Glenn ChanREELSony Vegas Tutorials

Color Spaces in Vegas 8

The information in this article applies to Vegas 9 but not Vegas 9. Refer to the color spaces in Vegas 9 article. I recommend upgrading to Vegas 9 as it makes a lot more sense when it comes to levels.

Compositing Gamma

In 32-bit floating point projects, you can switch between a compositing gamma of 2.222 and 1.000. In "1.000" gamma, your image's values are converted from gamma-corrected values to linear light values. This does two things:

A- It gives you optically-correct compositing. Cross-dissolves will be more film-like and diffusion effects will look more correct. See the article on linear light processing in Vegas 8 for examples.

B- The 1.000 mode will cause many of the existing videoFXs to behave differently and to deliver possibly undesirable or weird results. In particular, the "Studio RGB to computer RGB" preset will no longer do what it says.

2.222 will give you the old school Vegas behaviour that you are used to. In most cases, I would stick with 2.222 so that nothing wacky will happen. Optically-correct compositing can be achieved in 2.222 projects by nesting 1.000 projects inside them (see the linear light article for more information).

Levels differences between 8-bit and 32-bit

When you change between 8-bit and 32-bit, Vegas changes more than just the bit depth. Certain codecs like HDV and 10-bit SonyYUV will decode to different levels depending on this setting.

In 8-bit, these codecs will decode to studio RGB levels.
In 32-bit, these codecs will decode to computer RGB levels.

*See the article on color spaces in Vegas for a primer on studio RGB versus computer RGB levels.

Because the codec behaviour is different in 8-bit versus 32-bit projects, you will see differences in color between 8-bit and 32-bit. Codecs like DV and Cineform do not have this behaviour- they decode to the same levels regardless of the bit depth of the Vegas project. Certain footage in 32-bit projects may look "better"/different, but this is only because the levels are being decoded differently.

This can be an issue when rendering or previewing via DV passthrough. When previewing through a DV device, Vegas' DV codec will want to see studio RGB levels. In 32-bit mode, HDV footage will decode to computer RGB levels, which is inappropriate for Vegas' DV codec. This is something to watch out for. In that particular case, you may want to convert the HDV footage to studio RGB levels by applying a "computer RGB to studio RGB" conversion preset in the Levels (or Color Corrector) videoFX.

Also note that flipping between the 32-bit and 8-bit modes in Vegas can potentially give you problems. I believe the intention of Vegas 8 is that you pick either mode and do not flip between them. However, it can be desirable to flip to a 8-bit project for the faster performance and then to 32-bit when you render. The problem is that the levels of the footage can change on you if you do this.

Some workarounds would be:

A- Know when your levels are wrong and ignore it when it does not matter. You may only need to watch your levels when you are rendering. In that case, determine what levels your codec would like to see. If necessary, apply a Levels videoFX with the right studio RGB<-->computer RGB conversion preset (there are presets to convert between the two different types of levels).
*Keep in mind that the presets are broken if your project's compositing gamma is 1.000. You will need to use different numbers.

B- Transcode HDV clips to Cineform either through scripting tools (such as VASST Gearshift) or Cineform's capture application, which transcodes as you capture. Cineform decodes to the same levels regardless of what bit depth the project is in.

C- Work in an 8-bit project. This will give you the same behaviour as previous versions of Vegas. (Ok, so this is not really a workaround.)

The following table describes the behaviour of various codecs and preview methods. It also indicates whether the codec behaviour changes in 8-bit versus 32-bit projects.

Name of format / codec In 8-bit project In 32-bit project
AVC HD via Main Concept MPEG-4 (Vegas' default MPEG-4 codec)

Studio RGB. (Decodes to and wants to see studio RGB levels.)

Computer RGB. (Decodes to and wants to see computer RGB levels.)

HDV, Main Concept MPEG-2 (e.g. used for DVD encodes out of Vegas)
Sony YUV, 10-bit Sony YUV
Cineform (captured through their tools) Studio RGB. (Decodes to and wants to see studio RGB levels.) *Some versions of Cineform allow you to change the preferences/settings so that it decodes to and expects computer RGB levels. However, the default for Cineform in Vegas is studio RGB.
Vegas DV codec Studio RGB. (Decodes to and wants to see studio RGB levels.)
Third party DV codecs Depends on codec. May use computer RGB or studio RGB levels.
Still images (e.g. JPEG, PNG, GIF) Computer RGB. (Decodes to and wants to see computer RGB levels.)
Windows Media (from within Vegas, not within Windows Media Encoder)
Uncompressed (8-bit); rendering to Video for Windows AVI; rendering from an 8-bit project Passes levels through. Will decode to whatever levels it receives. e.g. If you feed the codec studio RGB levels, it will decode to studio RGB levels. If you feed the codec computer RGB levels, it will decode to computer RGB levels. Passes levels through. Cannot encode 8-bit uncompressed from 32-bit project.

Uncompressed (32-bit); rendering to Video for Windows AVI; rendering from an 32-bit project

Not to be confused with Aja/Blackmagic/Apple uncompressed codecs.

Passes levels through*. Cannot encode 32-bit uncompressed from 8-bit project. Passes levels through*.

*There seems to be a bug if rendering to this format from a project with 2.222 compositing gamma. The encoded values seem to have a significant gamma shift (a Levels FX with a gamma of 0.45 seems to undo this).

**Subtle differences occur in levels (+-1 RGB out of a 0-255 range) depending on whether the project is 32-bit or 8-bit.

Quicktime codecs (via Quicktime import/expect from Vegas) The majority of codecs use computer RGB. (Decodes to and wants to see computer RGB levels.) But not all codecs do this.
DVCPRO HD via Raylight ?Studio RGB? (I have not checked personally.)
Default background 'Decodes' to computer RGB. The default background color is 0 0 0 RGB, which is an ILLEGAL black and inappropriate for codecs that expect studio RGB. Fix this by adding a solid color media generator that creates a 16 16 16 RGB black for studio RGB codecs.
Color bars media generator 'Decodes' to Studio RGB.

Preview Method In 8-bit project In 32-bit project
Video Preview window Computer RGB. (Wants to see computer RGB levels.)
via DV device (e.g. camcorder); using Vegas DV codec Studio RGB. (Wants to see studio RGB levels.)
via DV device (e.g. camcorder); using third party DV codec Depends on codec. May use computer RGB or studio RGB levels.
Windows Secondary Display May use computer RGB or studio RGB levels. The setting is under Preferences -> Preview Device (tab) -> Color management (checkbox) -> Use Studio RGB (16 to 235). If the Use Studio RGB checkbox is active and checked, the windows secondary display will want to see studio RGB levels.
Aja Video Device ?Studio RGB? (I do not know.) ?Computer RGB? (I do not know.)

If the preview display/method is fed with values of the wrong color space/levels, then it will display an inaccurate image. This can be ok as long as you know that the preview is inaccurate (sometimes you do not need a 100% accurate preview).

Example Workflow - 8-Bit Vegas project with mostly video clips

Suppose you have DV, HDV, and JPEG images in your timeline. For 8-bit projects, I recommend converting everything to studio RGB levels.

Looking at the codec table, we see that DV and HDV both decode to studio RGB levels in 8-bit projects. We do not necessarily have to do anything to these media. However, almost all DV and HDV cameras will record illegal superwhite values above 235 RGB. You may wish to apply color correction to these clips to deal with these illegal values.

We see that JPEG images decode to computer RGB levels. Since we want studio RGB levels, we will apply the "computer RGB to studio RGB" Color Corrector (or Levels) FX preset to all our JPEG images. One way to do this is to select JPEG images in the timeline, have the Video FX window open (Alt + 8), and drag the preset from the Video FX window onto selected clips/events on the timeline.

For previewing, the Video Preview window will be inaccurate. From the codec table, we see that the Video Preview window expects/wants to see computer RGB levels. However, it is receiving studio RGB levels. So, the image it displays will be incorrect. For accurate monitoring, preview through a DV/firewire device to an external monitor. To send the video to the camera, the material has to be compressed into DV. The default DV codec (the Sony Vegas DV codec) expects studio RGB levels. We are feeding studio RGB levels, so we don't have to do anything.

When rendering the final project, we have to check to see what codec we're rendering to and what levels it expects.

If the project is for DVD or broadcast output, we should do something about the default background color (0 0 0 RGB). This is an ILLEGAL black and can cause the picture to roll on very old TV sets. To fix this, we add a solid color media generator to make a black of 16 16 16 RGB and put this onto the bottommost track in Vegas. Similarly, when we want to generate white, we need to use 235 235 235 RGB instead of 255 255 255 RGB.

Example workflow - 8-bit project with mostly still images

This is like the example above, except we convert our events into computer RGB levels in the timeline. We leave still image formats like JPEG alone, and we apply "studio RGB to computer RGB" Color Corrector FX presets to DV and HDV clips.

For previewing, we use the Video Preview window in Vegas. If this project is also for video output, then we will want to monitor on an external monitor via DV/firewire. Because Vegas' default DV codec expects studio RGB levels, we will need to apply a "computer RGB to studio RGB" levels FX onto Video Output FX to preview with the correct levels. Make sure that you disable this FX whenever rendering to a new track!!!

When rendering to codecs/formats that expect studio RGB levels, we will need to nest the project and apply a "computer RGB to studio RGB" Color Corrector FX preset.

Example workflow - 32-bit project with mostly video clips

For 32-bit projects, I recommend:

For still images, HDV and AVC HD clips, we do not need to do anything to them since they decode to computer RGB. DV media and Cineform clips captured via Cineform's tools decode to studio RGB levels. We need to convert these media to computer RGB levels.

For previewing, use the Windows Secondary Display as the preview device / external monitor. In the settings, make sure that the studio RGB checkbox under color management is unchecked. Previewing through a DV device will be inaccurate.

When rendering to particular formats, it may be necessary to nest the project and apply a "computer RGB to studio RGB" preset as necessary.

You may wish to do your cutting with the project set to 8-bit mode. However, you will need to ignore any incorrect (or correct) color you see since some codecs behave different in 32-bit projects.

32-bit Workflow B

Suppose that you do want to work in 32-bit and preview to an external monitor through a DV device. This can be useful if you intend on outputting SD.

In this case, follow the previous workflow except apply a "computer RGB to studio RGB" preset onto Video Output FX. But watch out!! Do NOT use "render to new track" with this FX applied. You need to remember to disable Video Output FX when rendering to a new track.

When rendering the final project, it may be necessary to convert the studio RGB levels to computer RGB levels via nesting.



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