The pleasures of orthogonality

Posted by Piers Cawley on Dec 12, 2003

Focussing a large format camera can be a tricky process if you’re not used to it. Unless you have a remarkably simple scene there’s usually a period of frantic adjustment of swings and tilts to try and get the plane of focus running through the most important elements of the scene. Most large format photographers will have heard of the Scheimpflug Rule which says that the plane of sharp focus, the film plane and the lens plane must all intersect in a single line. This is one of those useful in theory but useless in practice maxims.

The problem is that you can end up chasing your tail. Adjusting the focus moves the the line of intersection, which means that the plane of sharp focus is suddenly missing the nearest point, so you adjust the tilt to take that into account, but that changes the angle of the plane of sharp focus so it misses the far point, so you adjust the focus, but…