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#71
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"The exposures are at 1/100,000,000ths of a second"
Colin D wrote:
theres a corollary to this effect as well. Although the per-pixel - or per grain - exposure is 1/12000 sec, the total traverse time is quite slow, about 1/500 or less, as you say. If you are photographing a fast-moving object across the field of the camera, the object will have moved some distance during the shutter traverse, so although the details might be sharp, the image is time-shifted, causing vertical objects to be slanted in the image. Back in the days of the 5x4 Speed Graphic and similar cameras (with focal-plane shutter traverse time of about 1/20 sec), shots of racing cars would often show elliptical wheels and/or leaning-over power poles, depending on how the photog panned the shot. Even at 1/200 a propeller will be "bent". -- -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. |
#72
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"The exposures are at 1/100,000,000ths of a second"
In article , Alan Browne
writes Rich wrote: They could synchronize machine guns so they didn't blow the propellers off fighters in WW2, so making a multi slit camera mechanism should be simple. The first synchonizers existed in WW I Prior to that they had propellers with steel deflectors attached to simply bounce the bullet away from the prop. The British (and possibly US) air forces used a hydraulic interrupter design* by a Romanian gentleman by the name of Constantinesco. He had to wait until several years after the war to get any payment (a few tens of thousands) from the UK government, which they then proceeded to tax. He took a tax appeal to the House of Lords, and lost. I imagine he must have lost most of the money in this process. Still, it beats the few pence a day most British servicemen got at the time. *The firing of the machine gun was synchronised by a hydraulic impulse from the engine, synchronised so that it fired at the right time to miss both blades. The design of an interrupter for a machine gun firing at 600rpm (i.e. 10 rounds a second) is however a good deal different from designing a shutter for a 10^-8 second exposure. David -- David Littlewood |
#73
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"The exposures are at 1/100,000,000ths of a second"
In article , Rich
writes They could synchronize machine guns so they didn't blow the propellers off fighters in WW2, so making a multi slit camera mechanism should be simple. Even flat out, WW1 & 2 propellors moved many orders of magnitude slower than atomic fireballs. ;-) -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
#74
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"The exposures are at 1/100,000,000ths of a second"
In article , Alan Browne
writes Kennedy McEwen wrote: In article , Alan Browne writes My Maxxum 9 has a mechanical shutter speed of 1/12,000 of a second. Only 83 times slower than 1/1,000,000. It is a moving slit of the curtains in the camera. But the slit takes about 1/250th sec to traverse the entire frame. The fireball would be out by the time the first exposure was complete! :-( Similar problem with the idea of the slit in a rotating disk, although with a big enough disk the slit could be larger than the frame size. It isn't just the exposure time that has to occur in 1/millionth of a sec, it is the exposure of the entire frame. Somebody else beat ya to it. It happens. As do propagation delays getting posts from one server to another. From what I can see, the above post was made at least 2hrs before any other addressing problem. -- Kennedy Yes, Socrates himself is particularly missed; A lovely little thinker, but a bugger when he's ****ed. Python Philosophers (replace 'nospam' with 'kennedym' when replying) |
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