Bob,
Allow me to comment on your comments in the interest of clarification, especially for those just engaging with the subject of camera movements.
1: perspective only changes in photography with the angle of the Camera to the subject.
It's precisely the strict use of the term "perspective" to refer
only to angles of view from center of lens to subject that is muddying the waters here. Many (if not most) of us use the term more loosely to also refer to the change in image shape on the ground glass when back swings/tilts are applied. This change in image shape is due to a change in the geometric projection onto the film and may possibly be more accurately described as distortion or shape change. Nevertheless, the use of the term "perspective" to describe this is so widespread that it seems pointless to insist on the distinction.
2; there are 2 types of camera adjustments, direct or indirect.
A: direct movement use front and/or rear shifts and rise/fall only.
B; indirect movement uses front and/or rear tilts and swings only.
C: direct movement is done with a level camera and then the front and back sliding movement.
To be perfectly honest, I've never heard the different types of movements categorized as "direct" and "indirect." Certainly rise-fall/shift is fundamentally different from tilt/swing. I'm curious where you got the terms. I have Stoebl and a few other guides to movements and don't seem to remember coming across them. FWIW, neither kind of movement requires any particular orientation of the camera. See below.
D; indirect movements normally have an inclined camera and then tilts and swings.
E: tilting the camera up to include, for example, the top of the building, requires tilting the back to parallel to the subject.
FWIW, I use tilts and swings with the camera leveled about 90% of the time, even in architectural work. The notion that tilts and swings are usually applied when the camera is not leveled is really off-the-mark. Maybe you're referring to the "point-and-tilt/swing" technique to achieve more rise-fall/shift? This technique can be used alone or in conjunction with rise-fall/shift and results in both standards being parallel, i.e., resulting in no effective tilt or swing (one just uses the tit/swing to get the standards parallel) and retaining the parallelism between film, lens and focus planes. Using tilt or swing alone is a very different thing and reorients the plane of sharp focus to something other than parallel to the film and lens planes.
3; there are 3 types of camera movements, base,axis and asymmetrical.
With axis tilts the subject does not shift position. With base shifts it does. Asymmetrical are base shifts that prevent subject shifts.
Axis lens tilts do not use up image circle.
Please note that with axis tilts/swings that it is only the
center of the image that does not shift position. The sides of the image get moved around and focus shifts there. Base tilts (I know of no base swings...) move the entire standard, so general refocusing is required. Asymmetrical movements are just axis tilts/swings with the axis displaced to one end/side or the other to increase the distance between focus points (one of which always has to be on the axis) and, supposedly facilitate more rapid application of the movement. I'm about as fast with all the different kinds of movements.
On to "using up the image circle"... Swinging or tilting the lens stage moves the center of the image circle from film center, displacing it up, down or sideways. If you swing or tilt enough, you'll run out of image circle to cover the film, since it will be pointing somewhere else, resulting in vignetting. This repositioning of the cone of light projected by the lens which can end up with part of the film outside the circle of coverage is what we're talking about when we say, "swinging and tilting the lens stage uses up image circle." This is important even if we don't vignette, since many lenses are not nearly as sharp at the edges of the image circle as they are in the center.
[Re: back movements changing perspective.] No, it controls subject shape as well as plane of sharp focus. Perspective is controlled by the angle of the camera to the subject. back tilts and swings control subject shape!
Yes to everyone here. We're too busy arguing semantics. It is precisely the "change in subject shape" that many of us call a "change in perspective." Certainly, correcting convergence of parallel lines (one of the main uses of back movements) qualifies as a change in perspective in my book. One is moving the vanishing point around in the image, which Renaissance painters would have almost certainly described as changing perspective. Why not accept the use of the term "perspective" to refer to this as well? I think it would avoid a lot of confusion.
That isn’t what I said but to correct your statement, image circle changes with aperture used and distance focused on, so your statement is partially correct. It does not change with camera movement.
Again, we're discussing two different things. I think we all agree that camera movements
per se do not change the size of the image circle. What does happen, however, is that the position of the image circle relative to the film changes a lot with rise-fall/shift and front tilts/swings. Since these latter present the danger of vignetting, the fact that the image circle is being displaced is good to keep in mind when applying movements. I agree, though, that we need to be more precise here and use some descriptor that is more precise and shows that we mean that the image circle is being moved around.
Thanks for the opportunity to clarify my description of things.
Best,
Doremus
