GB2337130A

GB2337130A - Flicker free cinema system

Info

Publication number: GB2337130A
Application number: GB9809614A
Authority: GB
Inventors: John Eric Dowell
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-05-07
Filing date: 1998-05-07
Publication date: 1999-11-10
Also published as: GB9809614D0

Abstract

A system is disclosed for photographing moving objects and to the projection of images produced onto a screen so that they appear to be flicker free. The system comprises two cine cameras, each having exposure systems with synchronised shutters, which can preferably take alternate exposures of a scene on different films. The system also comprises two projection systems for projecting the films produced by the cameras.

Description

2337130 FLICKER FREE CNEMA SYSTEM This invention relates to the

photographing of moving objects and to the projecting of images on to a screen so that they appear to be moving.

Cinema methods show stroboscopic effects in which wheels on moving cars or wagons stand still or go backwards. Older and amateur systems use 18 frames per second or less and have a visible flicker. Professional projection is done at 24 frames per second, which reduces the flickering effect, but may cause eye strain or lead to headaches.

In this invention two reels are used with two cine-cameras or two projectors such that while one film is exposing, the other film is moving to the next frame, then, as one film's shutter closes the other film's shutter opens up.

Specific embodiments of the invention will now be described by way of examples, with reference to the accompanying drawings in which:- Figure 1 shows the main features of exposing and moving the films. Comparing the Reel A System exposure with the Reel B System exposure on a time base. So essentially there is continuous exposure. The usual system of move and expose is shown at C for comparison purposes.

Figure 2 shows a possible arrangement of the cine-cameras or of the projectors. To reduce distortion, the Optical Axis of the two systems are kept close together, while still getting the most light through.

Figure 3 shows a cassette method of keeping the two films synchronised.

Figure 4 shows a film format for use with the cassette.

Referring to the drawings. In Fig 1, the level 12 shows the shutter fully open, the slope 13 shows the shutter closing down, the slope 15 shows the shutter opening and 14 shows the film advancing with the shutter closed. As 13 closes down in A so 15 opens up in B, then as 15 opens up in A so 13 closes down in B, thus keeping the amount of light constant, and there is a blend between the two frames In Fig 2 a method of implementing the invention for large format film is shown. Typically for a camera, a pair of mirrors, 21, deflect light rays. 23 is such a light ray (shown dot-dashed) and is on the optical axis of the upper system, but is above the apex of the mirrors. 24 is a light ray that is on to the optical axis of the lower system, but is below the apex of the mirrors. 25 represents the reels and film for the upper system with 27 representing the iris, lenses and shutter for that system. Similarly 26 represents the reels and film with 28 the iris, lenses and shutter for the lower system.

The blinders, 22, are to keep out stray light; they are directly attached to the mirrors 21 which can move out (to the left) or in (to the right). When the mirrors are fully in, the rays 23 and 24 coincide with the apex of the mirrors. Due to the lack of mirror and to the blinders the left half of the lenses will receive no light. The film then only gets half the lumens otherwise expected. As the mirrors move out to the left the rays 23 and 24 separate, the lens become more uncovered and more lumens get to the film. When fully out the film gets all the lumens, but the rays, 23 and 24, are well separated and will give different pictures which effect objects at different distances from the camera.

The projector is similar but has lights, and projects on to a vertical surface. If the mirrors are out then the rays 23 and 24 are far apart, and adjustments must be made for rays 23 and 24 to converge at the centre of the screen. A point at the bottom of the screen is closer to the lower system than to the upper system, so an image from the upper system will appear below the corresponding image from the lower system. This difference increases with the distance from the centre, but as frames are wider than their height, then a vertical arrangement, as shown, is best. Then horizontally there is no distortion.

Fig 3 shows a cassette system for use with smaller formats. Starting at 3 1, this is the twin reel with one tape above the other. Sprocket 32 keeps the tapes synchronized. Block 33 reads the sound tracks and other information. Sprocket 34 draws the tapes from the cassette at a steady rate, keeps the tapes synchronized and feeds them to a loop. Sprockets 35 combine to alternatively feed the upper and the lower film tapes to a place behind the lens, for exposure in a camera or display in a projector. The sprocket 36 controls the output loop and feeds the tape back to the casette at a steady rate. Sprocket 37 keeps the tapes synchronized and feed the twin reel take-up spools 38, which are driven as one single reel.

Fig 4 shows the tapes as they emerge from the casette. The holes at 41 are to enable the Sprockets to keep the tapes synchronized and in place. The photographic area is at 42 and the upper and lower areas are kept close together to help to reduce distortion. The tracks at 43 are for the sound system. The track at 44 is for film information.

Claims

1. Two reels are used with two cine-cameras or two projectors such that while one film is exposing, the other film is moving to the next frame, then as one film's shutter closes the other film's shutter opens up.

2. A cassette as claimed in Claim 1 wherein each of the two tapes used therein has a format where the sprocket track is near the middle of the tape, the pictures are on the inside to be close to the pictures on the other tape, and the sound and information tracks on the other side of the sprocket track.

2. A system of two cine-cameras linked so that when one is moving its film the other is being exposed, then the time and shape of the exposure can be adjusted to suit light conditions and movement.

3. Twin reels of film where one reel has the odd numbered frames and the other the even numbered frames, then the reels have to be shown alternatively to produce the desired effect of smooth motion.

4 Conversion of Twin reels to a single reel system.

5. Conversion of a single reel to Twin reels.

6. Putting markings on the Twin reel film so that the projector can read the sequence of the frames.

7. Putting markings on the Twin reel film so that the projector can read the speed in frames per second that it should be operating at that time, which may vary during the film showing.

8. The arrangement of a pair of mirrors with the cameras or projectors to provide more light until distortions become distracting.

9. A cassette to keep the tapes of twin reels synchronised.

10. A tape format with the sprocket track near the middle, the pictures on one side and the sound and information tracks on the other side of the sprocket track.

r - (D - Amendments to the claims have been filed as follows 1. A cassette to keep the tapes of twin reels synchronised, comprising a box enclosing two ready reels on one axis, a sprocket to feed the tapes out in synchronisation, a cut out to enable the tapes to be pulled out and threaded through the camera or projector, a second synchronising sprocket and a pair of take up reels locked on to a driven axis.