= 25 + 
FILM FLATTENING 
  
Film flattening is an important step in serial 
photography. Possible solutions are indicated in [44], 
and the pneumatic method using over-pressure is discussed 
there in more detail. This method is employed in the two 
cameras which took the photography used extensively in this 
paper for the demonstration of sources for image geometry 
changes, 
Another solution, mechanical flattening by pressure, 
which has been and still is employed in English cameras, 
is described in [15]. 
Film flattening with the pneumatic method using over- 
pressure ean be summarized as follows: 
- the aerial film is brought into position in front 
of a reference plate which forms part of the magazine, 
a vacuum is then created between the back of the film 
and the plate by removing the air through channels 
in the plate connected To a vacuum pump on a Venturi 
tube, 
- the plate, together with the attached film, is then 
pressed against a frame defining the image plane. 
The process contains a number of sources for deviations 
of the light-sensitive material from the image plane. 
- deviation of the image frame from a plane 
- unflatness of the reference plate