Broadcasters may reject your master if it has too many superwhites (this may depend on the broadcaster). If your target delivery format is DVD, some (but not all) DVD players will clip superwhites. Clipped white values will lack detail and may look ugly, being washed out or even appear to vibrate.
Some DV cameras such as the PD150, DSR250, and DVX100 have menu settings named something similar to "7.5% setup". What this setting actually does is to raise the digital black level recorded to a non-standard digital black level (see Adam Wilt's DV FAQ for more detail). This 'fake setup' could be problematic. The Levels filter may be employed to repair any difficulty caused by the non-standard levels.
DV cameras will also record values slightly under digital black level due to digital compression. You should let those values fall under digital black level.
Proper Video Levels
The following paragraphs will describe what video levels should be for the analog and digital domains.
Proper Levels for Computer Formats (i.e. web streaming)
Computer white level should be at 255 255 255
RGB. Black level should be at 0 0 0 RGB. Sony Vegas calls this "computer RGB".
Proper Digital White and Black Level
In Sony Vegas, proper digital levels depends on the DV codec being used.
Sony, Canopus DV codecs: Black level should be at 16 16 16 RGB. White level should be at 235 235 235 RGB. Vegas calls this "Studio RGB (16 to 235)".
Microsoft, Matrox, MainConcept, Apple Quicktime DV codecs: Blacks level should be at 0 0 0 RGB. White level should be at 255 255 255 RGB.
This tutorial assumes you are using the Sony DV codec used by Sony Vegas, which is the codec you should use (at least for this tutorial). To ensure that you are using the Sony DV codec, go to Options --> Preferences. Under the General tab, check "Ignore third party DV codecs", uncheck "Use Microsoft DV codec".
Also check the settings for Vegas' Video Scopes. These settings affect how digital black levels are represented on the Waveform display in the Video Scopes.
Digital white level corresponds to 100 on the Waveform display (of the Video Scopes) as long as the "Studio RGB (16 to 235)" setting is correctly checked/unchecked.
In the Video Preview window in Vegas, digital white level will appear a 235 235 235 RGB. This will be problematic for monitoring on a computer display, as whites may look a little grey-ish. The same applies for black. Digital black level will appear as 16 16 16 RGB on your computer monitor (where 0 0 0 RGB is the lowest your computer monitor can go). What this means is that you should view your image on an external monitor (scroll down for HDV information). The most common external monitor to use is a consumer television hooked up to your DV camera (which can act as a digital-analog converter; most can do this). To do this:
There is a tutorial on connecting an external monitor to your camcorder or other Firewire converting device here.
For HDV editing, you may want to a secondary Windows display instead. In this case, enable the color management settings so that video is displayed correctly. In the Preview Device settings (Options --> Preferences --> Preview Device):
For NTSC, analog white level should be at 100 IRE.
For NTSC (other than Japan), analog
black level should be at 7.5 IRE. This is also referred to as (7.5 IRE)
"setup" and (7.5 IRE) "pedestal".
PAL has analog white level at 100 IRE, and analog black level at 0 IRE.
Most consumer and "prosumer" video equipment for the North American market will translate proper digital black level to 0 IRE (instead of 7.5 IRE). This will result in crushed/clipped shadow detail and an image that is slightly too dark.
DVD players will translate proper digital black level to 7.5 IRE.
This issue is important because it can affect how your footage appears. If your digital-analog converter does not add 7.5 IRE setup, you will be monitoring with an image that is too dark and has clipped shadow detail.
If you are monitoring via a consumer DV camera (that converts digital black level to 0 IRE instead of 7.5 IRE) and your target format is DVD:
If you are targeting an analog format and your digital-analog converter converts digital black level to 0IRE, then things get tricky. You have a few options:
A- If it is an analog dub (i.e. a VHS for client
proofing), then it may be OK to let the incorrect conversion occur.
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