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Post by JayUtah on Jul 22, 2009 16:11:07 GMT -4
Yep. That's why I asked about the original frame rate of the camera. Lots of codecs play fast and loose with that sort of thing and standards conversion can be a real headache. The camera is field-sequential so it's hard to talk about frame rate without expounding all the details. The signals did at one time end up in a standard NTSC format for broadcast, but that doesn't mean the recording was made from those signals. The problem you typically run into is when a kinescope is somewhere in the workflow. Not all kinescope frame-rate conversions were strictly kosher. Further you have spatial changes to deal with. Small changes in aspect ratio in the conversion workflow can wreak havoc on spatial information extracted from the video. You must first typically rectify that problem before starting to talk about measuring pixels. In short, anyone who shows up with downloaded convenience video as data is in for a rough ride.
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Post by drewid on Jul 22, 2009 16:15:17 GMT -4
Also was there any standards conversion going on bewteen transmission and it being recorded, as with the Australian bounce of the Apollo 11 landing? Aspect ratios and frame rates: bane of my life, but in this case it shouldn't be too bad, the hammer stays pretty vertical, and I'm only measuring the vertical and using the known hammer length as a datum, and I did say it was rough.
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Post by blackstar on Jul 22, 2009 16:29:46 GMT -4
Something that occurred to me earlier is that we are watching a feather and a hammer dropping at the same speed in a vacuum in a gravity field that allowing for the rough quality of the video is 1/6th g; if it isn't a video from the moon what the heck is it! If you are going to argue that the errors and approximations that are bound to creep in when working with web video as a source mean something shouldn't you propose a viable alternative for people to weigh in the balance of evidence?
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Post by BertL on Jul 22, 2009 16:30:55 GMT -4
BertL, sorry to disappoint you, but at 1:00.96 the handle of the hammer finally lays on the ground, the hammer head hits the ground first before that. ;D You should stop at the frame when the hammer head touches the ground, not when the entire hammer lays on the ground. Hmm, you're actually right. The hammer hits the ground already on frame 1822 (at 1:00.79 into the video). This works out to a 1.17 seconds time of free fall, or 1.10 meters. (Incidentally, the hammer's handle doesn't touch the ground until 1865, which is about 1.4 seconds later.) Drewid's measurements are particularly interesting, as they seem to indicate that contrarily to what our eyes tell us, the hammer does fall only 120 centimeter.
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Post by drewid on Jul 22, 2009 16:50:28 GMT -4
120-130 so that's 47" to 51" ish. Now I'm 5"8 and not wearing space boots, but that's about nipple height, so is consistent with where his hands are.
edited for clarity.
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Post by johnsmith on Jul 22, 2009 17:01:09 GMT -4
The hammer head reaches the ground at 1:00:24. Shall we agree on this? It is pretty obvious, as the hammer image stabilizes on the ground from 1:00:24 to 1:00:26 as a result of the collision and then the handle starts inclining towards the side of the camera.
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jul 22, 2009 17:05:18 GMT -4
Drewid's measurements are particularly interesting, as they seem to indicate that contrarily to what our eyes tell us, the hammer does fall only 120 centimeter. Your eyes, maybe ... I don't care if it's posted on a NASA website or not, the height estimate of 1.6 m is clearly not right. The hammer head is no higher than Scott's mid-torso. I'd estimate it to be maybe 1.1 to 1.2 meters, certainly not 1.5 or 1.6.
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Post by drewid on Jul 22, 2009 17:22:26 GMT -4
(That's my nipples of course, your mileage may vary)
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Post by BertL on Jul 22, 2009 17:24:08 GMT -4
The hammer head reaches the ground at 1:00:24. Shall we agree on this? It is pretty obvious, as the hammer image stabilizes on the ground from 1:00:24 to 1:00:26 as a result of the collision and then the handle starts inclining towards the side of the camera. Sorry I keep arguing against this John, but 1:00:24 and 1:00:26, at the 29.97FPS framerate of the video, translate to frames 1805 and 1806 (roughly). Here are those two frames, in fullscreen glory (big images ahead). Frame 1805Frame 1806You can clearly see the hammer (and feather) are still in mid-air in these frames. Now, if we take a look at frames 1820 to 1823 in this short animation: ( Here is full resolution version of the animation.) You can see the hammer still falling in 1820 and 1821, then coming to a standstill in 1822 and 1823. This translates to an ending time of 1:00.79. One thing that might cause our times to be different is an out-of-sync problem my software might be having with the .mov file. Perhaps we should compare the time the hammer start falling as well, to check this. Drewid, how did you find out the hammer is 39 centimeters long? I've read the number on other websites before, but I never really found out where the number came from.
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Post by drewid on Jul 22, 2009 17:38:10 GMT -4
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Post by johnsmith on Jul 22, 2009 18:00:39 GMT -4
The hammer starts moving down slowly at 0:59:14, the astronaut seems to be holding it partially. This continues till 0:59:16. After that the hammer quickly starts falling down and reaches the ground at 1:00:24. So, for the two alternative starting times:
1) 1:00:24 - 0:59:14 = 1.1 s ; d = [1.63 x (1.1)^2] / 2 = 0.986 m
2) 1:00:24 - 0:59:16 = 1.08 s ; d = [1.63 x (1.08)^2] / 2 = 0.933 m
Ulead VideoStudio calculates the time automatically.
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Post by johnsmith on Jul 22, 2009 18:18:43 GMT -4
File File Name: AS15_Ham_feath_drop3.mov File Format: Quicklime Movie Files Movie size: 720 x 480 Duration: 82.816 seconds Track counts: 1 video track(s), 1 sound track(s)
Video Track 1 Compression: Sorenson Video 3 Attributes: 24 bits, 720 x 480 Total frames: 2,482 frame(s) Frame rate: 29.970 frames/sec Duration: 82.816 seconds Start at: 0.000 seconds
Sound Track 1 Compression: 16-bit Big Endian Attributes: 44.100 KHz, 16 bits, Stereo Total samples: 3,652,178 samples Duration: 82.816 seconds Start at: 0.000 seconds
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Post by JayUtah on Jul 22, 2009 20:28:04 GMT -4
Ulead VideoStudio calculates the time automatically. Based on what data?
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Post by JayUtah on Jul 22, 2009 20:37:00 GMT -4
That's the output of the encoding process. What was the input?
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Post by johnsmith on Jul 23, 2009 0:12:08 GMT -4
Good question. If I knew, I would not open this thread. People participate in forums because they do not know all the answers. It is a part of a process called truth seeking.
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