To Len and Clayton:

Quote Originally Posted by Len Robertson View Post
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Clayton (or anyone), does my suggestion to Roberto to make a focusing scale based on actual distance measurements corresponding the those marked on his gears seem the correct way to get his Cirkut so he can focus it?

Len
Well, as a matter of fact, there's a problem of focusing when used in panoramic way. In my camera, the film plane, with the panoramic outfit, is about 4.4 mm more away than the ground glass plane in "normal mode" (goes behind the ground glass plane); therefore, focusing on the ground glass and then fitting the Cirkut box gives deceptive results (out of focus). But, by knowing in advance the value of the difference among the two planes, is possible (with some artifact) to work out a "supplementary scale" for the "panoramic way". And, as reported further on, the program could help also for this issue.

As said previously, I suppose that (making reference to the drawing in http://digilander.libero.it/foto_ras...ut_pattern.jpg) the camera should rotate around the axis of the lens in E (supposing the axis is there...), but actually, as I can see in pictures of other Cirkut cameras "at work" (and in mine too), the rotation is around the point F (pivot of the gear plate), and the distance between F and E depends on the diameter of A (the "small gear" actuated by the spring motor), with the camera connected to the tripod by the screw G, fitted in a sliding wooden plate, so that B and A can stay in contact.
But all the same I agree that for short focal lenghts and for a subject at infinite the axis of rotation is not so important: your experience is worth a thousand times the "theory" !
Furthermore, this issue seems less important with respect to panoramic digital rotating cameras, because in Cirkut cameras not the full frame is involved, but only the narrow central slit.
The problem is assembling the correct gear with the correct distance from the subject, for a given lens and for a given "size" of Cirkut camera.
The program, as I said, works, and works in DOS ("command prompt", under cmd.exe, in Windows).
It considers (and asks for typing) a number of "variables"; for a few of them is probably unclear how to deal with. But first it asks if you want to measure the subject distance from FILM PLANE or, alternatively, from the REAR NODAL POINT : can we suppose, just for the sake of convenience, that the latter is approximately on E ? In case of a subject at infinite, even if the RNP is not exactly in E, the shift seems not very significant. But, how can we type "infinite" at the "command line" ? With a very very high value in inches (or mm) ? one million inches?
The "variables" are:
1. - the actual focal lenght : no problem;
2. - the "large gear radius" : does it mean the toothed disc B ?
3. - the "Diameter of film drum with average amount of film": clear and no problem;
4. - the "Perpendicular distance from center of small gear to the LENS AXIS": assuming that the "small gear" is A, does it mean the distance between E and H ?
5. - Perpendicular distance from center of small gear to the FILM PLANE (NEGATIVE IF FILM PLANE IS BEHIND GEAR): does it mean the distance between H and C ? If we refer to the drawing, the value should be positive, I suppose;
6. - the "Slit width": clear, no problem;
7. - the "Gear pitch" : what does it mean ? Is it the distance between two contiguous teeth of the (large ? small ?) gear or something else ?

The output of the program is a file in .txt format (gearsOutput.txt), not well readable (at least, in my PC...) if opened as such in "Notepad" (see an example in http://digilander.libero.it/foto_ras/gearsOutput1.pdf). But if opened with Word is perfectly understandable : see an example in http://digilander.libero.it/foto_ras/gearsOutput2.pdf. Please note that the values given in input were "imaginary" and fictitius, just to test the program: therefore, the results are probably not realistic.
In output we get, for the values typed in input, the "gear #" needed for the various distances (some distances are negative: why?) and the "lens extension" (from film plane, I suppose...; isn't it? can anybody clarify this point? ).
Roughly judging by this rough test, the program seems well working, but needs some explanation/clarification for the above points.
And I confirm my opinion: the program deserves to be included in the IAPP website in the "Cirkut section".
Thanks for your help ! The discussion could look like "pure academy", but the Cirkut camera and the underlying "philosophy" (and technology) are a very important development in the history of photography.

Roberto.