Motion Z-312 to Z-313:Head or camera?

[David Wimp]

Forward motion of JFK's head between Z-frames 312 and 313 has been
widely accepted. Though frame 312 if very clear, 313 is quite blurred.
I believe that there is very little, if any, actual head motion and that
perceived motion is actually the result of a failure to account for the
effects of the blurring in 313.
Motion blurring is produced by a combination of camera movement and
movement of the objects being photographed. I think it is easier to
follow what is happening in blurs if the camera is assumed to be still
and the image is thought to move across the film. All stationary
objects move at the same rate across the film while moving objects move
on the film at different rates. All the objects being measure here are
in the car, which is moving at a constant rate. The motions of the car
and camera combine to produce an apparent movement of the car across the
film and only this apparent motion need be considered. The value at a
particular spot on the film is actually a combination of all parts of
the image that move across it during the exposure.
A few months ago, I posted a model to explain some of the strange
things observed in frames 402-418. The lamppost is partly invisible
though it has sharp boundaries, a man seems to disappear behind an
invisible post, and a strange green triangle of grass extends into the
street in frame 405. The model assumes that when a bright area is
blurred across a dimmer one (or vice-versa, it really doesn't matter
which comes first), very little gradient is produced at the boundary.
Instead, the bright area obliterates (I used the term dominates in the
original post) the dimmer one and a sharp boundary is produced. What
seems to happen is that a spot on the film which is exposed partly to
the bright region and partly to the dimmer one comes out looking like
the bright region even if the fraction of exposure to the bright region
is very small. I propose no underlying basis for this phenomenon but it
does seem to fit the observations very well. This same phenomenon
occurs in 313. By comparing the widths of the buttons, or lights (or
whatever they are) on the roll bar in 313 to 312, one can see that they
are much wider in 313 due to motion blurring. However, the boundary
between the back of JFK's head and the top of the curb is quite sharp in
313. Likewise, the edge at the top of the back seat is fairly sharp.
How does one account for sharp edges in such a blurred frame? In the
case of the head against the curb, I would explain it this way. The
curb is very bright compared to the head, so all parts of the film hit
by both the curb and the head come out as curb. Similarly, the seat
back is more directly illuminated and thus brighter than the seat top,
so when back is blurred across top, the entire blur appears as top.
The blurring in 313 appears to be nearly horizontal, but which way
is it blurred, right to left or left to right? Since the car is farther
to the left in 313 than 312, I conclude that the blurring is right to
left, i.e., the image of the car is moving to the left across the film.
This means that, if an object producing a blur is brighter than the
background, the right edge of a blur is where the image was when the
shutter opened and the left edge of the blur is where the left edge was
when the shutter closed. Consider the lights on the roll bar. They are
brighter than the grass behind them, so they obliterate the grass when
they are blurred across it. This means that the entire blur comes out
as roll bar light. So the right edge of the blur is where the right
side of the light was when the shutter opened and the left edge of the
blur is where the left side of the light was when the shutter closed.
Now consider the head against the curb. Unlike the lights, the head
could be moving relative to the car. If the head moves to the right
(forward) faster than the car is moving to the left, then the image of
the head would be moving to the right across the film. Otherwise, it is
moving to the left. This means there are two possible interpretations.
If the head is moving left to right on the film, then the boundary
between curb and head represents its position when the shutter closed.
Otherwise, it represents its position when the shutter opened.
Now to actually measure head movement. The key is to measure the
head against a reference point on the car such that both measurements
either represent positions when the shutter opened or when it closed.
Otherwise, the measurement will include camera motion during the
exposure interval as well as head movement! The problem is, we don't
know which end of the exposure interval the position of the head
represents. So we must try it both ways and see if one makes more sense
than the other. I believe that the results obtained from assuming the
head represents a "shutter open" position makes more sense.
In the following table, all results are in a coordinate system in
which the frames are 6 units horizontal and 4 units vertical. The
values represent the differences in lengths between 312 and 313. All
values represent movement to the right.

Seat to JFKhead 0.11 Seat - boundary
of top edge of back seat and curb

RBR to JFKhead 0.02 JFKhead - boundary of
back of JFK's head and curb

RBL to JFKhead 0.11 RBR - right edge
of farthest roll bar light

JBChead 0.10 RBL - left
edge of farthest roll bar light

RBR to seat 0.11 JChead - width of
bright part of Connally's forehead at hairline

RBL to seat 0.00

First, note the measurements between the roll bars light and the seat.
The boundary between the back and top of the seat is moving left across
the top so the bright back should obliterate the top and the resulting
edge represents a shutter close position. The distance to the left edge
of the light , another shutter close position, remains constant. The
"movement" between the right edge of the light and the seat is actually
the camera movement during the exposure interval. Note also that this
is almost the same distance that Connally's forehead expands, which
should be another measure of camera movement. Now observe that
measuring the head against the right edge of the roll bar light, which
is a shutter open position, shows very little movement. Measuring
against the left edge of the light, a shutter close position, shows much
more and that the distance corresponds exactly to the camera motion
measured above. Converting these values to actual distances requires
the field of view of the frames and the distance to the car. If the
distance is assumed to be 60 ft. (a guess) and the FOV is taken to be 10
degrees (I have measured this but not terribly well. I do think it is
ballpark) then 0.11 represents a movement of about 2.3 inches. Not
quite the 3.8 inches that has been claimed, but in the neighborhood.
0.02 represents about 0.4 inches. The FOV and distance together produce
a linear scale factor. If the values are scaled so that the larger one
is 3.8, then the smaller one would be 0.7 inches.
The bottom line is that these measurements are consistent with two
different scenarios. If the head position is taken to be a shutter open
position, then the head moved forward about 0.4 (or 0.7) inches, hardly
a significant amount. In this case, the right light edge to head
difference is just the camera motion and is consistent with the other
measures of camera motion. If head position is taken to be a shutter
close position, the head suddenly moves forward about 2.5 (or 3.8)
inches. In this case, the right light edge to head difference is
actually the head motion and coincidentally is exactly the same as the
camera motion. (This would mean that the forward head motion exactly
matches the movement of the camera so that the head remains on the same
spot on the film. I think the first scenario, being simpler and
requiring no coincidence is the more reasonable assumption unless there
is other evidence to support a forward head motion.

[miker...@gmail.com]

I am bumping this very old post with the hopes of finding David Wimp.

I would like to ask David several questions regarding his theory and hopefully start a discussion on it.

I know that Josiah Thompson believes it to be true and I think that he might even re-write his book "Six Seconds In Dallas" because of it.

I hope to have a thorough discussion about it.

I do not know if it is correct or not, but I suspect it is not based on other data. That is why I would like to talk with David.

If anyone knows David can you please ask him if he is willing to discuss this?

Thanks

[miker...@gmail.com]

On Tuesday, July 2, 2013 4:41:22 PM UTC-5, miker...@gmail.com wrote:
>
>
>
> I am bumping this very old post with the hopes of finding David Wimp.
>
>
>
> I would like to ask David several questions regarding his theory and hopefully start a discussion on it.
>
>
>
> I know that Josiah Thompson believes it to be true and I think that he might even re-write his book "Six Seconds In Dallas" because of it.
>
>
>
> I hope to have a thorough discussion about it.
>
>
>
> I do not know if it is correct or not, but I suspect it is not based on other data. That is why I would like to talk with David.
>
>
>
> If anyone knows David can you please ask him if he is willing to discuss this?
>
>
>
> Thanks

Let me start this off with an animated gif of frames 312 and 313.

For this animation I aligned the two frames to the sprocket holes so the animation shows the movement of the limo relative to the camera's point of view.

It can be seen that the relative movement of the limo (and everyone in the limo) is to the left. I think this indicates that Zapruder moved his camera to the right abruptly causing the image to shift to the left abruptly.

Anyway, I want you to do the following.

When frame 312 is showing place your mouse cursor on a point in an object in the limo. For instance the roll bar. Dont move your cursor and let the animation run. You will observe the point has shifted to the left in frame 313. Now repeat this experiment for many points on objects in the limo. You will observe the same thing, the points shifts to the left in frame 313.

After you have convinced yourself of this leftward movement of all points , place your cursor on the cowlick area of the presidents head. That point does not move leftward. The entire top of the presidents head does not move to the left as every other point does.

That is the anomaly. It is the only area in the entire frame where this occurs. (except for ghost images of policeman)

I would like to get Davids opinion on this.

https://lh5.googleusercontent.com/-XtP5fqKbC_Q/Ubd1mE5tuGI/AAAAAAAABbY/wrOc4EKQ3lQ/w830-h820-no/poiblackwhite.gif

[miker...@gmail.com]

On Tuesday, July 2, 2013 6:01:42 PM UTC-5, miker...@gmail.com wrote:

>
> Let me start this off with an animated gif of frames 312 and 313.
>
>
>
> For this animation I aligned the two frames to the sprocket holes so the animation shows the movement of the limo relative to the camera's point of view.
>
>
>
> It can be seen that the relative movement of the limo (and everyone in the limo) is to the left. I think this indicates that Zapruder moved his camera to the right abruptly causing the image to shift to the left abruptly.
>
>
>
> Anyway, I want you to do the following.
>
>
>
> When frame 312 is showing place your mouse cursor on a point in an object in the limo. For instance the roll bar. Dont move your cursor and let the animation run. You will observe the point has shifted to the left in frame 313. Now repeat this experiment for many points on objects in the limo. You will observe the same thing, the points shifts to the left in frame 313.
>
>
>
> After you have convinced yourself of this leftward movement of all points , place your cursor on the cowlick area of the presidents head. That point does not move leftward. The entire top of the presidents head does not move to the left as every other point does.
>
>
>
> That is the anomaly. It is the only area in the entire frame where this occurs. (except for ghost images of policeman)
>
>
>
> I would like to get Davids opinion on this.
>
>
>
> https://lh5.googleusercontent.com/-XtP5fqKbC_Q/Ubd1mE5tuGI/AAAAAAAABbY/wrOc4EKQ3lQ/w830-h820-no/poiblackwhite.gif

I am going to try to explain, slowly, what I think David Gimp is saying.

It is not going to be easy because I only have bits and pieces of his presentation from years ago. It is titled "A Motion Blur Analysis of the Zapruder Film". It is no longer available on the Internet. If anyone has a copy of it can you please tell where to download it?

Anyway, David is talking about "contrast boundaries". Those are the perceived boundaries in an image between light and dark. David is saying that when an image is blurred the contrast boundaries are altered and the dimensions of the object are no longer valid.

In particular he is saying that he has observed that contrast boundaries are dependent upon the background lighting of the object that is blurred.

If a foreground object is blocking out background light of two different intensities, when that foreground object is blurred it will exhibit two different "contrast boundaries" depending on the light intensity of the background.

His example is the lightpost in frames 413,414 and 415.

When there is no blur, as in frame 413, we see good contrast boundaries for the full length of the light post, even where it crosses the well lighted road.

In frames 414 and 414 the camera blur is increasing. The "contrast boundary" of the light post is changing. It is actually narrower for the part of the light post that is filtering the light from the road than it is for the part of the light post that is filtering the light from the grass.

Here is a link to a gif to show this effect
https://lh5.googleusercontent.com/-gKSjRH2N2ZM/UdRG7CpA5NI/AAAAAAAABv0/AqAoOiYD2nk/w817-h807-no/z412_align413_noblurgimp3.gif


The foreground object is acting like a filter. It is blocking the light which is coming from behind it. When the camera moves light from behind the narrow light post is reaching the camera.

The lightpost is acting like a narrow slit but in reverse. There is a relationship between the width of the blur and the width of the object which will tell us how much we will see behind the object when the camera moves. Since the lightpost is stationary only the moving camera can create motion blur. If the camera moves fast and far enough and the lightpost is thin enough the light post will actually disappear in the image!

There is much more on this and I am sure I do not have everything correct yet.

As I said, I am going to go slow.

The reason this becomes important is because when you are measuring distances between two points on a blurred frame you have to be aware of the change in the apparent dimensions of the object. The apparent dimensions are given by the "contrast boundary".

More on this later.

[miker...@gmail.com]

On Wednesday, March 11, 1998 3:00:00 AM UTC-5, David Wimp wrote:

> Now to actually measure head movement. The key is to measure the
> head against a reference point on the car such that both measurements
> either represent positions when the shutter opened or when it closed.
> Otherwise, the measurement will include camera motion during the
> exposure interval as well as head movement!

To measure a distance between two points in blurred frame you have to pick two points that represent the same moment in time. Both points have to represent the shutter open event or both points have to represent the shutter close event. If you measure the point at the shutter open event on one object against a point at the shutter close event on the other object you will not get a valid measurement. Such a measurement will be either too long or too short by the amount of blur.

Since I know that the distance between any two points on the limo should not change between frames 312 and 313 even though 313 is blurred I am going to first find two such points and show that indeed, the distance between them is the same on frame 312 and frame 313.

I have chosen as my two points the lights on the roll bar and the armrest in the limo behind Jackie.

I have drawn two red vertical lines on frame 312 which shows the distance between these two points.

I then display frame 313 against those two red lines I drew on frame 312.

The distance between the two points does not change, as it should.

The distance between the two points does not change, but to see this you have to notice the following...When frame 313 is displaying the two red lines are at the beginning of the blur for each object. Those two points are at the shutter open event for each of the two objects(rollbar lights and armrest). The distance between the shutter open event for those two objects is the same distance that was measured between those two points on , the unblurred, frame 312.

https://lh3.googleusercontent.com/-VwY_dG1bYRQ/UddMi8WtZSI/AAAAAAAABwU/NVz3tURvows/w737-h311-no/z312_rollbar_armrest.gif


This tells me that I know two good reference points on the blurred frame. I know a good point on the armrest or the roll bar lights from which to measure the back of the Presidents head.

In the following animation I have simply added a marker for the back of the Presidents head. I can use that marker to measure the presidents head to either the armrest or the rollbar lights.

It certainly looks like the distance from the back of the Presidents head and the armrest (or the rollbar lights) gets smaller.

https://lh3.googleusercontent.com/-g5RBsMOOlGw/UddMsOq1txI/AAAAAAAABwo/rECRn9gbnBY/w675-h285-no/z312_rollbar_armrest_boh.gif

But I am not done yet there is more to come....

[miker...@gmail.com]

Once again, here is the gif which shows the apparent movement of the Presidents head forward. The distance between the cyan vertical line and either of the red lines shows the distance on frame 312. When the animation cycles to frame 313 the distance from the back of the head to either red line gets noticeably smaller.

https://lh3.googleusercontent.com/-g5RBsMOOlGw/UddMsOq1txI/AAAAAAAABwo/rECRn9gbnBY/w675-h285-no/z312_rollbar_armrest_boh.gif

So why does David Wimp say that the Presidents head does not move between the two frames?

He says that what we are seeing is an optical illusion. He says that even though we cannot see it, if you look closely you will see what he calls "mach banding" which shows that there is a "ramp" from light to dark at the back of the head and the real boundary of the presidents head, implied by this "mach banding" is at the location of the cyan vertical line.

I am pretty sure that David Wimp is wrong about this and I will explain that in future posts.


Here is a blurb on "mach banding".
http://www.yorku.ca/eye/machband.htm

Here is a link to a web page where he shows his analysis of the presence of "mach banding"
http://joliraja.com/HeadCurbBoundary/Curb-head-intersection.html

[miker...@gmail.com]

David Wimp proposed a model to explain the blur he observed in the Zapruder film, in particular the blur he observed in the light post in frames 400+.

In his model, the light on dark boundaries in the direction of the blur move by the amount of the blur and the dark on light boundaries in the direction of blur do not move.

It is important to remember that blur is the relative motion of objects in the scene and the camera WHILE THE SHUTTER IS OPEN.

Here is an image which illustrates this. In this example the the motion while the shutter is open is from left to right. The light on dark boundary moves from left to right by the amount of the motion. The dark on light boundary does not move.

https://lh4.googleusercontent.com/-qd3D5QuJ0nQ/UdoT4TUCEVI/AAAAAAAABzY/PcHMGxgAEQs/w713-h190-no/BlurMove.jpg

[curtj...@hotmail.com]

Or neither. What if the film was altered? Wouldn't it make it another option instead of assuming it was one of these two theories? It then, could have been a from-the-back shot, with only a portion being shown, or simply a part of a braking of the limo. I believe the ones who claimed seeing an early-on original have seen a definite first back head shot, followed by another. Also, what are you going to do with a Dr. Ryan who has stated in a frame that there was no motion in Z-303 and yet it is moving in Z-302. I think it was altered there myself as Jean Hill is not looking at the President, and Moorman is fixated with her camera straight ahead, and the head shot via her Polaroid would have taken some magic to pan and take that shot.

http://www.mtgriffith.com/web_documents/zfilmaltered.htm

CJ

[Sam McClung]

mebbe kellerman hit the brake a little, causing jfk to lurch forward a
bit...

or mebbe jackie somehow caused jfk to move forward...

seems if the forward movement wasn't caused by z-film alteration, one might
wonder how roscoe white was able to compensate for that movement and hit jfk
right in the right temple...jfk certainly didn't lean forward into the
shot...

alteration could give the appearance of the head moving forward, so that
news persons could proclaim the head moved violently forward...(more likely)

alteration could account for timing problems with the acoustic tests done to
date vs. the z-film, not that the acoustic tests are mainly a farce due to
no testing using suppressed gunfire...

but everyone (almost) gets paid, stone still gets royalties off jfk? the
(skull & bones kkkontrolled) book publishers still make money by not
allowing the entire story to be mainstream? relegated to trolled internet
discussion gruppes and youtube videos kkkontrolled buy the see eye a?

[miker...@gmail.com]

On Sunday, July 7, 2013 8:34:20 PM UTC-5, miker...@gmail.com wrote:
> On Sunday, July 7, 2013 9:54:48 AM UTC-5, miker...@gmail.com wrote:
>

> https://lh4.googleusercontent.com/-qd3D5QuJ0nQ/UdoT4TUCEVI/AAAAAAAABzY/PcHMGxgAEQs/w713-h190-no/BlurMove.jpg

Blur is the motion of an object WHILE THE SHUTTER ON THE CAMERA IS OPEN. The motion may be the result of actual movement of the object or it may be the result of the movement of the camera.

I am going to illustrate the David Wimp model for two cases.

In both cases the background object is the light source and the foreground object blocks the light from the background.

I have labeled the bacground as the "curb" and the foreground as "boh" (for back of head.

The Presidents head as it moves blocks the bright light from the curb.

According to David Wimps model when you have a foreground object blocking the light from a bright background the boundary between light and dark is not always easily visible and a ramp or machbands are formed. The perceived boundary may or may not be the actual boundary.

In the first case the back of the Presidents head moves right to left while the shutter on the camera is open. The boundary between the curb and boh is denoted by red vertical lines. In this scenario the perceived boundary between the curb and boh does not change. Machbands(a ramp) is formed but would be hard to see because of the contrast between the white background and black foreground.

https://lh3.googleusercontent.com/-4UcA_TVBjjc/Udwnoq1N3PI/AAAAAAAAB0Q/teNhPTkdiW4/w676-h180-no/BlurMoveRtoL.gif


In the second case the back of the Presidents head moves from left to right while the shutter on the camera is open. The boundary between the curb and boh is denoted by red vertical lines. In this instance the boundary between the curb and the boh moves to the right. The amount of the move is equal to the amount of the blur.

https://lh3.googleusercontent.com/-sjprCRykLSk/UdwnbMuLYdI/AAAAAAAABz4/tg8GCY64xGA/w676-h180-no/BlurMoveLtoR.gif

[miker...@gmail.com]

On Tuesday, July 9, 2013 10:34:20 AM UTC-5, miker...@gmail.com wrote:

The forward head movement observed between frames 312 and 313 is real. It is not blur. It is real forward head movement.

How do I know it is real?

The bullet struck the President on Frame 312, not frame 313. Specifically, the bullet struck the President during the shutter closed period of frame 312.

The period between frames was 54 milliseconds. The shutter is open for 27 milliseconds and closed for 27 milliseconds.

The shot struck the President some time during the 27 milliseconds that the shutter was closed on frame 312.

The head moved forward during the shutter closed period for frame 312. The forward movement that is seen from 312 to 313 occurred during the interval the shutter was closed.

Here is a schematic
https://lh6.googleusercontent.com/-sLN6qGhG6ts/Ud15ptCVQjI/AAAAAAAAB1I/9Ix8Ii9523o/w958-h422-no/bullet_strikes_head.PNG

Recall, that blur is the result of movement of an object while the shutter is open. The forward movement between 312 and 313 occurred when the shutter was closed,not open. That movement is not blur.

This implies that the position of the head in frame 313 corresponds to the shutter open event for frame 313. The head had already moved in reaction to an impulse on frame 312 and we are getting the first glimpse of it on frame 313.

The movement between the two vertical cyan lines in the following animation is real movement of the head that occurred during the shutter close period of frame 312.

https://lh5.googleusercontent.com/-qrsMOeH_K58/Ud132LuQZeI/AAAAAAAAB0s/ABWlhwtmfN4/w737-h311-no/z313_rollbar_armrest_boh.gif

The blur induced during the shutter open period for frame 313 was in the opposite direction to the forward movement caused by the impulse.

I will discuss that in the next post.

[miker...@gmail.com]

If, as David Wimp and myself agree, the rear boundary for the location of the Presidents head we see in frame 313 is a shutter open event then why is the blur that is seen on the subsequent part of frame 313 relevant?

If the location corresponds to the shutter open event for frame 313 then the head existed in that location immediately prior to the opening of the shutter. The magnitude of the movement is determined completely by the last visible location of the boundary for the head on frame 312 and the initial boundary on frame 313.

[miker...@gmail.com]

Just adding a small correction to previous post...

If the location corresponds to the shutter open event for frame 313 then the head existed in that location immediately prior to the opening of the shutter. The magnitude of the movement is determined completely by the last visible location of the boundary for the head on frame 312 and the initial boundary on frame 313.

Actually, the movement is not completely determined. The forward head movement prior to the opening of the shutter on frame 313 could have been greater than what we see on film.

[miker...@gmail.com]

On Friday, July 12, 2013 10:47:43 AM UTC-5, miker...@gmail.com wrote:

This animated gif measures the forward movement of the head between frames 312 and frame 313. It measures from the roll bar light right position in the limo (red vertical line) to the BOH(cyan line). The distance between the two cyan lines is the measured forward movement. David Wimp estimates this distance as 7 tenths of an inch. I think it is much greater than that.

https://lh4.googleusercontent.com/-fJqRrm-UXNg/UeYbRk_4oaI/AAAAAAAAB4I/yufN-KuLevs/w737-h311-no/312RBR_BOH.gif

[miker...@gmail.com]

In the following animation the distance between the two vertical cyan lines is the amount of forward movement of the head meastured from the right side of the roll bar light.

I have translated the two cyan lines to the roll bar in order to measure the distance relative to the width of the roll bar. The roll bar is known to be 5 inches wide.


https://lh3.googleusercontent.com/-MNIH44GZTDg/UeaF64viA3I/AAAAAAAAB4k/0sINLBfKqsQ/w737-h311-no/boh_on_rollbar.gif


Here is the measurement on the width of the roll bar.

https://lh4.googleusercontent.com/-ZFNzZrlGDj8/Ud7qXaDxqaI/AAAAAAAAB18/vfEAuETts00/w900-h654-no/crossbar-200.jpg

[miker...@gmail.com]

Here is another animation. This one shows the forward movement of the back of the head relative to the length of the blur. They are not the same length. The blur len is larger than the movement of the back of the head.

The blur line is known to be about 3.8 inches long.
https://lh3.googleusercontent.com/-9fvLIcuh_Ro/UebE34Sq2WI/AAAAAAAAB5g/vcyaw4G75Hs/w737-h311-no/boh_blurline.gif

[miker...@gmail.com]

On Wednesday, July 17, 2013 11:25:33 AM UTC-5, miker...@gmail.com wrote:

Here is an example which will give to large a measurement of the Presidents head.

It uses the shutter closed position of the roll bar and the shutter open position of the back of the head. The distance calculated will be to small by the amount of the blur. If you use this measurement you would calculate that the President's head moved too far forward.

https://lh6.googleusercontent.com/-dvLUepvI02E/UefuQLBrlKI/AAAAAAAAB58/P6BDL3PsoVA/w737-h311-no/mistake.png

[miker...@gmail.com]

On Thursday, July 18, 2013 8:35:26 AM UTC-5, miker...@gmail.com wrote:
> On Wednesday, July 17, 2013 11:25:33 AM UTC-5, miker...@gmail.com wrote:
>
>
>
> Here is an example which will give to large a measurement of the Presidents head.
>
>
>
> It uses the shutter closed position of the roll bar and the shutter open position of the back of the head. The distance calculated will be to small by the amount of the blur. If you use this measurement you would calculate that the President's head moved too far forward.
>
>
>

Here is the mistake again.

https://lh6.googleusercontent.com/-dvLUepvI02E/UefuQLBrlKI/AAAAAAAAB58/P6BDL3PsoVA/w737-h311-no/mistake.png

Itek did an analysis of the amount of forward movement of the Presidents head and determined that the Presidents head moved forward about 2.3 inches.

Itek measured the movement of the Presidents head against 20 fixed locations inside the limo. They used 3 different methods to make this calculation.

Here is a link to their analysis
http://www.maryferrell.org/mffweb/archive/viewer/showDoc.do?docId=60448&relPageId=3

David Wimp believes that Itek's results are incorrect and I think he believes they are incorrect because Itek made the mistake illustrated in the above animation.

In other words, I think David Wimp is saying that Itek made measurements of the Presidents head as if the head was in the shutter closed location which would mean that Itek measured the back of the Presidents head against shutter closed positions of all the fixed points in the limo. (There is no mention in the Itek report regarding what shutter position they thought the Presidents head was in)

If Itek made that mistake the resulting head movement would equal to the length of the blur (if the Presidents head did not move at all).

Since Itek measured 2.3" of head movement it implies , if they made this mistake, that the blur on the film is 2.3".

However, the length of the blur is clearly larger than 2.3 inches as one can see by comparing the blur line to the width of the cross bar. The cross bar is known to be 5" wide.

https://lh3.googleusercontent.com/-0BQYeB_gsB0/UegG-ElX_XI/AAAAAAAAB6Y/MJaHie2DOLA/w737-h311-no/crossbar_with_blurline.png

If Itek made the mistake they should have measured a much larger forward movement of the Presidents head.