Originally Posted by
Doremus Scudder
This is the correct thing to do if you want to keep parallel verticals in the scene parallel on the film. Pointing the camera down with the pan/tilt head on your tripod would result in keystoning, i.e., converging verticals; in this case converging toward the bottom of the image.
Here's where I'm not quite sure what you did. If you were using asymmetrical swings, your axis lines should be vertical; you've got horizontal axis lines in your illustration, so they don't quite jibe with your description...
Also, I'm not sure what you mean by swinging the back so that "the right side was further away and the left side closer." Closer to what is the question: Closer to you? Or closer to the scene?
If you were trying to get the plane of sharp focus aligned with the plane of the barn wall, then you would swing the back farther from parallel to the plane of the wall, i.e., in the opposite direction that you would swing it to make it closer to parallel (God, this is hard to describe clearly; maybe someone else can give me a better choice of words?)
Remember, if you want to align the plane of sharp focus with a subject plane, "the lens looks, the back 'backs away'."
I'm assuming that's what you did; brought the plane of sharp focus to align with the plane of the wall. This brings the wall into better focus, but causes horizontal parallel lines to converge (you're moving the back in relation to the subject, hence image perspective changes).
If, however, you swung the back the opposite direction, i.e., in the direction of more (or completely) parallel to the barn wall, you are ensuring that horizontal parallel lines will be rendered parallel (or more so) on the film. But, doing this moves the plane of sharp focus at an even more oblique angle to the wall of the barn, so if you want some to keep it all in sharp focus, you need to compensate with front swing; moving the plane of focus back in alignment with the barn wall. You'd do this by swinging the front standard in the opposite direction you swung the back.
Hope that all makes sense,
Doremus
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