After WWII the Americans & British sent a team into the Leitz factory in Wetzlar to examine construction techniques of the Leica camera. The British party took away the Leica IIIb drawings & then produced the Reid camera to that design. Taylor Hobson manufactured the lenses and Sigrist & Reid the body. This is the account of their findings. :
B.I.O.S. FINAL REPORT No.1436
THE "LEICA" CAMERA
"This report is issued with the warning that ,
if the subject matter should be protected by
British Patents or Patent applications , this
publication cannot be held to give any protection
against action for infringement ."
BRITISH INTELLIGENCE OBJECTIVES SUB-COMMITTEE
TABLE OF CONTENTS
THE "LEICA" CAMERA
Purpose of investigation................... 1
Details of journey......................... 1
General description of factory............. 2
Leica Camera - Manufacturing Processes..... 3
Machine Tools and Methods.................. 3
Cutting Multiple Threads................... 4
Optical Manufacture........................ 5
Satin Chrome Finish........................ 5
Assembly and Testing....................... 6
Shutter Timing............................. 6
Shutter Blinds............................. 7
Lens Flange................................ 7
Setting Telemeter.......................... 8
Testing of Lenses.......................... 8
Final Test................................. 8
Drawing Office............................. 8
Research and Development................... 8
Working Hours.............................. 9
Production Costs Etc....................... 10
Other Products............................. 10
General Conclusions........................ 11
Appendix "A" . Works Notice........... 12/13
Appendix "B" . Wage-Groups with Age-Gradings
for Men and Women...... 14/15
Subject Index.............................. 16
PERSONNEL of TEAM
THE "LEICA" CAMERA
Mr. H. J. Bigg.
BIOS Trip No:- 2858
BIOS Target No:- 9/14
Dates of Investigation.
BRITISH INTELLIGENCE OBJECTIVES SUB-COMMITTEE
1. The purpose of the investigation was to examine the
methods of manufacture and constructional details of the Leica
Camera with particular reference to finish, assembling and
testing. It was not intended that the team should cover the
manufacture of the lenses, although some details of the
construction of lenses were noted and are included in the report.
One member of the team examined the microscope manufacturing
side of the business but was unable to add any useful information
to that already obtained.
Details of Journey.
2. The Team left England on the 15th November, 1946 and
returned on the 28th November, 1946. Of this period only that
from the 18th to 26th November was spent in Germany and the
investigation at the Leitz Works was carried out on 19th, 21st
and 22nd November. Subsequent visits to the Leitz works were
made by the Leader and one member of the team on the 25th and
26th November to collect documents for the removal of which
permission had to be obtained.
3. Close co-operation with the U.S. Scientific Consultant
Section was necessary and it was considered advisable that the
team should be accommodated at Hoechst, near F.I.A.T. Head-
quarters, and proceed by road to Wetzlar for each day of
investigation. This proved to be a very happy arrangement
and cordial relations were established with the U.S. Scientific
Consultant Staff which were of inestimable value to both the
Americans and ourselves.
4. Before the investigation at the Leitz Works was
proceeded with the micro-films taken at the Leitz Works by a U.S.
Army Micro-film Unit, and filed at F.I.A.T. Headquarters, were
examined by one member of the team and it was soon established
that these films were, from a practical angle, completely use-
less. Although all drawings and documents at the Leitz works
had been filmed they had been so completely mixed up that it
would have taken a very knowledgeable Leitz executive many
months to sort out those relevant to the Leica Camera.
5. At a meeting with B.I.O.S. and the U.S. Scientific
Consultants Section it was agreed that the team should be author-
ised to remove copies of the drawings for the Leica III B and
III C or, alternatively, that another micro-film unit should be
sent to the Leitz Works to take a fresh set of films, under the
direction of a member of the Team. The U.S. Scientific Consult-
ants Section also indicated their interest in the investigation
at the Leitz Works and decided to send a team to join forces with
the British Team.
6. The investigation, therefore, proceeded as a joint Anglo-
American investigation although members of each team made their
own notes and reported to their own team leader. It is empha-
sized that this report is the result of the investigation of the
British Team and is not a joint report.
7. The British Team split at the works to cover various
fields such as machining methods, assembly, testing,inspection
and organisation. This report is a consolidated result of
8. The persons interviewed were;-
Herr Ernst Leitz (Senior). Chairman
" Ludwig Leitz Technical Director
" Dumur Commercial Director
and various members of the technical staff of
We received every help and courtesy from these persons and a
considerable amount of assistance from Mr. Dumur.
General Description of Factory.
9. The Leitz Factory, situated at Wetzlar, comprises a
number of buildings built over a period of years. In conse-
quence some of the departments are old-fashioned and badly
lighted whilst others, notably the new eight-storied building
standing in the centre of the factory site, are modern and well
10. The plant and equipment varies similarly but is all well
11. Besides the main Leitz works, the firm of W. & H. Seibert,
Instrument Makers, is owned by Leitz and they have a few
dispersal works for pressings etc.
12. As the chief employees of labour in this beautiful little
town, the Leitz Company can rely on continuity of service and
have adopted a very sound policy of training young labour from
apprentices. They take pride in the skill of their workers
and have welfare and other schemes which help to this end. As
a result there is a high percentage of skilled labour employed
and the general labour is highly skilled in the particular
Leica Camera - Manufacturing Processes.
13. The Leitz Company is now producing only the Model III C
Leica Camera, this having by development, superseded the
Model III B. The Model III C differs from the III B in several
aspects, although it is functionally similar. It is approx-
imately 1/8" longer, it has an integral top plate and range
finder cover, and the main body is now a single pressure die
casting, which together with two other pressure die castings for
the top and bottom of the unit forms a complete chassis for the
assembly of all the other component parts. In the later models
the focal plane shutter blind rollers have been fitted with ball
14. The outer case of the Leica although 1/8" longer is
formed from extruded tube as was the case in the III B and
15. The coupled range and view finder has not been altered
in any way.
16. Leitz make in their own factories practically all their
requirements, including the leather cases for cameras and
17. Of the items bought out, the castings come from Mahle of
Stuttgart, slow speed shutter mechanism from Gauthier of Calmbach,
shutter tape from Soenecker & Pfaff of Wupperthal Barmen, and
blind material from America through their associated company in
Machine Tools and Methods.
18. In the machine tool side the following machines were
noted:- Steinel Drilling Machines, Lindner Thread Grinder,
Deckel Engraving and Horizontal Milling Machines, Lorch Lathes,
Sooda Automatics, Mikron Gear Hobbers and Hauser Jig Borer.
The chasing lathes were by Hille.
19. The general machining of small precision parts followed
very closely the usual procedure in this country.
Cutting Multiple Threads.
20. The cutting of the multi-start thread in the focussing
mount of the Sumitar and the Elmar lenses was carried out on a
converted Lorch Lathe. The conversion of this machine by Leitz
was extremely ingenious. The component to be screw-cut was
screwed on to an attachment on the head-stock of the lathe by a
chucking-thread already cut in it. A single tool was employed
in the tool post. The whole head-stock was then caused to
oscillate backwards and forwards by a thread attached to the
back of the head-stock engaging with a chasing nut which was in
turn engaged and disengaged at the end of each stroke by a yoke
which also operated four glass-mercury switches. These
switches operated a solenoid attached to the drive counter
shaft which, in turn, operated a reversing clutch in the drive.
The head stock was caused to rotate for some ten revolutions
in a clock-wise rotation which moved it forward by the chasing
thread on it engaging with the chasing nut. At the end of
this forward stroke the chasing nut disengaged and then
re-engaged with the next thread, the counter shaft also re-
versing, causing the head-stock to rotate in an anti-clockwise
direction on the back stroke for some ten revolutions. As the
head-stock oscillated backwards and forwards at each successive
movement it engaged with a conveniently disposed paul which
engaged with a ratchet connected to the feed on the tool post
and at each backward and forward stroke the tool was automat-
ically fed in. The extent of this was shown by a clock
indicator attached to the tool post slide. The device worked
well and was almost "fool -proof" to operate.
21. The male 5 start thread was cut first on one lathe of
the type just described. The female member was cut in an
identical manner but to suit the male thread. A certain amount
of play was purposely left between the two, when dry, but after
both had been well washed out in paraffin a liberal application
of special grease was applied and they were assembled together.
The special lubricant caused them to have a very fine "velvety"
feel when moved in or out. As male and female members are
machined to suit one another it is very doubtful if any two
complete units are dead alike as regards inside and outside
diameters of threads. Mr. L. Leitz agreed that this was so
but added that once a lens focussing mount was assembled it
became a unit for good and it did not need to be interchanged
with parts from another complete lens mount.
22. The pitch of the 5 start thread in the focussing mount
of the Sumitar was 6.210 mms., but in the case of the Elmar a
pitch of 6.00 mms. and also 6.138 mms. was employed.
To ensure lineality between movement of the lens and the
coupled telemeter a slight cam is machined on the end of the
male member of the multi-start thread which engages with the
roller which actuates the swinging prism of the telemeter. The
greatest depth of this cam face does not appear to exceed .007".
23. The manufacture of small prisms as used in the tele-
meter were by mouldings cemented in fours and then gang-milled
by diamond milling tools. They were then taken apart and
milled to the other face. Diamond tool milling machines are
used for slotting the hypotenuse. Smoothing and polishing was
achieved by normal type poker-arm machines. Edging was carried
out on small lens in the telemeter by diamond wheels. These
wheels are made for Leitz by Jung of Berlin.
24. The small reflecting mirror in the range finder is very
lightly alluminised, the degree of deposit being just sufficient
to give an equal degree of brightness to both the directly and
indirectly received images when seen through the range finder
25. The satin-chrome finish on external metal parts was
obtained by the following process:-
26. Sandblast, hot cleaner without current, cold cleaner
with current, warm rinse, followed by cold rinse, hydrochloric
dip, copper flash, cold rinse, sulphuric dip, cold rinse, bright
nickel-plate, warm rinse, hydrochloric dip, bright chrome,
drag-out rinse, cold rinse, hot rinse, and dry.
27. All articles were jigged on racks and the racks were
screened to obviate side-throw.
28. The bright nickel tank was approximately 6' x 2' x 21/2',
six depolarised anodes being employed. The volt-meter and
ammeter on the resistance control board were all moving
coil pattern and the tank was worked at 2 volts, 25 amps. No
agitation of the electrolite was employed.
29. The chrome tank was approximately 4' x 2' x 21/2', twenty-
eight strip anti-monial lead anodes being employed. Moving
coil volt and ammeters were also fitted in the resistance board
and the tank was worked at 51/2 volts, 300 amps.
30. It was particularly noted that the time allowed for a
satisfactory chrome deposit was exactly three minutes. All the
plating equipment was spotlessly clean.
Assembly and Testing
31. The Model III C takes longer to assemble than its
predecessor, 33 hours as compared with 29 hours, but there is no
doubt that as an engineering job it is far superior.
32. Sub-assemblies were batched in tens and assembly practice
was very similar to that employed in most instrument factories.
Special jigs, fixtures, and tools were employed where-ever
possible to assist rapid and accurate assembly. Female labour
was used for the minor assemblies, the male labour being
employed mainly on shutter and range finder assemblies and on
33. The main design of the shutter is in no way basically
changed; only slight modification of various components to
suit the new assembly. In the assembly of the shutter fast-
range escapement one component after another was tried till one
was found that worked in a fairly satisfactory manner and then
various minor alterations were made to it by filing, and in
some cases, a light tap with a small watch-makers hammer. The
skill of the operators was undoubtedly the chief asset in the
efficient assembling of this shutter.
34. The slow speed escapement of the shutter is made by
Gauthier of Calmbach.
35. The timing of the fast range of the shutter is carried
out with the aid of a stroboscope of somewhat antique design.
By means of this the 1/200, 1/500 and the 1/1000 speeds are
checked. The stroboscope consists of a revolving drum placed
horizontally, with 33 horizontal slits in its surface,
illuminated from inside by a lamp of approximately 20 watts.
The drum is driven by a belt from an electric motor which may
be controlled by a rheostat. The drum is also coupled to a
speedometer in order that its speed may be set. The correct
speed for the drum to rotate at was 280 r.p.m. The camera
is held on a wooden block in such a manner that the light
from the rotating drum falls on the blinds of the focalplane
shutter. The shutter is then fired and a series of
stroboscopic lines are seen in the aperture. If the shutter
is correctly set these lines appear vertically but if the
shutter is incorrectly set the lines will curl down either to
the left or to the right according to whether the shutter is set
too slow or too fast.
36. The checking of the lower speeds was only carried out
on the 1/20 second and 1/4 second settings by means of a
revolving series of lights. The various speeds of the shutter
were not accurate to the measurements on the shutter control
knob and this fact was acknowledged by the Leitz executives.
who pointed out, however, that the results obtained were quite
good enough for all general requirements.
37. A metronome was used in checking the one second
38. The fixing of roller blinds and tapes on the focal-
plane shutter was carried out on a very ingenious fixture.
The body of this fixture is all metal and accommodates the
two roller blinds and tapes on pivots ensuring that the blinds
and tapes are of the right length and fixed at exactly the
right distance apart. After the blinds and tapes have been
stuck to the rollers they are allowed to dry for at least
48 hours before being assembled into a camera. In every
possible operation special jigs and fixtures are used to
increase speed and uniformity of production.
39. The checking of the lens flange of the focalplane for
squareness is carried out by a focalplane collimator which is
located by the lens flange and directs a beam of light on to
a polished reflecting surface which is located on the focal
plane. Lack of squareness and an accurate measurement of the
extent of the error is at once visible on the graticule of the
collimator. When correction is necessary a specially adapted
vertical milling machine is used to correct the orientation
of the base of the camera body which corrects the lens flange.
If small errors in squareness occur which are not sufficient
to warrant machining, the lens flange is packed with a small
shim. The correct distance from the front of the lens
flange to the film pressure plate, located at the back of the
focal plane is 28.80 mms. which is the equivalent to 1.134".
40. Checking of the measurement was made by a special fixture
and a clock indicator.
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Camera Repairs & Restoration , Luton , England
Leica Repair Price guide
B.I.O.S Report Continued
Optical Dictionary - Lens Info