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THE PRINCIPLE OF THE LOOKAROUND CAMERA. The camera turns freely on its axis at all times. The weights are the motor. They act as a flywheel and stabilizer. The camera exposes the film similarly to a conventional focal plane shutter camera. The difference is that the camera and the film move instead of the shutter slit. The length of film per rotation is governed by the take-up disk (it has the same radius as the lens focal-length). The main exposure variables are rotation speed (equivalent to shutter speed) and aperture. The width of the slit introduces a third variable to the effective exposure. The key exposure concern with rotating cameras is that a maximum range of brightness values in a scene is unavoidable because the camera turns into and away from the light. The speed of rotation/slit-width give an effective shutter speed value. For example using the 24mm lens, with full sun, using 400 ISO film the aperture is set at f11 and the camera spun at about one-half to three-quarter rotations every second. This gives an effective exposure of about 1/500 sec.@f11. The shutter speed of focal plane or slit shutters is the local speed of the width of the slit past an equal segment of the film. It takes more time for the film to pass by a wider slit even though the camera is turning at the same rate, thus allowing more motion blur. While learning, you should spin the camera and use a digital watch to estimate the rotation speed. You can easily compare a half rotation with one second intervals. In regard to effective shutter speed consider this: if the camera slows down to half its optimal speed it is only decreasing exposure by one stop. It is quite apparent when the camera slows down or speeds up by a factor of one stop. The mass and radius of the weights are designed to turn the camera nicely at about one-half to three-quarter revolution a second and pull the film at an even rate. You will have no trouble knowing if the camera is spinning correctly after a few tries. Slit to film distance. In practice you don't need to change the distance the slit holder is from the film when using one type of film. You can move the slit closer to the film if you are using non- perforated films. This gives better sharpness and motion stopping because the slit can be proportionately narrower. If motion is not a factor it is better to leave the slit away from the film. Perforated film doesn't exit the cassette as smoothly and must be further away from the slit. The flexible design of the Lookaround slit is meant to give the experienced user a great deal more creative control than is available on other cameras. Slit width. The slit width obviously has to change the amount of light that reaches the film. The slit also effects the evenness and sharpness (motion blur) of the image in the same way as a slow shutter speed effects a conventional camera image. There are trade-offs involved. The wider the slit and/or the further away the slit is from the film, the less un-even film movement appears in the image (vertical bands of varying density). The trade-off is that you may get more subject motion blur. With a very wide slit, camera movement (other than the rotation) may also cause blur. You can use a wide slit in low light but subject motion will be blurred. The difference in exposure is about one stop each time you double or halve the slit width but you should test this yourself. Lens focal length. Increasing the focal length of the lens increases the length of the image. Therefore, more film has to pass past the slit at a given time. That means you have to give proportionately more exposure. It is likely that you will find that one setting of slit and speed exposure variables will work for most daylight situations, leaving only the aperture adjustment to consider. The Lookaround Camera How Sharp are the Images? Digital Darkroom Notes Build a Lookaround Panoramic Enlarger LOOKAROUND HOME PAGE |