The GEOMETRY Workflow - 3D Postproduction: Stereoscopic Workflows and Techniques - page 104

4.5.4 Geometry Decision Lists
In this topic, we use the term Geometry Decision List or “GDL” to describe
the document containing descriptions of the geometry corrections made to
footage as recommended in the Geometry Review Report. These documents
should be as complex and as complete as they need to be for your show.
Teams use GDLs along with decision lists from other workl ows to integrate
geometry i xes into the show master. Metadata (e.g., in the form of notes, i le
header data) rel ecting geometry corrections made to imagery must travel
with the imagery so that, if necessary, geometry settings can be revisited or
reverted back to previous versions.
Artifacts
Artifacts are dei ned as perceptible issue in imagery that cannot be otherwise
identii ed or explained. Artifacts occur in 2D as well as 3D. An artifact is only an
issue if it affects comfort and continuity. Examples of artifacts include:
• Blurring
• Pixel Hits
• Video Noise
• Color shifting
• Colorbanding
• Inconsistent l ares/rel ections
• Sudden changes in depth, geometry or color
• Otherwise unexplainable visual phenomenon
As with all other issues, artifacts are only an issue if your team determines that
they fail to meet the criteria for good 3D. It is not unusual, for example, to have
a single shot containing:
• known (correctable) geometry issues like keystoning and vertical misalignment
• known (correctable) color issues such as mismatched lens l ares, mirror color
wedges and polarization differences
• known (gradable) depth issues such as excessive negative parallax
• unidentii able/unexplainable issues (artifacts)
As with all other issues, artifacts are only an issue if your team determines that
they fail to meet the criteria for Good 3D.