Method used in many non-digital recce cameras going way back. Depending on speed, altitude, etc, BOTH the slit and the film move in a dance that realizes a long strip of exposed film. Sometimes the slit moves with but slower than the film, sometimes the slit may move opposite the direction of the film. Depends on the parameters mentioned above.
Developed as a replacement for the cameras with vacuum platens that would hold the film, while the platen moved in the camera (opposite to the direction of flight) to allow sufficient light to expose the film while the ground was moving by under the plane. Then sweealthuk on to the next frame. Happened real fast. While serving, I learned (had to) the intricacies of the NCCS-4 system. (Navy Camera Control System - 4th gen). The pilot turned thumb wheels on the stick (jets man) to set the altitude, air speed, and another parameter I no longer can bring up. These inputs controlled a series of relays that chose voltages to send that set the rate of stepper motors in two boxes per camera station. Each box contained several of these stepper motors, connected to a lunch box sized train of stainless gears on shafts, which ultimately controlled the shutter speed, aperture, platen speed, or went platenless where the film just ran past the platen (focal plane) drawn by motors, also controlled by this system. Ain't analog wonderful? No, I don't have the schematics. Anymore. Post K-17, pre KH-12. if you know what I mean. On Oct 19, 2012, at 12:57 , Steven Desjardins wrote: > Good explanation. I missed the idea that the film was moving and not > the slit. I'm still having the beer. > > On Fri, Oct 19, 2012 at 3:50 PM, David Parsons <[email protected]> > wrote: >> The easiest way to explain it is to describe how the film version works. >> >> The camera has a vertical slit the height of the frame. The film >> moves horizontally past the slit. Anything that is not moving will >> read as a streak, because from the film's perspective, it's always in >> the same position as the film moves. >> >> Anything that is moving is only recorded as it passes in front of the slit. >> >> For racing, it's used to see who passes the finish line first. The >> first person to cross is clearly shown, and each successive person to >> cross in front of the slit records farther to the side of the frame. >> >> I don't know how the digital version works, maybe a strip sensor that >> is sampled many times per second and composited in-camera. I wonder >> if it wouldn't be possible to do something like this for normal >> cameras and smartphones. >> >> It's really quite ingenious, and when you use it as an art tool, you >> get some striking imagery. The man and horses is my favorite of the >> set. > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
