(1) The two most commonly used tubes are the various versions of the
Plumbicon and Saticon tubes.
The diode gun pickup tube is an improved
Plumbicon tube. You may hear of motre cons, which all try to minimize the
negative aspects of the camera pickup tube and maximize the positive ones in
order to produce optimal pictures in a great variety of production
conditions.
(2) Camera pickup tubes come in four formats, which actually refer to
the diameter of the front surface of the tube. Thus we have 30mm (1.2-inch)
tubes; 25mm (1-inch) tubes; 18mm (2/3-inch) tubes; and 13mm (1/2-inch)
tubes. The 18mm and 13mm tubes are almost always referred to as the 2/3-
inch and 1/2-inch tubes.
Large studio cameras usually have 30mm or 25mm
tubes. Most ENG/EFP cameras that use a pickup tube as an imaging device use
small 2.3-inch format.
Some ENG/EFP cameras, especially the camera-
recorder, use 1/2-inch tubes.
(3) Why so many formats?
All other things being equal, the larger
format tubes (tubes with a large front surface) produce higher quality
pictures than the 3/4-inch tubes.
You many want to compare the various
pickup tube formats to the size of a film negative. A 35mm film generally
produces a sharper picture than a 16mm film which again is superior in
quality to a super 8mm film. However, constant efforts are being made to
manufacture small-format tubes that produce high quality pictures.
(4) The CCD is radically different from the camera pickup tube.
Whereas the pickup tube utilizes an electron beam that scans a light-
sensitive photoconductive target to produce the video signal, the CCD has a
great number of image-sensing elements that transfer an optical image into
many spots carrying an electric charge.
These charges are temporarily
stored and then translated line by line into a video signal (voltage). The
major advantage of the CCD over the tube is its small size.
TV cameras
using the CCD as an image device are considerably smaller than even the
smallest ENG cameras using a pickup tube. So far, the major disadvantage of
the CCD camera is that it does not produce the high-quality pictures
produced by cameras that use pickup tubes as an imaging device.
d. The electronic characteristics of a camera depend primarily on the
performance of the imaging device used.
However, the camera incorporates
certain electronic equipment and controls that either boost the positive or
minimize the negative aspects of the imaging device. Because the electronic
characteristics of the camera influence many other production aspects such
as lighting, graphics, and what people should and should not wear, we will
take a brief look at color response, resolution, operating light level, and
contrast.
(1) Color response. Ideally the camera should respond to all colors
alike. However, this is not the case. The Plumbicon tube, for example, has
had a continuous battle with the color red. Red produces not only a weak
video signal but also a fuzzier image than other colors. Improved Plumbicon
tubes, and especially the Saticon, are designed to treat all colors as
equally as possible. In an inexpensive color camera you can use the same
type of vidicon tube for all three chrominance channels. This is why the
color response in less sophisticated cameras is not "true" - that is,
certain colors do not reproduce exactly like the original color in the
scene. High-quality color
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