AT 
[ME ILE MEE 
cross is 2x2mm), the line sickness is 404m. The 
reseau grid was recorded on the 1.6mm thick glass 
and measured on the precise monocomparator (As- 
corecord of Zeiss Jena) with the accuracy greater 
than +1um. 
23 Fitting up the reseau plate to the camera body 
First of all we have to assume that the film active 
surface will be flattened on the exterior surface 
(surface with crosses marked on it) of the reseau 
plate in the camera. To record the sharp image 
existing in the camera fiducial plane, after inserting 
glass plate between the objective and fiducial plane 
one must shift fiducial plane away from the camera 
objective on Al — (n-1)d/n (where: n - coefficient 
of light refraction in the glass, d - thickness of the 
glass plate). If it would be possible, no other adap- 
tational changes in the camera would be necessary. 
In our Pentacon-Six and for our 1.6mm thick glass 
plate the above described Al value would be equal 
to 0.5mm (Al=0.5mm for d=1.6mm, n=1.5). But 
this means, that our glass plate should plunge into 
the camera metal fiducial frame by 1.6-0.5 — 1.1mm, 
what would involve a serious cutting of the very 
delicate and precise metal fiducial frame of the 
Pentacon Six camera. Therefore in our case the 
reseau glass plate was fixed in the camera in the 
most convenient position from the point of view of 
mechanical camera reshaping (fig.3). This resulted 
in the shift of the camera fiducial plane (exterior 
plane of reseau plate) not by 0.5mm but by 1.2mm 
away from the camera objective. 
advisable solutions solution employed 
b 
= b 
Alz 05mm | a | } 
rd 
ports = ..Mmmi*, * 6mm. 
= zz E 6mm = 
on . e t ccm 
——————— a oi 7A 
to objective to objective 
  
     
  
  
  
  
Fig.3 Fitting up the reseau glass plate to the camera: 
a) the camera original fiducial plane 
b) the exterior surface of the reseau glass plate (on 
which the reseau crosses are marked) 
The reseau glass plate was glued to the special 
metal frame. This metal frame was lain on 4 pins 
of @ = 1.5mm which were screwed to the camera 
metal fiducial frame (they can be regulated). Metal 
frame with the reseau glass is fixed to the camera 
body with 2 screws, what enables easy assemblage 
and disassemblege. The 4 pins ensure the stable 
position of the reseau plate in the camera and 
make the adjustment possible. 
     
2.4. The Further Camera Modifications. 
The mechanical assemblage of the reseau glass plate 
(1.6mm thick) to the camera body caused a shift 
of the camera fiducial plane (exterior reseau plate 
surface) by 1.2mm (fig.3) away from the objective, 
instead of 0.5mm (due to the glass plate). This will 
effect the position of the camera objective, which 
must be shifted by 0.7mm towards the fiducial frame, 
to enable the proper use of the distance scale 
existing in the camera. This was achieved by shor- 
tening (mechanical cutting by 0.7mm) of the metal 
cylinder assembling the lenses. The change of the 
objective position developed the need for adjustment 
of the ground glass surface of the camera viewfinder. 
It had to be shifted away from the camera body on 
0.7mm (this was ackieved using a spacer washer). 
In the Pentacon Six camera the film is pressed 
against the fiducial frame using flat plate contact 
spring, which is connected on the interior side of 
the camera lid. The spring is pushing film con- 
tinuously to the slide bearings on the camera fiducial 
frame. The maximum distance available between 
slide bearings and plate spring is around 1.5mm. 
After the reseau glass plate has been assembled 
this distance was reduced to 0.3mm, what is far too 
little for the easy shifting of normal film. To prevent 
the film deformations caused by too tight sliding, 
the whole lid of the camera (together with the plate 
spring) was displaced from the fiducial frame by 
1.0mm (the hinges and the lock were offset on 
1mm). To enable approximate exterior camera orien- 
tation in the field a circular level was attached to 
the camera body and a mark was introduced to the 
field of view of the camera view finder (it points 
out the direction of the camera axes). 
3. THE ADAPTED RESEAU CAMERA 
PHOTOGRAPHIC RESOLUTION 
The examination of the camera photographic 
resolution ranged over the pictures taken using: 
non-adapted camera and camera with the 1.6mm 
thick reseau plate, and using two objectives: normal 
angle Biometar 2.8/80 (for the f-stops: 2.8, 8, 22) 
and wide angle Flectogon 4/50 (for the f-stops: 
4, 8, 22). Pictures made without and with the 
reseau glass-plate were taken for this purpose on 
the photographic glass-plates TO1 ORWO. The 
greatest losses of the camera resolving power were 
noticed at the biggest entrance pupils of the ob- 
jective. For the normal-angle Biometar 2.8/80 at 
the relative aperture 1:2.8 the resolution without 
the reseau-glass was around 37 l/mm at the picture 
centre and 24.6 mm at the picture edges. The 
1.6mm reseau plate caused the drop of the resolution 
by 9.5 l/mm in the middle of the image field and 
by the 2.4 l/mm at the image field edges. Relatively