John Dolva Posted February 7, 2009 Author Share Posted February 7, 2009 (edited) The Education Forum > Controversial Issues in History > JFK Assassination Debate 30 Pages « < 28 29 30 Jump to Page Missing Nix frames - in an endeavour that developed into a work in progress around the synchronisation of Film and Photo's relevant to the Assassination. rc This is an interesting idea John, I have read about computer models which can calculate the suns position in the sky relative to an observer, for any location and date (including the creation of sunlight and shadow patterns). This sort of thing is often used in automobile accident investigations when a driver claims that he was blinded by the sun or that a pedestrian stepped out from a area of deep shadow... It is also used in building design to show the impact a building will have on neighbouring buildings in terms of shadows cast, etc... The unknown for me would be the relative degree of accuracy...will this be accurate within 1 second or 10 seconds, and if so, can we then rely upon the benchmark used for the recorded times for the Hertz sign, the timings of the descent to the 1st floor, etc, etc...in relation to this calculation of 'sun' time as it were. jd Thirdly, I hypothesise that a great deal of accuracy can be achieved as far as frame rate reduction goes by delving deeper into some matters. Apart from what you correctly (IMO) say re. unwind rates, there may be other approaches as well, for example you may remember my odd postings re deducing the speed of an object in relation to camera movement, static background, object movement, from an analysis of the various blurs and knowing the exposure time, form a SINGLE frame or photo. Also, the wheels of the Limo has a specific dameter, and if one can identify any point on this wheel and deducing how far it has moved in an arc during the frame exosure then one may have a very accurate speed. I wonder to what extent, if any, the windown, framerate in anyway changes the exposure rate. I imagine that it is a good idea to have it built so that the frame rate mechanism trips a frame shutter opening time that remains to all intents and purposes constant. fa You may be on to something here... I need to ponder a bit on what you've written, but I find the ideas intriguing. Thinking out loud for a moment: Motion blur is tricky, because we don't have all three axis of motion available to us. Rotation might prove to be more revealing. Also -- we need to look for variances in the shutter speed as well as the frame rate. Frame rate has been used to "timestamp" the events. Time also passed while the frame was held open. I'm sure there is some variability to this -- after all, it is a mechanical contraption at work. It may, however, be more regular than frame rate. I don't know if anyone has researched this aspect of the film cameras involved... (my italics, let's see) jd The three axis issue may not be as elusive as you reasonably suggest. Back to it later. _ What's your thoughts on this (musings derived from a tangent of the convo Craig and I were having yesterday) : In the Towner film there is an excised frame. If one looks at the preceding and following frames one sees a reflection that increases in luminosity and then decreases and it seems reasonable to me to assume that this frame was excised because at that moment in time the sun (which is in a known, particular position at any time, anywhere) overexposed the frame. Therefore using standard astronomical, survey, navigational techniques one may be able to say exactly, perhaps even to the second (give or take a reasonable error margin) when that frame was exposed. Then the implications are enormous. Just think about it. Exactly what time lets say 12.33 is. 12.33? is it 12.33.01 or 12.33.59?. Step that through the timing of events such as the time it takes to get to the lower floor issue, or in this case use it as a bencmark to step through all synched films??? The factors to consider is trangulations to determine the exact position of the film surface at that moment, the exact position of the Limo, and then working out where the sun must have been. Then a reference to the appropriate sun tables... Could this be the primera? cl I think the biggest problem, John, is that reflections are tricky things. They change rapidly, even with a constant light source in both position and intensity, with even the slightest movement of camera or subject positon. As a studio photographer for decades, tasked with creating perhaps millions of lighting schemes, I have seen this effect countless times. Its that old angle of incidence thing. You have an interesting concept, but perhaps with many perils. jd Thank you. I can see the problems re the reflective surface. However, while it's there it is also a potential knowable as this is a manufactured vehicle with specs. In a sense, at that particular frame, T.Towner is taking a snapshot of the sun, which is another knowable re time angle et,c.. The vehicle can be located and orientated using the west survey, the location of the lens/film can be located. The point of reflection can firstly be located roughly, then knowing that the vehicle has specs re surface shapes one can deduce, probably within a fairly small area, the actual p.o.r. . Then one has to judge the error margins involved and see whether it is possible to get to something that could then be useful as 'some seconds + or - error margin'. And then know the Time. Convoluted yes, difficult yes, impossible, I don't know, quite possibly so. The shadow idea as described by Russ (thank you) depends also on some possibly knowables like height of a lamp post, its elevation and the distance from the base of it its centre at the base to where the tips shadow strikes the ground, the elevation of the ground at that point. How plumb is the object that casts a shadow? These are possible knowables and again with error margins considered may yield sub minute readings. Good ideas. However from there to a useful result won't necessarily be easy, but (I think) worth pondering. One thing about using a single frame of one of the known films, and getting a correct reading, is that it then can bypass many other issues and skip through and across the films and photos and reveal many apparently unrelated things and more obvious ones. At the moment, I think, it's a matter of identifying the most problematic and subject to error margins that takes the calculations into something useless. . Incidence angle may turn out to be just that problem. However, the fact remains that such a reflection or such a shadow could only have occured at one particular moment in time. Perhaps other thought will flow from this and trn out to be useful, wheereas the reflection frame may be too problematic. Though, I suppose, there are really no problems, just solutions hanging around waiting to be spotted. (thanks John Lennon r.i.p.) rc : This is an interesting idea John, I have read about computer models which can calculate the suns position in the sky relative to an observer, for any location and date (including the creation of sunlight and shadow patterns). This sort of thing is often used in automobile accident investigations when a driver claims that he was blinded by the sun or that a pedestrian stepped out from a area of deep shadow... It is also used in building design to show the impact a building will have on neighbouring buildings in terms of shadows cast, etc... The unknown for me would be the relative degree of accuracy...will this be accurate within 1 second or 10 seconds, and if so, can we then rely upon the benchmark used for the recorded times for the Hertz sign, the timings of the descent to the 1st floor, etc, etc...in relation to this calculation of 'sun' time as it were. cl I think the biggest problem, John, is that reflections are tricky things. They change rapidly, even with a constant light source in both position and intensity, with even the slightest movement of camera or subject positon. As a studio photographer for decades, tasked with creating perhaps millions of lighting schemes, I have seen this effect countless times. Its that old angle of incidence thing. You have an interesting concept, but perhaps with many perils. jd Thank you. I can see the problems re the reflective surface. However, while it's there it is also a potential knowable as this is a manufactured vehicle with specs. In a sense, at that particular frame, T.Towner is taking a snapshot of the sun, which is another knowable re time angle et,c.. The vehicle can be located and orientated using the west survey, the location of the lens/film can be located. The point of reflection can firstly be located roughly, then knowing that the vehicle has specs re surface shapes one can deduce, probably within a fairly small area, the actual p.o.r. . Then one has to judge the error margins involved and see whether it is possible to get to something that could then be useful as 'some seconds + or - error margin'. And then know the Time. Convoluted yes, difficult yes, impossible, I don't know, quite possibly so. The shadow idea as described by Russ (thank you) depends also on some possibly knowables like height of a lamp post, its elevation and the distance from the base of it its centre at the base to where the tips shadow strikes the ground, the elevation of the ground at that point. How plumb is the object that casts a shadow? These are possible knowables and again with error margins considered may yield sub minute readings. Good ideas. However from there to a useful result won't necessarily be easy, but (I think) worth pondering. One thing about using a single frame of one of the known films, and getting a correct reading, is that it then can bypass many other issues and skip through and across the films and photos and reveal many apparently unrelated things and more obvious ones. At the moment, I think, it's a matter of identifying the most problematic and subject to error margins that takes the calculations into something useless. . Incidence angle may turn out to be just that problem. However, the fact remains that such a reflection or such a shadow could only have occured at one particular moment in time. Perhaps other thought will flow from this and trn out to be useful, wheereas the reflection frame may be too problematic. Though, I suppose, there are really no problems, just solutions hanging around waiting to be spotted. (thanks John Lennon r.i.p.) cl John, as little as a few mm of camera movement can totally change the nature of a reflection, as can very slight changes in the lightsource, or the reflective material. I wish you well , but IMO at least, the process looks quite difficult and the possibility of error great. _________ jd What do we need to know in order to firgure out the distance a film frame in a camera is from an object in the field of view? If we have a known dimension of an object, say a window or the height of a lamp post, do we need to know the distance between the lens of the camera and the film, the lenss' characteristics and settings, etc to use the (can't remember the word for it, 'inverse square law? candlepower? I can't remember.) Anyway a line of sight and a known dimension might locate the photographer exactly? jd What do we need to know in order to firgure out the distance a film frame in a camera is from an object in the field of view? If we have a known dimension of an object, say a window or the height of a lamp post, do we need to know the distance between the lens of the camera and the film, the lenss' characteristics and settings, etc to use the (can't remember the word for it, 'inverse square law? candlepower? I can't remember.) Anyway a line of sight and a known dimension might locate the photographer exactly? jd What I'm trying to get at here, is ,that if one, in a perpendicular plane to the lens', can locate a knowable distance, height length, whatever, on two planes one can then have a unit relationship between those objects and how they measure on the photo itself, therefore one can know the distance between those two planes and deduce the distance from the film surface to the object. Thus, in Altgens 6 for example, one can, with an easily derived line of sight, measure from an object in a line of sight to Altgens exact position. (hypothesis) jd In this example of a uniform structure, (dimensions known, location known), how far is the camera from the red spot? What do you one need to know to calculate it? How exact will that calculation be? hyp_dist_test_01.jpg ( 68.49K ) Number of downloads: 5,400,495 ------------------------------------------------ - (Logging a post from another topic (with additions) : ( #191* , Feb 1 2009, 10:09 AM , The Gordon Arnold Illusion - ) A low res (400 odd k's from a 50+ meg file) example. http://educationforum.ipbhost.com/index.ph...st&id=16966 for follow ups, go to post # 191 * ( 451.64K ) Number of downloads: 8 With good copies to start with, so much more can be done. add : ( http://i27.photobucket.com/albums/c168/yanndee/b-1.gif http://i27.photobucket.com/albums/c168/yanndee/b.gif http://i27.photobucket.com/albums/c168/yanndee/c.gif high res survey : http://s27.photobucket.com/albums/c168/yan...P_ss_HSCA-1.jpg - click on 'full size' to download large copy The various composites (as per ''Missing Nix Frames' (with addendum in 'Tips') technique show movements of persons and objects as 'ghosts', and when they are more static the accumulation of data at a point is more intensified. (For example the movements of various running persons as 'ghosts' in the composites.). Mastering this technique allows for the creation of movie clips of a event from the view of a number of photographers. One takes the merged composite and places an unmegred copy on top of it, then hiding each frame in turn, saves frames that then can be combined in a movie maker utility. Finding a common point allows comparisons that may show anomalies. (apart from getting a better view of the sequence of events. One can, for example, set it looping in a viewer and study again and again certain areas.) --------------------------------------------------- jd The hope is that in this topic someone will do a calulation that can then be confirmed or not in order to work closer to a uniform concept where the variables needed are fully recognised and the measuring the distance between a photographer and an object can be universally applied. For the sake of science, two separate confirmations are OK, three is better. Then hopefully a standard fomula may be developed to use in any photo or frame. fa John This might help get the ball rolling: http://people.rit.edu/andpph/text-basic-photogrammetry.htm jd Frank, Photogrammetry is part of the 'picture' for sure. I think the first q is : where is the central z axis of the lens? Has the photo been cropped, (see the exif dta (re. image size)). Can anyone deduce the actual centre? jd Ok, the roughly 30 degrees bearers are 2 b'3s'. the planar structures are equal in size, plumb and 'equispaced'. The centre of the photo precropping is about 8.45 from the croppeds' centre. next.jpg ( 16.18K ) Number of downloads: 1 fa John, The more I think about this, the more I think this is a tough nut to crack. I think one thing that would be helpful -- that we probably don't have and may never have available -- are comparative photographs made with the same optics under controlled conditions. My lack of posts on this topic should not be interpreted as a lack of interest. At this point I've got more questions than answers; more variables than equations. To make matters worse, I'm a little rusty on a couple of related concepts that would probably be helpful here. As they say, I need to hit the books a bit. rc I have to concur with your view Frank...I have limited experience with photogrammetry but getting back to the topic point - any attempt to try and calculate with any degree of accuracy, the exact time (to the nearest 10 - 30secs) in November 1963 when the sun shone on a given surface (the Nix camera lens) will definitely introduce error margins which may render the effort redundant... What we know - to the nearest 60 secs or so - is when the shots where fired and when certain other events occurred ...but what we can't ever nail down, is the relative timings of said events to each other (i.e. the first shot, LHO exit from the TSBD, the time on the TSBD roof clock, LHO hailing taxi, etc, etc)... The accuracy we require is probably beyond us - for example, the earths orbit around the sun is not consistent and is subject to slight fluctuations which could introduce certain error margins which cannot be rounded down to a degree which can challenge currently proposed timings... fa Hi Russ, I think from some of our earlier work, we have established some good *relative* timings based on film sync. But as you pointed out, establishing exact (absolute) timings may be remarkably difficult. The first thing that came to mind when John mentioned reflections, etc, was to employ some ray tracing technology. jd Russ, good points to consider. Thank you. Frank could you explain 'ray tracing' in this context, please? --------------------------------------------------- Just logging : Lat: 32.7785570 Lon: -96.8082810 U.S. Naval Observatory Astronomical Applications Department Sun and Moon Data for One Day The following information is provided for Dealey Plaza, (longitude W96.8, latitude N32.8): (height above sea level ~ 415 feet) Friday 22 November 1963 Central Standard Time SUN Begin civil twilight 6:37 a.m. Sunrise 7:03 a.m. Sun transit 12:13 p.m. Sunset 5:23 p.m. End civil twilight 5:49 p.m. Dallas (longitude W97.3, latitude N33.3): Friday 22 November 1963 Universal Time - 6h SUN Begin civil twilight 06:40 Sunrise 07:07 Sun transit 12:15 Sunset 17:24 End civil twilight 17:51 ______________ designing a sun dial : http://www.mysundial.ca/tsp/lat_long.html ______________ graph of atmospheric refraction vs. elevation. : http://www.srrb.noaa.gov/highlights/sunrise/atmosrefr.gif ______________ Azimuth/Elevation/Zenith Figure. : http://www.srrb.noaa.gov/highlights/sunrise/azelzen.gif ______________ *Ascention, Declination Figure. : http://www.srrb.noaa.gov/highlights/sunrise/celsphere.gif ______________ Ecliptic Figure. : http://www.srrb.noaa.gov/highlights/sunrise/ecliptic.gif ______________ A sidereal day is slightly shorter than 24 hours (3 minutes 55.91 seconds shorter ______________ 40°N Boulder, CO, : http://www.srrb.noaa.gov/highlights/sunrise/fig5_40n.gif ______________ sample : http://www.srrb.noaa.gov/highlights/sunrise/azel.html sample.jpg ( 49.48K ) Number of downloads: 1 attachment What I'm getting at here is that the actual solar location and time, and as one is considering fractions of light tears a main (to all intents and purposes) paralell stream of photons from the sun hits the earth, a precise calculation for a location CAN be made. +++++++++++++ With regards to locating the distance from a photographer to an object in a photo, while initially daunting, may possibly, as many such things do, turn out to be simpler than one may think. Still, an objective comprehensive attitude is important and sometimes good comes out of the seemingly impossible. At the moment it's collecting all the variables and analysing them, ascribing them an error margin, then using the worst relevantb error margin to make a statement about whether it is of any value. That process is difficult. Once attained, it may be 'self evident'. jd It seems to me that there are three main issues with a number of sub issues Astronomic - essentially knowables The Image under scrutiny - largely likely knowables Lines of sight - knowables The Camera - largely likely knowables The formula may be complex, figuring it out may be so too. Once verified (if attainable) very precise and universally applicable. ???. Edited February 7, 2009 by John Dolva Link to comment Share on other sites More sharing options...
Russ Connelly Posted February 7, 2009 Share Posted February 7, 2009 +++++++++++++ With regards to locating the distance from a photographer to an object in a photo, while initially daunting, may possibly, as many such things do, turn out to be simpler than one may think. Still, an objective comprehensive attitude is important and sometimes good comes out of the seemingly impossible. At the moment it's collecting all the variables and analysing them, ascribing them an error margin, then using the worst relevantb error margin to make a statement about whether it is of any value. That process is difficult. Once attained, it may be 'self evident'.[/i][/size] jd It seems to me that there are three main issues with a number of sub issues Astronomic - essentially knowables The Image under scrutiny - largely likely knowables Lines of sight - knowables The Camera - largely likely knowables The formula may be complex, figuring it out may be so too. Once verified (if attainable) very precise and universally applicable. ???. +++++++++++++++ I agree that sometimes things are more simple than they seem and would endorse the view that potential problems should be tackled and explored rather than ignored. As you say, once verified, such data would be very precise and universally applicable. But to point out one example, in terms of solar calculations, the NOAA website states that its solar calculator is based on the algorithms of Jean Meeus which are accurate to within 1 minute for locations +/- 72 degrees latitude and within 10 minutes outside of these latitudes - these error margins being due to atmospheric conditions which are local and constantly changing... http://www.srrb.noaa.gov/highlights/sunrise/calcdetails.html Whilst this may make it more difficult to reconcile 'absolute' timings, perhaps the overall approach could point out any discrepancies in the claimed positions of cameras...such as Altgens for example... Link to comment Share on other sites More sharing options...
John Dolva Posted February 7, 2009 Author Share Posted February 7, 2009 [quote Russ I agree that sometimes things are more simple than they seem and would endorse the view that potential problems should be tackled and explored rather than ignored. As you say, once verified, such data would be very precise and universally applicable. But to point out one example, in terms of solar calculations, the NOAA website states that its solar calculator is based on the algorithms of Jean Meeus which are accurate to within 1 minute for locations +/- 72 degrees latitude and within 10 minutes outside of these latitudes - these error margins being due to atmospheric conditions which are local and constantly changing... http://www.srrb.noaa.gov/highlights/sunrise/calcdetails.html Whilst this may make it more difficult to reconcile 'absolute' timings, perhaps the overall approach could point out any discrepancies in the claimed positions of cameras...such as Altgens for example... jd Russ, interesting, could it be logarithmic? attachment (sorry, mouse skills need work, but still?) ______________________ The formula for locating a photographer and and in turn distance from photgrapher to an object can be widely useful. Link to comment Share on other sites More sharing options...
Frank Agbat Posted February 8, 2009 Share Posted February 8, 2009 John, What am I looking at in your graph? Link to comment Share on other sites More sharing options...
John Dolva Posted February 8, 2009 Author Share Posted February 8, 2009 (edited) (Frank, *(refraction, refractive index of increasing density of atmosphere, incidence angle, declination issues) perhaps a correlaton between latitude and distance light travels through the atmosphere + density and timing error margins) What I'm getting at here (re Atmospheric (perhaps a subset of Astronomic considerations, or a separate major issue, I'd tend to add it to the list as a separate major issue) is that the atmospheric effects could be related to the incidence angle as the sunrays enter the atmosphere, which is denser closer to the earth and denser at the poles (cold) (10 minute error possibility), and that 72 degrees (1 minute error possibility) indicates the 'major' shift in a (ideal conditions) logaritmic curve that determines time errors. Below this, in Dallas (about 33 degrees) the error margin is approaching the near zero error likely at the equator. IOW, Russ, you may have identified the major error margin. And given the sunny conditions and known latitude, humidity, elevation, et.c. in Dallas 11/22/63, we may be dealing with a determinable sub-minute error margin. ??? . attatchment edit : *add, typos Edited February 8, 2009 by John Dolva Link to comment Share on other sites More sharing options...
Frank Agbat Posted February 8, 2009 Share Posted February 8, 2009 Thank you, John... More to ponder! Link to comment Share on other sites More sharing options...
John Dolva Posted February 9, 2009 Author Share Posted February 9, 2009 (edited) Thank you, John...More to ponder! Me, whilst a'pondring too... Went and saw a movie last night. (One of a few I walk out on. Early.) (the last was "Bad Lieutenant', H. Keitel, not because it was a 'bad' movie as such, but because I just couldn't stomach it.) On the long way home through the bush on a winding 2 lane softedge road in near full moon I close an eye and cupped the lens of my glasses (light responsive) (btw wearing glasses most of my life (should have started earlier, my parents became suspicious as I kept running into things, trees, branches etc) and doing a lot of different constuction jobs and surveying, I'm constantly aware of the distortions at the periphery and very aware of trusting tools rather than my eyes re distance, plumbs, etc) to prepare that eye for turning the headlghts off. (done this before on the Null Arbor, a huge treeless flat area of Oz to cross going e/w w/e, where the roads are so straight and it's so flat that one can see a car (lights) coming sometimes half an hour or more before it reaches you (at 110k's). At about 4.1 k's the 'phenomenon' occurs where the single looking oncoming light starts to separate into two, so one can then know roughly when to dip the lights to not blind the oncoming. Anyway, the trick to close one eye preparatory to entering a dark place like a cinema for example makes the visual transition from light to dark much easier. > Is there anwyhere, in any context, anything that comes to mind, anyone, a note of anyone cupping, or closing, an eye, which I'dimagine being SOP for any spook, in the assassination lore? As I was enjoying this little experiment, I found that I could drive confidently at abut 50 +/- 5 k's with the headlghts off. But I also realised that I was, preparatory to the 'experiment', loking at the road with one eye only. Even with the hedlights on, pre turning lights off and openng the closed eye, I had to slow down considerably. What I'm gettng at is that a photo is an image created by one lens (or grouping of) and loked at with two eyes. Having to slow down considerably while covering one eye and with he headlighs on made me realise how critical the stereo vision may be to seing things as they are. No idea what this has to do with the price of eggs in China. But, still, there it is. edit : typos Edited February 9, 2009 by John Dolva Link to comment Share on other sites More sharing options...
John Dolva Posted February 11, 2009 Author Share Posted February 11, 2009 (edited) Here is a film of me driving with cruise control on. How fast am I going? http://www.hotlinkfiles.com/files/2276344_pbzxg/MVI_0233.AVI 10meg download Edited February 11, 2009 by John Dolva Link to comment Share on other sites More sharing options...
Antti Hynonen Posted February 11, 2009 Share Posted February 11, 2009 John Dolva Posted Today, 03:52 AM Here is a film of me driving with cruise control on. How fast am I going? http://www.hotlinkfiles.com/files/2276344_pbzxg/MVI_0233.AVI 10meg download Roughly 60-75 mph or 100-120 Kph. Link to comment Share on other sites More sharing options...
Frank Agbat Posted February 12, 2009 Share Posted February 12, 2009 I was going to postulate about 105 Kph, but I didn't use any mathematical methods to arrive at that conclusion. The curve is marked 90 Kph, and I guessed that they would recommend something around 10-15Kph below the posted speed. Link to comment Share on other sites More sharing options...
John Dolva Posted February 12, 2009 Author Share Posted February 12, 2009 (edited) dbl post Edited February 12, 2009 by John Dolva Link to comment Share on other sites More sharing options...
John Dolva Posted February 12, 2009 Author Share Posted February 12, 2009 (edited) I think this will be very instructional on many levels. Thank you Antti. A reasonable guess. As Frank hinted at "I was going to postulate about 105 Kph, but I didn't use any mathematical methods to arrive at that conclusion.". (my italics) This is precicely it. The way I see it, one or two questions need to be made. (what are they) Then the mathematical method will yield a part of the overall formula(e) looked for here in single lens(or lens assembly) single photo in order to percieve (mathematically) a multi dimensional space wherein every object is correctly located in relation to the camera film surface and also the relation between objects within the photo. Then this can be universally applied. Frank, your guesstimate, and the reasoning for it goes down the path that all guesses go > to where they are argued. This, (and the reasoning is sound (though I can think of counter-arguments, you're assuming things, it's not a guessing game.) (I know you know that ) still, I must say that while your guesstimate is surprisingly hot, it does not answer that which I think CAN be answered very accurately. It's the PROCESS of deriving the answer mathematically that will yield far more than the correct speed. What is needed to be known to precicely mathematically derive the speed? ed : ps Antti, perhaps you percieved I drove somewhat rallystyle (of which the finns repeatedly reign supreme), ie ignore the tracks most drivers use and preempt and follow that which will be the shorter distance thus perhaps giving a 'sense' of speed? Edited February 12, 2009 by John Dolva Link to comment Share on other sites More sharing options...
Frank Agbat Posted February 12, 2009 Share Posted February 12, 2009 John, There are several tools that come to mind that could help with the math side of things. Here are a few things that come to mind that I would ask about: What type of vehicle were you driving? What brand/model of headlights are fitted in the vehicle, and what is their age? What type of camera was used to film the drive? Were any frame rate, aspect-ratio, or other format conversions involved? How and where was the camera attached to the car? It would be informative to know: Where you were driving (precisely). Here is where I'm going with these questions: One method to ascertain distance vs. time, which should reveal speed, would be to research the headlights, their throw, and try to derive the relative distance that an object is initially illuminated before it passes out of the field of view of the camera. This could then be timed and a speed computed. Second thought would be to go back to the location of the drive, and measure the distance between various roadsigns, guideposts, etc. The information on the camera is needed in all cases to (hopefully) understand the optical behavior of the lens. Link to comment Share on other sites More sharing options...
John Dolva Posted February 12, 2009 Author Share Posted February 12, 2009 John,There are several tools that come to mind that could help with the math side of things. Here are a few things that come to mind that I would ask about: What type of vehicle were you driving? What brand/model of headlights are fitted in the vehicle, and what is their age? What type of camera was used to film the drive? Were any frame rate, aspect-ratio, or other format conversions involved? How and where was the camera attached to the car? It would be informative to know: Where you were driving (precisely). Here is where I'm going with these questions: One method to ascertain distance vs. time, which should reveal speed, would be to research the headlights, their throw, and try to derive the relative distance that an object is initially illuminated before it passes out of the field of view of the camera. This could then be timed and a speed computed. Second thought would be to go back to the location of the drive, and measure the distance between various roadsigns, guideposts, etc. The information on the camera is needed in all cases to (hopefully) understand the optical behavior of the lens. Frank, I think we're getting somewhere. Some q's I'll have to think about answering, like where I am or anything related to that. (However I don't hink it is critical). If you can let me know why, it would help. I can say now I held the camera outside the window, though that's prob not much help. There is no deliberate conversion, which is why I dumped the 10 meg in toto as is from the memory stick. PERSPECTIVE obeys certain laws. (rip one frame and check it out?) IMO the following are important variables to quote (slightly out of context perhaps) "measure the ( ed: >A< distance, which distance?) distance". A known distance on a plane paralell to the camera lens(?), preferably, but not neccessarily, at the centre to avoid distortions, (however, knowing lens and 'the formula' or part thereof, one should be able to deduce parspectives, obliqueness, and hence 'the matrix' that forms unit nodes (in space and time (..."ascertain distance vs. time"...) in the area filmed and therefore answer many of the questions.) (Some will be answered in surprising ways, I think.) "The information on the camera is needed in all cases to (hopefully) understand the optical behavior of the lens." yes. ___________________ So what would a formula (or flow chart) roughly look like, using proper variables and unknowns that need to be found out??? I'm hoping the >frame rate< won't be necessary! (though it is a stock standard default settings Canon powershot A70), which is too easy. (remember, there is a hope 'it' can be used in single photo's too). x = ( ? ) Link to comment Share on other sites More sharing options...
Frank Agbat Posted February 12, 2009 Share Posted February 12, 2009 The "where" question would be only to determine the tilt and inclination of the road, and the spacing between road markers, etc. That is really all that is needed. Frame rate is required and critical, because the time variable would be derived from it. Basically, we have to compute s = d/t where s is speed, d is distance, and t is time (assuming for a moment that no acceleration is involved.) The computation of time is derived from the frame rate of the video (how many frames were shot, etc, etc.) That way, we can allow for different frame rate cameras, etc, etc. The computation for distance is where things get quite tricky... Link to comment Share on other sites More sharing options...
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