[MF3D.FORUM:1170] Re: Camera design

[Tom Hubin <thubin@xxxxxxxxx>]

Hello Richard,

> > There are ways to tilt the film and make the magnification constant. I
> > think one way is to image 1:1. But that is not very useful to most
> > folks.
> >
> > The other is to use an afocal imaging system. That produces a constant
> > magnification, independent of object distance. A tilted object still
> > creates a tilted image but the magnification is constant. This still
> > meets the Scheimpflug condition.
> 
> I think you  mean "telecentric", not "afocal".  Afocal systems are literally
> "without focal length", like astronomical telescopes with infinite
> conjugates.  

Afocal is exactly what I mean. 

A pair of lenses seperated by the sum of their focal lengths will do.
The Scheimpflug condition is applied twice here. The object creates an
image through the first lens. This image is then used as the object for
the second lens. The result is constant lateral and longitudinal
magnifications at all object distances.  

The film plane must be tilted appropriately for good focus. But no
perspective results. 

This may not meet the needs of the photographers who want a quick
solution to imaging tilted objects, especially if they want some
perspective. In that case, single lens solutions are more convenient.

Tom Hubin
thubin@xxxxxxxxx