Hi, Valentin,
Thanks for the two references on panoramic concepts.
The information there seems to suggest "planar" as a term to identify what is elsewhere in photography called a "rectilinear" projection.
That is in fact the type of projection we generally (until we get into such areas as "fisheye" lenses) hope to attain in "normal" photography. In tests of lenses, we report on the degree to which they depart from that type of projection (the "geometric distortion" part of the report).
A rectilinear projection has two important properties:
- any straight line in the three-dimensional scene will be rendered as a straight line in the image
- the array of object points lying in any plane of the scene that is parallel to the plane of the film will form in the image a "precise miniature" of that "planar array".
For example, if the photograph is of the front face of a building, with all of its features essentially lying in a plane, and that plane is parallel to the plane of the film in the camera, then the image of that building face will be a perfect miniature of the building face itself, just like an architect's "elevation" rendering of the building face. The image of the building face will be, in the sense of the term used in formal geometry, "similar" to the building face itself (all distances in the image proportional to those of the object, all angles between lines in the image identical to those of the object).
In the various sophisticated "panoramic assembly" software we have available today, which can assemble from multiple images a composite image, allowing us to simulate the results of various projections, I don't know how that projection choice (if offered) is "labeled".
Here is another handy reference on projections as applied to panoramic photography. It discusses the "rectilinear" projection.
http://www.cambridgeincolour.com/tutorials/image-projections.htm
Best regards,
Doug
