Lens Metadata

Composite imagery, once relatively rare in motion picture production, is becoming ubiquitous. Scenes increasingly are being created from multiple elements, often a combination of real and virtual subjects.  The inclusion of CGI elements into production cinematography involves the creation of a “virtual” camera that must closely emulate the camera shooting principal photography. When such scenes were “locked off” and thus static, it was possible to “deduce” much of the information about the status of the lens that made the image. The trend of recent years for highly dynamic camera moves during a shot have made the deductive approach impossible. It is now necessary to record, on a frame-by-frame basis, a great deal of data about the status of the taking lens: focal length, aperture, focus distance, shutter angle, etc.  The need is even greater for 3-D production where convergence and inter-axial data are crucial and still further complicated when “tilting” and “shifting” lens axis are included. 

This group will explore:

• the objectives and advantages of having these data

• an effective regime for acquiring, preserving, disseminating and using these data

• the current state of the art of metadata in the industry and endeavor to recommend an effective path forward

• whether a recommended practice protocol, or a SMPTE standard is desirable and achievable

Appended to this are selected documents from the working groups library. It will be obvious that a considerable effort has been made by the ASC Technology Committee to attempt to define the scope of the task of describing an architecture for this technology.

There is increasing support in modern cameras and lenses for the ability to electronically report settings and record them automatically for future reference.  Information reported from lenses, cameras, and camera rigs include such parameters as lens serial number, camera ID, aperture, focus, shutter setting, and convergence and interaxial for 3D.  Various strategies and workflows exist for the use or omission of such information and including it with the recorded image files or and/or separate files.  The benefits and potential pitfalls of various approaches being used or considered are examined, as well as work being done within SMPTE to address such issues.