The 1948 Olympic Television Cameras
There has been some interest in the television cameras that were used for the 1948 austerity Olympics, so I have written some notes that may be of use.
Television in the Great Britain of 1948 was very different
from today and the importance of televising the 1948 Olympics could be
judged by the space reporting the televising of them in the BBC yearbook
of 1949, less than one page!
The BBC had 3 Outside Broadcast vans, or scanners as they were known,
available by the start of the Olympics on July 29, but only one of the
pre war vehicles and the new EMI CPS OB vehicle were used. [Pawley
404] Six cameras were deployed, three from each of the OB vans.
The second prewar OB van, MCR2, was covering the athletics from White
City on Thursday and then the test match from the Oval on the Saturday.
There was some exchange of cameras between MCR1 & MCR2.
3 types of camera were used:-
One 1937 Emitron, two of the improved 1937 Super Emitron and three of
the new in, 1948, CPS* Emitrons.
Recent information received, leads me
to think there were three Super Emitrons, two of the curved back style
and at least one of the square back style as illustrated below.
This is the Long Necked version of the Emitron from 1937. The Emitron cameras started life with the "short neck" tubes, and later they were modified to take the improved "long necked" tubes. The cameras now had a bulge at the front to accommodate the extra tube length. It had a sensitivity of the order of 2500 Lux @ f3. The Emitron tube with its spherical glass enclosing the large target meant that the lens was a long way in front of the target and this placed constraints on the usable focal lengths and the depth of field in particular. “The older cameras were used in the stadium as they require much more light for satisfactory operation” [BBC yearbook] | |
The Super Emitron had an Image Section in front of the target and this meant that the image from the lens was formed on this smaller photo target which was much nearer the lens thus removing many of the constraints suffered by the Emitron lenses. Additionally it was some 10 times more sensitive (200 Lux @ f2) enabling the use of telephoto lenses in poor light conditions. The Super Emitron tubes were retro fitted into 2 of the cameras and these had modified housings to accommodate the different shape tube. The bulge on the camera front now became a bulge on the side. It was necessary to rotate the whole tube to correct for the image rotation between the photo cathode and the target. It is not clear how many Super Emitron cameras there were, I have been able to identify 2 case styles, curved and square backed. (illustrated) |
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The CPS Emitron tube was of the orthicon class and the target
was at the front of the tube, optically good for the lenses. It
was scanned orthogonally from the rear so no keystone distortion
and it was also said that the CPS Emitron tube was free of the
shading problems of the Emitron tubes. The tube was even more sensitive
about 100 Lux @ f2 was required. |
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Both the Emitron and the Super Emitron tubes suffered from shading
(an effect similar to lens vignette or portholing, but much more
pronounced and unpredictable) and other spurious signals. Correction
waveforms had to be added to the picture signal to attempt to alleviate
the shading. These waveforms were called "Tilt and Bend" and
required frequent adjustment. Additionally because the target was
scanned from the side the beam that scanning the target had to have
corrections added to it to correct the distortion known as keystone
distortion. This 405 line image is before correction. |
Notes:- BBC OB vehicles had a designation number starting
with MCR1. MCR = Mobile Control Room. They were known informally as scanners.
The American term is "Remote Unit".