Determining Distances from Photographs

Discussions about the history of the ship, technical details, etc.

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Matthias
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Post by Matthias » Sat Feb 04, 2006 1:57 pm

Hello!

Robert, I'm not sure I catched your point, but seem to me that the ship you see in the painting forward to Bismarck's bow is Prinz Eugen.The perspective of the painter was not from the Prinz Eugen bridge, but from an immaginary point behind the two ships, about a quarter from Bismarck's aft bow, starboard side.In effect in this sense the paint is perfectly fitting with Antonio's reconstruction, Bismarck firing to Prince of Wales with the aft turrets and Prinz Eugen still sailing forward her ... :think:

Matthias
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Post by Robert J. Winklareth » Sun Feb 05, 2006 9:00 pm

Hallo Matthias,

You are correct in your comments. Since these were supposed to be combat sketches, I initially jumped to the conclusion that they were made from the perspective of Lt. Schmitz located on the Prinz Eugen. After a more careful analysis, I agree that they do depict the Bismarck at about 0600-0600-1/2 and still some distance astern of the Prinz Eugen.

My comments about the sketches exacerbating the disprepancy between Antonio's diagram and the photographic interpretation are therefore not valid and are withdrawn. That still does not answer the question as to how the Bismarck could be 1340 yards astern of the Prinz Eugen at 0608-1/2 and then be abreast of the cruiser at 0609, just a half minute later.

Thanks for correcting my error and best regards.

Bob

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Schmitz painture

Post by Antonio Bonomi » Mon Feb 06, 2006 12:42 pm

Ciao Bob, Mattthias and all,

I am glad that my post has provided some value add on the determination of the correct Bismarck versus Prinz Eugen relative position and course track during the initial phase of the battle.

As I wrote you the initial photo showing the first salvo is positioning the Bismarck some like 2500 meters ( 2700 yards ) back to Prinz Eugen on her wake.

But than of course Bismarck had 3 possibilities, remain on the Prinz Eugen wake, sail a port course or sail a starboard course still following and catching up on Prinz Eugen.

Here an example of the 3 possibilities Bismarck could have had :

http://hmshood.com/cgi-bin/i/denmarkstr ... ns_map.jpg

I think you will all agree with me now that this historical important painture do confirm that Bismarck was sailing a starboard course while catching up on Prinz Eugen due to her delta speed.

The painture shows Bismarck at the exact moment Hood exploded, so at 06.00 and some seconds.

So now Bob you can look for the Prinz Eugen wake on Bismarck port side clearly painted and judge yourself, making up your own mind about what Ltnt J.C. Schmitz-Westerholt was telling us about that particular historical moment he depicted for the Ober Kommando of the Kriegsmarine.

On my article in fact, on the most recent map version I have published on December 2005, that is exactly what I have showed : a Bismarck course on Prinz Eugen starboard side, just as this painture demonstrate.

Ciao Antonio :D

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Various lenses

Post by phil gollin » Tue Feb 07, 2006 11:32 am

As a complete novice in such things, what effect does different lenses have on the theories mentioned above ?

I.E. do they work with any sort of lens, or only on the one quoted (28mm ????)

Thanks

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Lenses

Post by Antonio Bonomi » Tue Feb 07, 2006 1:57 pm

Ciao Phil and all,

here something for you to learn the concept :

http://www.dpreview.com/learn/?/Glossar ... gth_01.htm

and

http://www.rapitron.it/guidaobE.htm

Those photos were very likely all taken with a 50 mm fixed focal lenght using a Leica or a similar photo camera that was the standard equipment used by PK ( Propaganda Companie ) soldiers ( a kind of war reporters ) that were on board Kriegsmarine ships.

The 50 mm fixed focal lenght do have an angle of 46 degrees.

The first salvo photo ( Nh 69722 ) do demonstrate the utilization of that angle-lens as the fixed structures-plates of Prinz Eugen can be used to verify it.

viewtopic.php?t=273&postdays=0&postorder=asc&start=0


Some thinks that other photos could have been taken with different lenses but that is not my opinion.

So far all the time what I find is that they do evaluated cropped or partially printed photos, as soon as you have the full size photo than you realize all of them were taken with a 50 mm standard lens.

Please do not imagine that 65 years ago they had photo camera were was so easy to change the lenses, not surely like recently standard photo camera were you had fast changes possibilities.

The confirmation of a single camera and maybe even a single film can be found on several photos were Mr. Lagemannwas having difficulties to put the subject on focus before shooting the photo.
The all battle rested for 14 minutes only.

You can try to imagine the photo reporter ( Lagemann ) moving around on Prinz Eugen that was engaged in battle, under 15 inch ( 380 mm ) Hood shells, with flak guys shooting the Sunderland airplane ( and Lagemann often used the flak platforms to shoot photos from ).

He went from one side to the other of the Prinz Eugen few times, and moved from the starboard aft 105 mm flak gun platform to midship and to port side shooting photos.

I do not think that changing his camera lens was his priority and I can hardly see why he needed to change that with a wider angle ( 28 or 35 mm ) as the subjects ( Bismarck or the enemy ships ) were just perfectly taken with a 50 mm lens.
He did not had a zoom ( 80 or 300 mm ), otherwise we were going to have wonderful photos of Hood and Prince of Wales too, while he shooted with the 50 mm lens to them as well.

In particular that day on board Prinz Eugen there were those gentleman from Propaganda Kompanie :

X. Lagemann ( do not know his rank ) that was the official Prinz Eugen photoreporter.

Ltnt ( Reserve ) Julius Ceasar Schmitz_Westerholt ( Kriegsmaler ) so a painter with the duty to make drawings, sketches and paintures of the events at sea.

Kpt Ltnt ( Reserve ) Fritz Otto Busch ( Kriegsmarine Magazine director during War period ).

Plus 2 team's of Propaganda Kompanie with Film Camera ( using a standard for that time 35 mm film ), those made the film sequences we can see on some documentaries.

Bismarck was similarly ( probably even more ) equipped with Propaganda Kompanie guys, but they all die on May 27th, 1941.

When they tryied to have the Arado leaving Bismarck all their material was collected together with the ship war diary ( KTB ), everything lost at sea.

Ciao Antonio :D

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Post by Robert J. Winklareth » Fri Feb 10, 2006 1:13 am

Hi Phil,

You have a very good question, and for a novice, the methodology for determining the distance to another ship by photo analysis can be a bit daunting, especially when dealing with abstract values. Familiarization with a 35mm camera and its various interchangeable lenses would be helpful in your comprehension of the subject, but it is really not all that difficult to understand. Let’s go through the process one step at a time.

As an example, let’s assume that the Bismarck, which was 820 feet long, is lying in the harbor and is perfectly square to your line of sight. If you wanted to take a picture of the Bismarck with a 35mm camera and 50mm focal length lens with an angle of view of 46 degrees, you would have to be a distance of 1170 feet away from the ship to have her entire length fir exactly within the frame of the picture.

If you wanted to take the picture with a 35mm wide-angle lens (angle of view 63 degrees), you would have to get closer to a distance of only 810 feet away from the Bismarck to have her entire length fit exactly within the frame of the film. If you wanted to take the picture with a 90mm telephoto lens (angle of view 26 degrees), you would have to back away to a distance of 2145 feet away from the Bismarck to have her entire length fit exactly within the frame of the film.

The length of the subject filling the entire width of the frame of the film is called the “field of view” of the lens at that range. The focal length and the angle of view of the lens used would determine how far away you have to be to get a specific field of view. With any lens, its focal length and the angle of view remain constant, but the field of view is directly related to the distance that the subject is away from the camera.

Now lets look at an imaginary photograph of the Bismarck in which the entire frame of the film has been enlarged to a 6-inch x 9-inch image on the print. The Bismarck is still perfectly square to the line of sight from the camera, and she measures exactly 4.50 inches across. Since the width of the picture is exactly twice the length of the Bismarck, the field of view at the location of the Bismarck is 1640 feet.

If the Bismarck had not been exactly square to the line of sight, the field of view at the distance could not be determined since the exact length of the image of the Bismarck would not be known. It is not very likely that a subject will be exactly square to the line of sight from the camera in a photograph, so we have to use another component whose size is known, preferably a vertical measurement that would not be affected by the orientation of the ship.

In this case, we will use the height from the level of the sea to the top of the rangefinder on the tower mast, which measures 0.60 inches. We take the ratio of the horizontal distance across the photograph (9 inches) to the measured height of the tower mast (0.60 inches) and multiply that by the actual height of the tower mast (110 feet), and we get 1650 feet as the field of view.

As you can see, the result is almost identical. The angle of view is actually circular, so to be precise, we have to determine the diagonal of the 6-inch x 9-inch picture, which turns out to be 14.1 inches and represents the diameter of the circle. That equates to an overall field of view of 2580 feet. We take half of that measurement (1290 feet) and divide that by the tangent of half of the angle of view of 46 degrees (0.424).

We then get 3040 feet (1010 yards) as the distance to the Bismarck if the picture had been taken with a 50mm focal length lens. If the picture had been taken with another lens, we would have to divide 1290 by the tangent of half the angle of view of that lens to determine the distance to the ship.

I hope that this explanation clarifies the issue for you and possibly others who don’t quite understand the methodology. If you still have any questions, please post them.

Best regards,

Bob

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Photography

Post by Bill Jurens » Fri Feb 10, 2006 3:35 am

It is worth noting that when examining prints of poor quality photography -- which this certainly is -- it is generally impossible or at least very difficult to determine whether a change in image size is due to a change of lens or a change in enlargement made in the darkroom. My guess is that the changes in image sizes noted here stem from work in the darkroom rather than an on-the-scene lens change. Of course if one has the negative(s) at hand, such ambiguity disappears.

Some time ago, I did a rather complete analysis of NH69722. My conclusions were that "... it would appear most probable that the range to Bismarck in this photo would be in the vicinity of 2500-3000 meters. Until and unless better photography can be provided, it is unlikely that this estimate can be significantly refined. "

There may be some value in examining the 16mm film footage of the action, as duplicates in such cases are virtually always contact prints, thereby preserving the negative and making photogrammetric analysis much easier. In fact, if distances to Bismarck are being sought, it is likely that the 16mm film footage -- if and only if the original filmstock can be examined -- will be able to yield much more useful values than an examination of enlargements from (presumably) 35mm negatives.

Bill Jurens.

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Negatives and films

Post by Antonio Bonomi » Fri Feb 10, 2006 11:17 am

Ciao Bill, Bob and all,

the discussion is really interesting and you know I spent lot of time as well on this subject.

YES, the Nh 69722 distance evaluation is on that range.
We should be all in agreement now.

Last year I went to Bundesarchiv in Koblenz, and on the main entrance they show all the material used thru the years by the war reporters.

Among many camera's what I noticed was that the film camera they were using used the same photo camera size film, so 35 mm as well.

This means that if ever we will be able to find the original battle film, we are going to have thousands of photos out of those negatives.

Just a curiosity Bill, why do you think it was a 16 mm film ??

The many photos I have of PK people working with Film camera on KM warships ( BS, TP, HP and PG to name few of them ) shows the utilization of that 35 mm film.

Here some examples :

http://www.forum.marinearchiv.de/viewtopic.php?t=1225

Ciao Antonio :D

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Post by Robert J. Winklareth » Fri Feb 10, 2006 6:52 pm

Hi all,

In his posting of 7 February, Antonio stated that the photographs shot by Lagemann were very likely taken with a 50mm fixed focal length lens using a Leica or similar camera that was standard equipment in the Kriegsmarine. All lenses at the time were fixed focal length lenses since zoom lenses with variable focal lengths did not become generally available until long after World War II.

Antonio goes on to say “Please do not imagine that 65 years ago they had photo cameras that were so easy to change the lenses, not surely like recent standard photo cameras where you had fast changes possible.” That statement is entirely false and misleading as to the capabilities of cameras at the time.

Please be advised that:

a. Leica and Zeiss Contax, the two leading 35mm cameras at the time, were specifically designed with focal plane shutters built into the body so that they could readily accommodate interchangeable lenses.

b. The Leica and the Contax were introduced in the early 1930;s, some 70 years ago, and by 1936, both had as line of interchangeable lenses encompassing over six different fixed focal lengths ranging from 28mm to 400 or 500mm in size.

As a user of a pre-war Contax III camera for over 25 years, I can attest to the fact that the various lenses were just as easy to change as they are on the most modern cameras of today. All you had to do was line up the red dots on the camera and on the lens, insert the lens into the body, and give it short clockwise twist until it was locked in place. It could not have been easier. An accomplished photographer like Lagemann could probably have done it in 5 seconds or less.

Since the 28mm fixed focal length lens was available for both the Leica and Contax by as early as 1936, it must be considered as a candidate for taking some of the pictures of the Bismarck during the operation. A 28mm lens would place the Bismarck at a distance of 1330 yards in NH69722, which is very close to the 1275 yards shown as the separation between the Bismarck and the Prinz Eugen at 0556 in Antonio’s official large-scale diagram of the tracks of both German ships.

Antonio has still not explained the discrepancy between the 2400 yards or so currently being advanced by him as the distance to the Bismarck in NH69722 versus the 1275 yards separation at 0556 in his official diagram. We need a credible explanation for that discrepancy so we can determine the focal length of the lens that was actually used to take NH69722 and try to validate the methodology described herein for determining distances to ships by photo analysis. I hope that Antonio will soon be forthcoming with that information.

Best regards.

Bob

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Photo distances

Post by Antonio Bonomi » Fri Feb 10, 2006 9:00 pm

Ciao Bob and all,

you can very easily check yourself the angle of the lenses used by Lagemann to take the Nh 69722 ( first salvo ) photo.

Just measure as I did the plates on Prinz Eugen turrets, put the correct Lagemann distance from them on the 105 mm A/A platform and you will realize that the angle is 45 or 46 degrees, so it was a 50 mm lens, just as you wrote as well some days ago.

Just use the dedicated post on this forum and it will be easy with trigonometry.

Can you explain with your photographer skill the reasons why Lagemann should have changed his lenses on that situation ??
Why a 28 mm ?? Why not a zoom ?? Why not leaving there is best solution with the standard 50 mm he was already using ??

Both ships went zig-zag to avoid fall of shells for sure, unfortunately we do not have yet the film, nor photos of that battle minutes from 05.56 till 06.04.

What we have is that painture, and we know now were Bismarck sailed, on Prinz Eugen starboard side faster than Prinz Eugen probably 30 or more knots versus 27 knots of the cruiser.

Now I am not in condition to put 2 exact measures of the distances at 05.56 and at 06.04, but only some estimations with obvious tolerances.

At 05.55 Bismarck was at 2300-2700 meters from Prinz Eugen.

At 06.04 Bismarck was at 1400-1600 meters from Prinz Eugen.

So lets use to make it easier the 2 average measures, 2500 and 1500 meters ( in my personal opinion as I wrote the Bismarck was at 2300 meters on Nh 69722 ).

Anyway, that will mean a gain of 1000 meters on 9-10 minutes by Bismarck on Prinz Eugen which is possible as you know well due to the speed delta of 30+ knots versus 27 knots even if they went straight and to me that was not the case because under enemy fire.

Ciao Antonio :D

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Post by Robert J. Winklareth » Fri Feb 10, 2006 9:17 pm

Hi Bill Jurens,

It is interesting to see that you came up with a distance of 2500-3000 meters (2750-3300 yards) for the separation between the two German ships in NH69722. After correcting for obvious cropping, resizing to 2 x 3 format, and accounting for final trimming of the book containing the photograph, I arrived at a figure of 2700 yards using my methodology. I am curious as to what methodology you used in coming up with the range of distances after your complete analysis of NH69722.

I believe that Antonio may have misinterpreted your comments. You were obviously referring to the 16mm battle film separately from the prints derived from the 35mm still pictures. I agree with you that the 16mm film footage would probably make photogrammetric analysis much easier.

At least we would not have to worry about the possibility of interchangeable lenses being used, although some film cameras were equipped with a turret for three different focal length lenses. If the resultant images represent the entire frame from 16mm film, and if we knew the focal length or angle of view of the lens used, we would have sufficient information for a reasonable analysis.

Best regards.

Bob

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Film and photo camera's

Post by Antonio Bonomi » Fri Feb 10, 2006 9:23 pm

Ciao Bob and all,

probably you better look carefully into this link to see the original equipment used both for film and photos.

http://www.forum.marinearchiv.de/viewtopic.php?t=1225

Ciao Antonio :D

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Photogrammetry, etc.

Post by Bill Jurens » Sat Feb 11, 2006 7:48 pm

My analysis of NH69722 used a variety of methods. One of these involved comparing the relative size of Bismarck to that of various and sundry foreground objects after resecting for camera position. This resection checked for a field of view equvalent to a 50mm lens, which is one reason I believe the double-page spread as printed in the World War II book is essentially a full frame print. Once one has this, one can also reconstruct the principal point and to additional measurements from there. The quality of the photography is so poor that no one method is likely to be conclusive, but several independent techniques which seem to close upon a close range of figures and which do not uncover obvious inconsistencies would seem to be fairly reliable.

I utilized other "extra-camera" methods as well. These are independent of the geometry of the camera itself, and depend solely upon the relationships of the object to the background, etc. In general, if the object is in front of or behind the horizon, the vertical position of the 'cut line' of the horizon across the target can give in and of itself provide a fairly good estimat of range. In addition, one can measure what amounts to the dip angle, which is the represents the anglular distance between the horizon and the 'foot' of the target, and the relative offset of various parts of the target from the principal point, which can sometimes be recovered via careful resection of the projection of surfaces which are known to be perpendicular to one another.

J.C.C. Williams' (excellent but difficult-to-find) "Simple Photogrammetry" describes a variety of other techniques which might also be applied.

Antonio may well be right in assuming that the motion picture film was exposed on 35mm rather than 16mm stock. If so, the photogrammetry will be so much the better. I assumed the motion picture was 16mm because I had a hard time picturing the Germans setting up a 35mm camera installation on what must have been fairly short notice in probably a fairly exposed position in order to film a naval battle in 'real time'. Having someone peek out a hatch with a hand-held 16mm camera is one thing, but setting up a full 35mm motion picture camera setup, which would almost certainly require a tripod and at least one assistant probably in a fairly exposed position is something else entirely, especially if combat (along with the probablility of high-speed and unpredictable maneuvering) were to be expected.

The focal length of the lens used to take the photograph is more or less irrelevant if all one has to view are paper prints, simply because it is so often (and so easily) modified in the darkroom during enlargement.

Bill Jurens

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Post by Robert J. Winklareth » Sat Feb 11, 2006 10:07 pm

Hi Antonio and all,

I hope the you, Antonio, realize that your persistence in claiming 2500 yards as the distance to the Bismarck in Photo NH69722 is tantamount to an admission that the 1275-yard separation between the Bismarck and the Prinz Eugen depicted in your “official” diagram of the relative tracks of the two German ships is in error. And not just a minor error of one or two or even ten percent, but a whopping error of nearly 100 percent.

By proclaiming that the Bismarck was actually nearly twice the distance away from the Prinz Eugen at the beginning of the battle, you have now raised serious questions about validity of your reconstruction. Your “official” version of the battle already stretched its credibility to the maximum in view of the physical limitations involved, but your new figure of 2500 yards puts your reconstruction far beyond the realm of possibility.

Your “official” diagram places the Bismarck some 1340 yards astern of the Erinz Eugen when she crossed the track of the Prinz Eugen to return again on the port side of the cruiser at 0608-1/2. All of the gyrations that you put the Bismarck through, turning to starboard and then sailing around behind the cruiser, actually made the Bismarck loose ground from the separation of 1275 yards that existed at 0556.

You never did explain how the Bismarck could have come abreast of the Prinz Eugen from a distance of 1340 yards astern of the cruiser in only half a minute from the time of 0608-1/2 until 0609 when the battle ended. Now you have increased that distance by another 1225 yards by putting the Bismarck that much further away at the beginning of the battle.

Let’s make sure that we understand the geometry of the situation. At the beginning of the battle, the Prince of Wales was at a bearing of about 140 degrees from the German squadron, which was traveling on a baseline course of 220 degrees. Photos NH69729 and NH69730, as well as the uncataloged broadside view of the Bismarck and Lt. Schmitz’s sketch, all show the Bismarck’s guns trained somewhat forward of her port beam.

With the Prince of Wales turning away at 0605, the line of sight from the German ships became almost perpendicular to the baseline course of 220 degrees. According to the first gunnery officer aboard the Prinz Eugen, the Bismarck came into his line of sight to the Prince of Wales just before the Prinz Eugen ceased fire at 0609 in compliance with the order not to shoot over the Bismarck.

In the past, some have tried to argue that by both ships turning in the same direction, the Bismarck could have been seen abreast of the Prinz Eugen without actually having passed the cruiser. While this is true, such a maneuver would not place the Bismarck in the Prinz Eugen’s line of sight to the Prince of Wales, so let’s keep the discussion within the realm of the actual circumstances.

There is no ambiguity about the Bismarck being directly in line between the Prinz Eugen and the Prince of Wales at 0609, and there can be no question that the actual distance that the Bismarck would had to have made up on the Prinz Eugen was 2565 yards (1340 yards + 1225 yards). With a speed delta of 3.0 knots (100 yards per minute), it would have taken the Bismarck more than 25 minutes to come abreast of the Prinz Eugen, long after the battle was over.

Do you, Antonio, have any explanation for this major discrepancy in your “official” diagram of the battle? Can you come up with a new diagram of the tracks of the Bismarck and Prinz Eugen using the new distance of 2500 yards for the separation at 0556? How does this affect your presentation in “Storia Militare”?

Best regards.

Bob

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Post by iankw » Sun Feb 12, 2006 12:17 am

Bob, I am no expert on Antonio's maps because, to me, it is unimportant. I know it is important to others, and I'm fine with that but I am never likely to write a book about it so, as I say, to me it is unimportant. However, there are things I have picked up in reading all the descriptions, looked at all the charts etc and one thing even I know is that PE made more turns than BS. This has two effects to my limited knowledge:

1) PE will travel a smaller distance along the main course during the same period of time.

2) Ships slow down when they make turns.

I stand to be corrected on this but I know you have asked this question before and, to my knowledge at least, noone has ever pointed out these two simple facts. As I say I stand to be corrected.

regards

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