A very short history of Gamma in video. In 1936 the BBC was the first organization to deploy a clear gamma = strategy in broadcasting. They first applied a gamma amplifier located = after the video switcher. All camera outputs and all monitoring scopes = worked with the raw video signal from the emitron tube cameras (similar = to iconoscope design) which had a 1:1 output signal correlation to the = light input. =20 Within the first year of operation the BBC radically modified their = gamma deployment strategy. They removed the special gamma amplifier = from the switcher (vision mixer) output and relocated the gamma circuit = to the video amplifiers in their emitron cameras. =20 What they knew at the start: The gamma circuit corrected the camera output to correspond to the = response characteristic of the CRT control grid design. When the video signal is converted from its raw form to the gamma = modified form (approx .45) the atmospheric noise of the OTA transmission = becomes evenly distributed across the luminance range. =20 What they gained by moving the gamma function to the camera. The monitoring scopes provided a representation of the camera output = signal that was much easier to interpret. =20 Camera shading/matching became easier to accommodate with the improved = signal monitoring. The vision mixer function was improved as the signals could now be = "linearly" blended with faders. =20 Much of this development work is attributed to Alan Blumlein who was the = tech lead at the London Station. Pete Fasciano =20 Fellow, Advance Development =20 Co-founder, Avid Technology =20 1925 Andover St. B2-3 =20 Tewksbury, MA 01876 =20 Ext: 978-640-3308 Fax: 978-640-3116 peter_fasciano@xxxxxxxx -----Original Message----- From: Henry Baker [mailto:hbaker1@xxxxxxxxxxxx] Sent: Tuesday, January 18, 2005 12:47 PM To: Allen Le Roy Limberg Cc: opendtv@xxxxxxxxxxxxx ---------------------------------------------------------------------- You can UNSUBSCRIBE from the OpenDTV list in two ways: - Using the UNSUBSCRIBE command in your user configuration settings at FreeLists.org - By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word unsubscribe in the subject line.