Welcome to my Panoptic Camera Page

Garson, Ontario, Canada. 13 Dec 1996 exp: 1/60 f/8-11, tri-x film rated 320 asa.

A recent interest is the panoptic camera. This camera is designed to make an image 360'. They are capable of making some fantastic images, particularly when slow shutter (camera rotation) are used and also when the camera is not perfectly level.

In general these camera are mounted on a tripod and leveled. The camera then rotates part of or the full 360 or more degrees. The shutter is opened at the start of rotation and closed at the end. The image from the lens is passed through a slit in the back of the camera onto the film which is being wound up on the take up spool. There are a number of considerations when designing this camera.

There are some basic math calculations that have to be done. I would like to use 120 roll film and the image length should be 176 mm long

  • The basic formula at the heart of the camera is 2 * focal length of the lens. I don't know where this formula originated nor can I explain it.

    For example if a 80mm lens were to be used the length of the image would be

    80 x 2 = 160 x 3.1416 = 502.6 mm, only contact prints could be made from this image

    For my example, my enlarger can handle 176mm long negative. To determine what length of lens is required.

    176/2 = 88, 88/3.1416 = 28mm focal length.

    Which is great for me since it is the only wide angle lens that I own, also there is more vertical coverage with a shorter lens. I should mention that my Cannon 28mm lens actually focuses at 35mm from the rear flange. This will be important later in the construction of the film box. This 35mm lens is designed to cover a 24 x 36mm rectangle with a diagional of about 43mm. This lens will not cover the 120 film, however it only has to cover the slit which is 1mm wide and about 53mm high. The Cannon lens will cover about 90% of the height.

    You will notice the small piece of wood on the back of the lens. It is wedged lightly between the aperature control pin and the maximum aperature pin. Doing this will allow the aperature to be set on the lens barrel

  • As the camera swings in a 360' circle, the film is pulled past a slit were it is exposed to the image created by the lens. The total exposure of the length of image is

    176/width of slit = 176/1 = 176 x 1/30 = 5.9 sec.

  • Now that the time is known, determine rpm of the camera ( 1 rev in this time period)

    60/5.9 = 10.2 rpm

  • Find out how many revolutions of the take up spool are required for the given length of image

    Note: the diameter of the 120 film at the start of each of the 4 exposures is 15, 17,19 and 21mm. I chose to use the 19mm diameter as an average for the entire film length. 1 revolution of the take-up-spool is

    19 x 3.1416 = 60mm.

    The number of revolutions required to cover the length of image (176) is

    176 / 60 = 2.9

  • The speed of the t-u-s is equal to the total time of exposure (5.9 sec) divided by the revolution of the spool (2.9) is

    5.9 / 2.9 = 2, rpm = 60 / 2 = 30

  • Now to bring all this together, the camera makes 1 revolution in 5.9 seconds. While the camera is rotating the film is being wound by the slit at the rate of 176mm in 5.9 seconds. All the above calculations will be used in the next step, that is to make a drive system with a small d.c. motor.

    The motor that I have used is made by Fauhlaber Schonaich, supplied by Micro Mo Electronics (they are sending me a catalog, this motor has been replaced by #2034b @ $71.45). The motor operates at 4.5 volts dc, with the speed control it has a speed of about 325 rpm. I used a round file to put a groove in the brass gear to acecpt an o-ring. The diameter of the groove is 7mm, it drives a pulley that has a diameter of 49mm (46.6 rpm). On the same shaft is a small pulley 7mm diameter, it drives a pulley with a diameter of 32mm (10.2 rpm, the camera rpm).

    The take-up-spool is rotated at the bottom by a pulley, inside the wood are two #r4-2rs bearings (6mmx20mm $8 each). I tried to use a brass sleeve however it tend to bind from the pressure of the o-ring. (sorry about the fuzzy image I do not seem to be able to make it sharper)

    Mounted on the motor drive base is a pulley that has a diameter of 40mm. Since the camera rotates on a fixed base, the film is wound up using this fixed pulley; it drives a pulley connected to the t-u-s with a diameter of 13.8mm (30 rpm).

    The speed control from an ECG book, this device is a 3 terminal voltage regulator ECG 956. The basic configeration uses a 5k trim pot to control the output voltage. By replacing the single trim pot with several trim pots and a multi-position switch. Each position of the switch will represent a different voltage and therefor a different shutter speed(rotation). The other advantage is that as the battery voltage drops the camera speed will stay constant until the battery voltage falls to a level the 956 can not handle. At this time a new set of batteries is required or recharged which ever is the case.
    Thanks for visiting this page, if you have any questions please send E-Mail