Anamorphic lenses will need an additional attribute for a second entrance pupil

Several lens vendors have commented that anamorphic lenses can be considered to have two entrance pupils, though none (AFAIK) have provided for this in the lens metadata currently emitted through lens data ports or through electrical contacts mated to a camera. There may already be provision for dual entrance pupils in DCC helper apps like 3DEqualizer, Syntheyes and/or pftrack.

When dual entrance pupil metadata become available, we should carry it. There are two ways to do this: either define a new pair of entrance pupil metadata with one meta datum for horizontal entrance pupil offset, another other for vertical entrance pupil offset, or change the interpretation of the 'vanilla' entrance pupil offset to be be, say, horizontal EPO if a `verticalEntrancePupilOffset` attribute is present. My personal preference would be for the latter.

Start by locating the existing entrance pupil metadata definition and how lens data ports or electrical contacts represent it. Review whether dual entrance pupils are supported by the mentioned DCC helper apps, then resolve which metadata interpretation to adopt. Done means the chosen representation is specified and supported when dual entrance pupil metadata becomes available.

Written by the indexing model from the issue text.