the frame sequence and, thus, overlap. Film flattening was
effected by the action of the dynamic pressure built up in
an outboard tube,
The camera mount, consisting of a tubular gteel frame, permitted
both drift correction and tilting up to 47 from the horizontal.
The advancements made in the following years were principally
directed at automating the operating cycle and improving
optical performence, The latter was mainly achieved by the
designing of special lenses having, by the standards of the
time, low distortion and low field curvature, In addition,
the RMK C/2 developed in 1925 already had a detachable finder
scope. Other improvements over the earlier model were the
210mm f/4.5 lens, selectable shutter speeds of 1/75, 1/100,
1/130 and 1/160 s, and a frame counter,
The RMK C/3 manufactured in 1926 already had a square image
frame of 180 mm x 180 mm, which later became the standard
international format, The lens was a 210mm f/4,5 Orthometar,
In parallel with the continuous improvement of the serial
cameras, Jena also advanced its manually operated single-shot
cameras, with both plate and film magazines. Mentioning each
and every model here would, however, exceed the scope of this
report.
Another essential innovation was introduced in 1928 with the
RMK C/5-Perseus (Fig.5). It was the first camera to have a
control unit for drift correction and overlap control by
means of a travelling grid and a course line visible together
with the ground image on a ground-glass screen, An upgraded
version designated C/5a (Spica) was driven by a 12V, 100W
d.c. motor.
From 1928, the Jena works designed and built various models
of two-channel mapping cameras as well a four-channel one,
the AxRMK C/1, Their internal parameters were based on those
of the respective single-lens cameras from which they were
derived, For their technical data see ref. /1/.
The continuous advancements were frequently stimulated by
the practical requirements of the users, One such requirement,
the free selection (within certain limits) of the flying
height at a given photoscale, led to an innovation in the
first half of the thirties automatic high-precision cameras
with interchangeable lens cones of different focal lengths.
The RMK S 19819 (Fig. 6) with the standard 180mm x 180 mm
frame size, for example, was available with 135mm, 210mm,
300mm and 500mm lens cones, An electric drive module with
multistep gear, finder scope or ground-glass viewfinder could
be fitted,
The development of peripheral modules such as the horizon
chamber (for the 210mm lens cone) for determining photo tilt,
and the statoscope recording chamber aimed at a further
enhancement of performance capabilities and operating con-
venience,
The introduction of the travelling grid, which moved acrosss
the ground-glass viewfinder at infinitely controllable speeds,
62