By way of introduction to this article I will quote the question that prompted me to write it. The question was: "How does one set-up and use a Cirkut camera to make "linear strip photographs" of a passing train resulting in a long photograph presumably showing the train from engine to caboose including several cars in between?."
Now the answer or solution to the above question has been solved many individual photographers but possibly a step by step guide might still be useful for those struggling with this problem and in this spirit such a guide is given below.
The basic requirement or modification that needs to be made to any rotating panoramic camera to enable it to be used for "linear" applications is to devise some means for holding the camera body still while not impeding the motion of the film through the camera.
With Cirkut-type cameras this is not a big problem. Simply leave the geartrain equipped tripod head off the camera and attach the camera body directly to a tripod or make a cradle of some sort to hold the body while still allowing the fan or electric motor to transport the film through the back.
With other cameras the process is more or less complicated but the idea is still the same. I made a cradle for a Hulcherama camera such that when the camera is riding in it the tripod head rotates independently and freely within a depression built into the base. Although no absolutely necessary, the camera needs yet another "modification" for easy use in these "experimental" modes. This is the addition of an external on-off switch in a parallel configuration to the on-off swith located in the tripod head. This is not a very difficult thing to do but I suggest a handy electrician/mechanic install it for you if you are not so gifted! The circuit is easily seen and analyzed by removing the camera's bottom cover. This exposes all the electronic controls and it is a simple matter to follow the leads that go to the rotating tripod mount and install a parallel switch on the "control" panel on the camera. I simply added a 1.8mm micro jack to a "bare" spot on the control panel and made myself an extension with a micro plug at one end and a on-off switch at the other end.
Once modification is completed and the cradle is constructed the next item is to to calibrate the camera to determine how fast the film moves through it at various numbered settings on the Hulcher or when using a particular gear and a particular fan or at a particular voltage if using a powered model.
With a Cirkut you only really need to calibrate the camera with one "average" gear or setting knowing that you can easily double or halve the film speed by proper changes in the gearing or voltage ... fan may be less predicatable.
Anyway, with a Cirkut with separate back and front components you need only the motorized back, otherwise simply keep the camera off the pivot or the Hulcher in its cradle. Now load with film (scrap) and operate at chosen (or various) settings. To determine the rate at which the film moves in the camera you can proceed various ways. With a Cirkut you may be able to reach in through the slot from the front and with a marker place a mark onto the passing film and let's say 10 seconds later, place another, and so on.
Eventually you then look at the film and measure the distance between marks (this will change slightly since the take-up drum diameter changes as film builds up on it). With the Hulcher you do essentially the same thing. Just operate the camera with the top cover off and place a mark onto the passing paper every 10 seconds. From this then you can figure out the amount of film that passes by in 10 seconds and thus also the film speed on a per second basis:
Film Rate of Motion ("/sec) = amount film between marks/10 seconds
Or, with a Cirkut, if you have an indicator visible that tells you that the take up drum has made a revolution, you simply need to time how long it takes the drum to make one (or more) full turn. Then, estimating the diameter of the take-up drum and multiplying time 3.14 you get its circumference and thus determine that the average rate of film motion through he camera is:
Film Rate of Motion ("/sec) = Circumference of Drum/time for 1 drum turn
Let's say for the sake of argument that the film moves at 1 inch per second. Now if you have an exposure slot (measure it!) that is about 1/4 inch wide it would deliver an exposure time of 1/4 second. This is determined from:
Exposure time in seconds = slot size/rate of film motion
With the Hulcher the slot will be much smaller but you don't need to make this determination anyway since the camera has attached to it a table that provides the exposure time associated with any given choice of slit size and camera rotation speed.
Now eventually you will be taking the camera out to make your photograph. Assuming that the train will be moving at 10 miles per hour, you'd best translate this to feet/sec by multiplying mph times 1.5 (rough conversion). So, in this case the subject is moving 15 feet per second.
The moving image of the train's image at the slot is controlled by Magnification but in our case Reduction is a more appropriate term. That is, the image moves as many times slower than the real train as the size of the real train is compared to the size of the image of the train on your groundglass.
So, if you are using a given lens and the image of a train's feature which in reality is 10 feet tall gets reproduced at your groundglass as a distance of about 1" it means you are talking about a reduction of about 120 times thus:
Reduction = Subject size/Image size in this case 10 feet or 120"/1" = 120x
Another way to approximately determine Reduction is this (using same units):
Reduction = Distance from lens to train/focal length of camera lens
OK, now what to do. Well, since the train will be traveling at 15 feet per second, this is 15x12 or 180 inches per second. At the distance you happen to be at this will therefore will give an _image_ speed of the train which is:
Train Image Rate of Motion = Real Train Rate divided by Reduction
or, in this case:
Image Rate = 180"/sec divided by 120 = 1.5 inches/sec
But you know that with the particular gearing or whatever you have, the camera moves the film at 1" per second which is too slow. You have several options now.
1. You can find/determine what kind of gearing adjustment you need to make to make the film move faster ... smaller fan, higher voltage or appropriate adjustment in gearing. This will also reduce the exposure time since that will now be 1/4 inch divided by 1.5 inches/sec. or about 1/6th second.
2. You can change the focal length of the camera's lens to one which is 2/3 the original focal length. This will make the image of the train a bit smaller (in fact reduce its size to 66% original) Since reduction is greater than before the image moves slower. To figure out the factor by which you need to multiply the focal length of the lens you have on the camera to determine the focal length of the new lens you do this:
New Focal Length = Old Focal Length x Available Film Rate/Given Image Rate
From this you can see that if the film rate you "have" is equal to the image rate you "have", then the lens focal length you "have" is just the right focal length. Otherwise you take the focal length you have and "adjust" it as shown above.
3. You could also simply change the position of the camera and move it father away (in this case). The new distance should be 1.5 times further away from the train than the distance that the camera was from the train at the time you determined the rate of its image motion. Essentially this has the same effect as changing the focal length and you make the image smaller and thus it moves slower as well.
New Camera Position=Old Camera Position x Available Film Rate/Given Film Rate
One other item of importance is that you should make sure the train is moving from right to left in front of the camera as I believe inside a Cirkut camera the film moves from left to right. The optics reverses image motion and thus both the image of the moving train and the motion of the film will be in the same direction. However, in a Hulcher the film moves from right to left and with this camera the train should be moving from left to right.
Now you just load your camera, adjust the aperture for ambient conditions and film speed and wait for train to approach. As it gets close to the location on the track that the slot on your camera is aimed at you star 'er up and wait for the film to run out and then you process it and exclaim: WOW!
I hope this little "guide" that explains some of the logic behind the various operations is of help to you. As an additional thought, you might also experiment with placing the camera in a moving vehicle and while driving along a street flanked by picturesque buildings photograph a long stretch of the facades along one side of the street. The process for making this photograph is very much the same as that of making the picture of the moving train except for the fact that you would be moving instead of the train! Do not hesitate to contact me if any part of the is not clear or if you'd like additional assistance of any kind. I also look forward to hearing of a complete success story!
If you would like to discuss this project with me I would be happy to provide whatever assistance is needed. Contact me at RIT, PO box 9887, Rochester, NY 14623. Phone 716-475-2592, fax 716-475-5804 ... but the fastest way is to just send me e-mail at firstname.lastname@example.org