How to use the output tab

Target file
Edge/shift
Gamma, range, nclc
Top field first, progressive
Edge Color
Video output
Sound output
Stretch sides
Canvas
Inspector
Output preview

Target file

Select name and location of the output movie. This way you can overrule the default location set in the preferences.

Edge/shift

For most project types this allows you to shift the image. Use this if the movie has edges of unequal thickness.
Standards conversion allows scaling. In this case you can define an edge for the output movie (an inset into the dimensions set in the Project pane, "Custom" only).
In most cases you can use one of the standards conversion presets which also set the edge in the output pane. In custom standards conversion mode you can get creative.
Usually the clean input (in dimensions minus crop) is mapped on the clean output (out dimensions minus edge). IOW the edge you set affects the scaling of the image.

Gamma, range, nclc

Output gamma is usually 2.0 (see "nclc"). Use 1.8 for Apple Component (direct) or RGB-based QuickTime Movie export.
Range is usually video range, except again for Apple Component format.
"nclc" encodes all three of gamma, monitor phospors and RGB->YCbCr matrix. The gamma is formally 2.2 but actually closer to 2.0. The other two components affect strongly saturated colors only.
As always, if you don't know what to set use default values. Setting out values equal to in values ensures that no color processing is performed.

Top field first, progressive

For the web you want progressive out.
If you want interlaced out uncheck "Progressive". Interlaced is usually better for TV viewing.
"Top field first" is left unchecked for DV out, checked in most other cases.
If you do standards conversion, you need to select "Custom" if you want to set a different interlace out.

Edge color

The edge color is used if the color would otherwise be undefined at an output edge.
This depends on the "paint edge color over input edge" preference. By default it is assumed that the input edge may be used to fill image parts (without extension or warping) that would otherwise be undefined. Even then the edge color may be needed for parts that are not covered by the mapping of the input frame to the output frame.

Video output

Choose "Direct" for fast and mild compression. Output is a QT movie.
DV and DVCProHD are available only if the dimensions are right.
'Direct' uses multiple CPU cores which makes it faster than export except for ProRes 422 which was optimized internally by Apple.
Additionally three uncompressed pixel formats are available (2vuy, yuv2, y420).

Choose "Export" if you want all QT options or if you want to export to another file format. Not all 3rd party exporters are supported.
"iPod" or "AppleTV" is best selected from the standards conversion tab (if you do standards conversion) and DV export is only available if the output movie has the right frame rate (scaling is allowed).

Sound output

Usually you just copy the sound. If you want to compress choose one of the other options (normally that would be "QuickTime Audio").
Sometimes the sound must be mixed down even for copy (for example, if movie speed changes). This results in uncompressed sound getting added to the movie.
"QuickTime Audio" adds a sound track to the output movie. The other options create a separate sound file.
In case of video export the video compressor usually handles the sound too. In this case the sound out options in the output pane are greyed out.
Unchecking "Sound" in the QuickTime Export dialog allows you to compress the video and just copy the sound.
The "dual mono to stereo" problem is dealt with in the input pane. Before conversion the mono tracks (or channels in one track) are marked as L/R which causes QuickTime to treat them as stereo sound.

Stretch sides

Horizontal stretch can be used to stretch SD video (PAL or NTSC size) to HD. The idea is to leave the center of the frame unchanged while stretching the left and ride sides.
If the action is mainly in the center this may result in a better viewing experience than having black pillar boxes at the sides or stretching the entire image (which makes people look fat).
Normally the use is restricted to talking head video or video with sidebars containing static text or some other static content.

In most cases you apply this option in conjunction with export in letterbox or crop mode (using QTMovie, DV or MPEG4 export). In the anamorpic preferences "Use input aspect ratio" and "Set output aspect ratio" must be checked.
Shrinking sides is also possible. One case that comes to mind is putting a movie in Cinema 21:9 format in HD format.
Normally the algorithm preferres shrinking over stretching except when you are horizontally upscaling a movie with landscape aspect ratio.
If you don't do standards conversion and use direct write a small shrink or stretch may fill the output canvas or prevent loss of a small edge of the input movie in some cases.

In the anamorphic preferences you set the size of the image part that gets stretched. See Preferences Help for an example.
A small stretched edge preserves more of the center of the movie, but it also gets distorted more.

Canvas

If you do standards conversion with "direct" compression you can use a canvas. This is just like the size options offered by QuickTime Movie Export.
The movie, as defined by the standards conversion size, the output clip and the various settings that determine out pixel aspect ratio, is projected on the canvas according to the scaling mode.

Tip: if you just want to set the pixel aspect ratio of the output movie, make the canvas dimensions and clip equal to the output values and use "Simple scale".
Remark: if aspect ratio is preserved the output dimensions and output clip are irrelevant because the input movie is effectively projected on the canvas according to the scaling mode. If aspect ratio is not preserved only the relative magnitude of clip vs output dimensions matters.

The combination of output dimensions, output clip, "simple scale" mode and canvas properties is very powerful: it allows you to create any media size with any clip or edge and aspect ratio.

Inspector

Some elements of the output pane (info, color, dimensions) have been moved to the Inspector in v3.6.
The "Test render" button lets you create a 10s preview of the movie starting at the current preview time. It is opened looping in QT Player 7.

Output preview

You can preview the output in a separate window. Most settings are reflected in the preview. Slight differences are possible because the preview doesn't preflight the entire movie.
Noise reduction (slow) is not visible in the preview. Use the "Test Render" button instead.