A correct attribution for the "Flash Effect" photo?

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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Fri Jan 24, 2020 8:27 am

Hello,

to Mr. Wadinga who said: "Hans, could you explain why you say : 2.No, or just only very roughly. Since drawing a perspective line through the centre of the ellipses you have used would surely intersect Bismarck amidships ": we can calculate with trigonometrie the angle from the muzzle end plans to photographer (only incertitude is the exact initial measures, due to image quality limitation) by estimating the size of the minor and major axis of the apparent ellipses.
I have not found any way to calculate where this plan goes to the horizon. It can end behind or ahead the Bismarck and not in line. Optical effect is that it aligns very roughly to Bismarck but it is not enough.
I am unable to calculate exactly. Can you or anyone else ?
I agree the photographer is at 2-5 meters from gun muzzles, but we can not say if at the railing or more to centerline. It depends from guns orientation and courses.

to Mr.Jurens who wrote "The chances of having a photographer wandering about the weather decks and basically just getting in the way in a combat situation are pretty slim. " : the Prinz Eugen film cameraman was on the weather deck close to railings during the battle (no superstructure, no deck in the camera field at any time, also when ship is rolling or shaking, only railings. The film camera was outside when on the engaged side and Prince Of Wales was firing too).
Lagemann and other authorised photographers were likely outside too. I do not see any reason why this excellent photo (high quality) should have been taken from enclosed position when the photographer was on disengaged side, far from main guns in action.
Has anybody any information suggesting that this cameraman was sheltering ?
In all proposed drawings the photographer is very close to railings (logically, when Bismarck was almost passing behind the Prinz Eugen).

Due to small angle from gun muzzle ends and Prinz Eugen course, the most probable situation is Mr. Bonomi (posted by Mr. Virtuani at page 12) drawing, with gun trained c 30 - 40 degrees to starboard (further calculation is needed), from very close to railings.
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viewtopic.php?f=1&t=8756&start=165#p85382

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Re: A correct attribution for the "Flash Effect" photo?

Post by wadinga » Fri Jan 24, 2020 12:42 pm

Fellow Contributors,

Thanks are due to Herr Nilsson who has provided a photograph showing the midships starboard 105mm mounting rotated to a "lookout" position, thus providing important evidence that unengaged mounts might be in such an orientation during DM. It very closely resembles the situation in the drawing he posted on 13th January. Later he added Bismarck to the drawing but positioned at the end of an alignment from the photographer POV through the muzzles which is incorrect compared with the photo (through shortage of time). We are all in debt to his making his drawing skills available here to help work through this analysis.

Later on 17th Jan he reposted a new version with the explanation
I don't understand your problem, it's still just a projection of the plane. However...
and the caveat
Caution: This picture isn't accurate! It's just for illustration purposes!
Hans also has responded with:
I have not found any way to calculate where this plan goes to the horizon.
by which I am confused. Maybe I don't understand the laws of perspective, in which case remedy my ignorance, but to me simply drawing a line through the end of the gun muzzles intersects Bismarck amidships. This is essentially a flat 2D world, since the POV, the gun muzzles and the Bismarck (and the horizon) are all at the same height for all intents and purposes. We are not looking down (or up) from a large vertical displacement creating artificial alignments, so what we see is straightforward. Apparent alignments are real alignments. Since the plane of the end of the gun muzzles is at right angles to the orientation of the gun barrels it follows the barrels are at 90 degrees to the bearing of Bismarck. The alignment of the barrels is the alignment of the mount.

It would be valuable to have the 17th Jan drawing, but with Bismarck correctly positioned on the extension of the alignment of the gun muzzles, and rotated to the correct angle on the bow. As Herr Nilsson has observed there is little or no evidence whether the mount is fully forward or rotated to his suggested position, as shown in the photo. I would submit that this represents about the absolute limit of possible clockwise rotation before the photographer "leaves" the deck.

All the best

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Re: A correct attribution for the "Flash Effect" photo?

Post by Herr Nilsson » Fri Jan 24, 2020 1:48 pm

Sean,

my drawing from 17th has no information in vertical direction.

Maybe I'm wrong, but in my opinion the upper and lower edges of the muzzles create a triangle and one edge of the triangle is far outside of the picture (trapezoid)(blue). Looking from above the whole plane of the triangle is in front of Bismarck.

If Bismarck would be intersected whilst looking from above, the missing edge of the triangle would be in front of Bismarck (red).
Perspective (2).jpg
Perspective (2).jpg (35.27 KiB) Viewed 431 times
Regards

Marc

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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Fri Jan 24, 2020 1:51 pm

Hello,
to Mr. Wadinga who wrote: "to me simply drawing a line through the end of the gun muzzles intersects Bismarck amidships. This is essentially a flat 2D world": the optical effect may be this, but there is no way to calculate where this line ends, it depends from Bismarck distance.
Simply drawing a line on a 2D image to simulate a 3D environment is fundamentally incorrect: even doing so (hope my drawing is clear), such line ends c 200 meters behind Bismarck, in her wake, as per Mr.Nilsson Jan 17 drawing, but this is not proving anything.
The guns are (or apprear in the uncroped image) slightly elevated.
Please, could you explain which mathematic method you use to reach your conclusion ?

hans
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Re: A correct attribution for the "Flash Effect" photo?

Post by Bill Jurens » Fri Jan 24, 2020 6:22 pm

Photogrammetrically, all items in a photo tend to recede in a radial pattern away from the exact point at which the camera was pointed, which is -- at least in English terminology -- called the 'principal point'. Very long ago, we used to make maps using a device, appropriately defined as a 'radial line plotter' which took advantage of this phenomenon. The observation that the radial line in this case points somewhat to the left of Bismarck says something to be sure, but it's difficult to say exactly what without access to the full negative, and even then, because we don't actually know the orientation of the muzzles in space, attempting to use their image in an analytical form is, at best, highly problematical. For what it's worth, usually photographers tend to place the subject near the center of the frame, so it would be reasonable to assume as a first 'rough cut' that the principal point probably lies somewhere on the image of Bismarck. Unless it doesn't. The photographer may have been somehow constrained so as to expose the frame with Bismarck not at the center, and somewhat to the right, with the 'extra' material to the left, for whatever reasons, cropped out in printing. We just don't know.

Although some very clever and creative analysis has been submitted so far, the plain fact is that attempting to determine the relative courses and distances from this photo is probably futile. Although we can derive some sort of idea of the target angle of Bismarck from the photo, determining the relative course of the Prinz Eugen solely based upon the shadowy image of two gun muzzles in the corner of an image is highly speculative at best, since we really don't know where the muzzles are -- that is what mount was being photographed -- and we really don't know at all what azimuth and elevation the muzzles were at when the image was exposed.

I just don't think there is really enough information in this image to derive much from it that could be considered as other than very broad speculation. It's sort of an historical Rorscarch test, probably telling more about the interpreter than the subject.

Bill Jurens.

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Re: A correct attribution for the "Flash Effect" photo?

Post by Bill Jurens » Fri Jan 24, 2020 7:06 pm

P.S. I'm certainly glad to see that reasonable commentary and criticism seems to be the new order of the day in our discussions. This has become (again) a pleasant place to visit, and makes the moderator's job much, much, easier.

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Re: A correct attribution for the "Flash Effect" photo?

Post by wadinga » Mon Jan 27, 2020 1:14 pm

Fellow Contributors,

Yes Bill it contrasts markedly with some of what has gone on before and that vast improvement is purely down to the Moderator acting entirely appropriately and with commendable restraint under extreme provocation. It would be even better if we could tempt in more contributors with their observations, now the atmosphere has indeed become more collegiate.

Can I ask a question about:
Photogrammetrically, all items in a photo tend to recede in a radial pattern away from the exact point at which the camera was pointed, which is -- at least in English terminology -- called the 'principal point'.
Presumably this is true for all objects in the field of view, the vast majority of which are randomly positioned, relative to one another, and is an optical effect of the distance between them diminishing as they approach infinity. However these muzzle ends are not randomly positioned relative to one another and they are orthogonal to the axis of the mount. Also Bismarck is not at infinity. Furthermore we agree they are physically very close to the photographer and with a vertical displacement of little more than a metre.

Hans has helpfully drawn two variants and I feel the alignment is more accurately drawn in the first than the later. In the latter the muzzle on the right is not hit in the centre but low down and the small rotation of the line around the close pivot of the muzzle on the left is what moves the intersection astern of Bismarck. A line drawn using the top margins of the muzzles, instead of attempting to identify a centre in the murk, intersects Bismarck neatly on C and D turrets. This surely not an optical effect, but real.
The photographer may have been somehow constrained so as to expose the frame with Bismarck not at the center, and somewhat to the right, with the 'extra' material to the left, for whatever reasons, cropped out in printing. We just don't know.
Given the proportions of the image re say, a 35mm negative is it not reasonable to assume that the "muzzle version" of the image very probably represents the full image, since they contribute little for the average user, disappear in many reproductions and no larger version incorporating more extraneous detail of them has ever appeared?

I can provide no mathematical proof for my "broad speculation" but I consider this analysis worthwhile especially in the context of NH 69729
www.history.navy.mil/our-collections/ph ... 69729.html

not necessarily taken by the same photographer from the same location but showing Bismarck approaching at right angles to a handrail aboard PG. Despite constant attempts to denigrate any conclusion that the ships are proceeding at right angles to one another, my conclusion remains firm. Notably because these are chains displaying catenary and not solid bar handrails. None of the locations I have identified aboard PG where the rails go around obstructions have cjains, only solid rail. I believe chains are only used where the rails are parallel to ship's keel.

All the best

wadinga
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Re: A correct attribution for the "Flash Effect" photo?

Post by Bill Jurens » Tue Jan 28, 2020 5:52 am

Attempts at any sort of photogrammetric analysis of this photography are, at best, extremely "iffy". I visited the Naval Historical Center website and noticed that their digitized images seem to contain what appears to be a slight curl on the right-hand side, which suggests that they were not made on a flat-bed scanner, but simply represent rather offhand photos of prints in the collection. This sort of thing is not to serious when the image is being used just for visual reference, but more-or-less destroys any ability to do photogrammetric measurements, where errors in hundredths of a millimeter can often be significant. Proper photogrammetry is REALLY picky work.

I doubt if there is anything further that can be done without access to the original photography, or at least to something close to that. Ideally, one would have a negative, although even then the quality of the measurements which could be extracted therefrom is problematical as very few lenses, even for high-quality cameras, are of photogrammetric quality. In most cases hand-held cameras are really designed to give one the maximum amount of light-gathering capability, which often comes at the cost of fairly significant geometric distortion, particularly close to the edges of the frame, and particularly when the lens is used nearly 'wide open', which, due to the low film speed available at the time was likely the case in Denmark Strait. Further, most of these lenses were not really well corrected for errors due to variations in subject coloring insofar insofar as almost all photography back then was done in black-and-white. In most cases this represents a good tradeoff because small geometric distortions are rarely noticed or considered important in 'snapshot' photography. There's another problem, too. Most photogrammetric cameras are of fixed focal length and permanently focused at infinity, because most photogrammetric subjects are nearly at infinity anyway. Adjusting the focus away from infinity, which most 'snapshot' photographers would consider essential, causes problems because the projected geometry changes as the lens elements move. Many years ago, I did a variety of tests with various consumer grade cameras to determine if they could be used, in a pinch, to substitute for a photogrammetric camera. OK for approximations, not for anything much better than this. Focal lengths were only approximate, within perhaps 1.5% of the 'published' value, so a nominally 150 mm lens might have an effective focal length of something between 147 and 153 mm. And people kept changing the focus. Photogrammetric cameras have both a published 'nominal' focal length, of (say) 150mm, but their actual focal length, measured carefully in the factory, and chosen to minimize distortions, is always something different, and is stamped on the lens, to a hundreth of a millimeter or better, e.g. 152.56mm

I suspect, but have no way of knowing for sure, that the original negatives -- which were of little use militarily --were retained by the photographer, who probably allowed a limited number of prints to be made in the ship's darkroom to be given out at souvenirs. Other images -- probably better ones -- were likely supplied to various and sundry news bureaus, who would have screened them for publication. So, what we really have are a set of surviving photographic prints, in various sizes and scales, with nothing to track back to the original image. If negatives DO exist, it is quite likely that they are not real negatives at all, but so-called 'copy negatives' made by re-photographing a print. In such cases, little or no effort was usually made to maintain the photogrammetric geometry of the subject. The original negative was likely cropped in printing if nothing else by the negative holder in the enlarger, and -- if copy negatives were made -- may have been cropped again slightly to fill the new negative with the old picture. What's even worse, in many cases old 'analog' negatives have been digitized, which can further degrade the image significantly. Copying a photo NEVER improves the image -- although the copy may look more pleasing to the eye, you can be sure it contains less information than the original did.

It would be useful if someone could visit the German archives to see exactly what, if anything survives. I suspect that at best they have copy negatives. But it would take an archivist, and perhaps a skilled photographer experienced in pre-digital imagery to tell for sure.

Analysis via receding lines converging on the principal point can be confusing, and is largely dependent upon the geometry. Lines are only radial when the subject is vertical and the photographic plane is perpendicular, or nearly so, to the camera's line-of-sight. On conventional aerial photography, one can estimate the position of the principal point by projecting things that are known to be sharp and vertical, e.g. the vertical corners of a building, towards the center. But this really only works when the corners are actually vertical. And it's only an approximation at best. Sometimes pretty good, sometimes pretty bad. And, it only tells you, at best, where the camera was pointed at the time of photography, which is not really enough to go on for further work that is not very highly speculative. Going farther than this, though it might be interesting in an academic sense, would take a great deal more text and explanation, basically moving us into the beginnings of a formal course in photogrammetry.

As I once taught this stuff, I can go on more-or-less forever...

Comments, as always, welcome.

Bill Jurens

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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Tue Jan 28, 2020 8:13 am

Hello,

to Mr.Wadinga writing: 'Hans has helpfully drawn two variants' :
sorry, what you mean for variants, please ? My drawing is trying to position the centres of the muzzles ends but the green lines (axis of ellipse) are not well visible: the right muzzle is seen bigger than the left muzzle, due to distance of cameraman from muzzles. It was first time I posted a drawing and I did have to post it more than once.
Wherever the line ends, it is the methodology that is not correct, because it consider a 2D line drawn from unfocused (muzzle ends) images reliable for a 3D study where Bismarck distance is not exactly known. Mr. Jurens confirmed in his last post saying: "Analysis via receding lines converging on the principal point can be confusing, and is largely dependent upon the geometry."
Mr.Nilsson drawing of a plan is more interesting, but I do not know if it is much more correct.
Connecting the top margins do not change things so much (while method is again not correct to me). I think there is no way to say where the plan intersects Bismarck course.

and writing: "None of the locations I have identified aboard PG where the rails go around obstructions have cjains, only solid rail. I believe chains are only used where the rails are parallel to ship's keel. " :
'Non-solid railings' are present (see PK film and Prinz Eugen photos in Philadelphia) in more than one position on the boat deck and on the weather deck. At least a couple places where they are 'oblique' to the ship keel is visible in a photo from Philadelphia and there are others on both decks.
Here an example: image is very dark but solid railings are visible, 'oblique' chains are not (downloading and enlarging the image).
Eugen Railings.png
Eugen Railings.png (99.32 KiB) Viewed 303 times


to Bill Jurens writing: "Although some very clever and creative analysis has been submitted so far, the plain fact is that attempting to determine the relative courses and distances from this photo is probably futile. "
I agree. About distance, at least it is not a huge one, I say less than 1000 yards. I think your first estimation of c 250 meters is not far from reality.
If a telephoto lens was used, the gun muzzles would never be so much 'focused' from a distance of 2-5 meters.

Also I agree with Mr. Jurens that photos cannot be used to determine exactly courses distances and speeds. Still the PK film and the photos are the only information available to determine Bismarck course (plus the Prince of Wales range estimation plot to some extent and for limited timeperiod). Mr. Bonomi did it in a very good way. Reading back threads on the forum, I am more and more impressed by his knowledge and correct interpretation of images and information.
I feel nobody has yet done anything better than his work: this work is based only on film study and photographs interpretation. If we don't consider images, no battle can be determined.


hans

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Re: A correct attribution for the "Flash Effect" photo?

Post by wadinga » Tue Jan 28, 2020 9:56 am

Fellow Contributors,

Hello Hans thanks for the photo. I believe you are indicating a location for the midships 105mm mount, where a small hinged three sided deck extension is used when the mount is swung outboard. Indeed this has chains but since two sides, forward and middle do not give the required angle and the after one is outboard of the mount under action stations conditions, there is a lot of "if only" required to get the photographer to the right place. Is there a Bu-Ord reference to find the source photo, where it might not be so dark. Can you indicate the other "angled to the stern" locations of chain rather than handrail?

Hello Bill, thanks for your forbearance in explaining these matters to me.

All the best

wadinga
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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Tue Jan 28, 2020 10:18 am

Hello

to Mr. Wadinga:
here a better picture of same mount. Chains and 'solid' railings are clear. They are the forward 105mm mount on upper 'boat' deck. Same for the center 105mm (on weather deck). There are other positions.
PE Railings.png
PE Railings.png (127.71 KiB) Viewed 297 times
The photographer may have been in more than one position (impossible to say where precisely) but chains oriented to Bismarck are present at least on 2 decks from fore to aft of superstructure.
They all match Bismarck on course 220° and Prinz Eugen on course 280°as per drawing posted by Mr. Virtuani (from Mr. Bonomi), same for Mr. Nilsson drawing with Prinz Eugen on 270°.

hans

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Re: A correct attribution for the "Flash Effect" photo?

Post by Bill Jurens » Tue Jan 28, 2020 5:10 pm

Mr. Zurbriggen wrote:

"[the photos] all match Bismarck on course 220° and Prinz Eugen on course 280°as per drawing posted by Mr. Virtuani (from Mr. Bonomi), same for Mr. Nilsson drawing with Prinz Eugen on 270°."

Thanks for your commentary. MIght you describe the detailed methodology whereby compass courses are derived from this particular image? How do we know, for example, that Bismarck was on course 220 degrees when the photo was exposed?

Bill Jurens (just a guy...)

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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Tue Jan 28, 2020 6:16 pm

Hello,
to Mr. Jurens writing: "MIght you describe the detailed methodology whereby compass courses are derived from this particular image? "
I never said that courses can be derived from images. On the contrary, I said courses cannot be derived only from photos (see my 3rd post at page 13). Might you post where I should have said what you write above ? Thanks
I say that the photos match (are compatible with) the drawings proposed by Mr.Virtuani and Mr. Nilsson. They also match Mr. Bonomi battle map.
Hope it clarifies and sorry if I was unclear.

hans

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Re: A correct attribution for the "Flash Effect" photo?

Post by Bill Jurens » Tue Jan 28, 2020 8:53 pm

O.K. Reading the memo again, I can see that I somewhat misunderstood what you were getting at.

That being said, were the proposed tracks themselves not, at least in part, derived from the photos? If so, of course they will match, but only because it's a circular argument. One can't use the tracks to justify the photos and the photos to justify the tracks, as one can arrange these in variety of ways which are internally consistent with one another, but nonetheless result in considerably different reconstructions. Certainly the photograph is compatible with virtually any compass course taken by Bismark, provide we are willing to accept virtually any compass course taken by Prinz Eugen. The photo may, arguably, be capable of representing the relative angle between the courses of Bismarck and Prinz Eugen, but because of the poor quality of the image, even that derivation is -- or would seem to be -- highly disputable.

I suppose we could take one step back and ask exactly how the tracks were derived. So far as I know, there is -- at least for Bismarck -- only one significant source for that, i.e. Prinz Eugen's track chart, which seems to be in and of itself seen to be somewhat less than optimal. The only thing that seems reasonable to derive from the photograph is the rough target angle to Bismarck, and even that has been disputed by various observers.

I'm honestly not trying to be argumentative here; I would just like some help in deriving the logical chain by which the reconstruction regarding the specific courses being mentioned was done. If we had the step-by-step method, then that would allow more people to understand the logical chain, and permit a sequential assessment of the validity of each step in the process.

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Re: A correct attribution for the "Flash Effect" photo?

Post by hans zurbriggen » Tue Jan 28, 2020 9:01 pm

Hello,

to Mr. Jurens writing: "O.K. Reading the memo again, I can see that I somewhat misunderstood what you were getting at.
That being said, were the proposed tracks themselves not, at least in part, derived from the photos? If so, of course they will match, but only because it's a circular argument. One can't use the tracks to justify the photos and the photos to justify the tracks, as one can arrange these in variety of ways which are internally consistent with one another, but nonetheless result in considerably different reconstructions"
Thanks, it's for sure my fault for expressing myself in an unclear way.
Can you show a single different consistent interpretation of the photos and tracks ?
The only consistent one is Mr. Bonomi map with photos and film photograms. No circular argument, only interpreting all images in a consistent way.
He has explained his method in several threads in the past on the forum.
One cannot derive courses and distances from a single photogram. Putting together the whole PK film and the photos however there is only one consistent solution presented up today: the one proposed by Mr. Bonomi, without any polemic intent.

hans

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