Raster bars. Remember ‘em? You’d see them on televisions and computer CRT’s that were in operation in the background on your own TV screen. The raster bar was the break or leading edge of the refresh scan on the tube. You could see them because the recording medium and the scan rate of those TV’s and CRT’s were operating at the same frequency (60Hz, I assume) and out of phase. The recording device would take a “snapshot” which would catch the raster bar in mid sweep and you’d see it as an angled black line across the screen of those other displays.
What I wanna know is, why do you rarely see ‘em anymore? Do the new digital recording devices somehow eliminate them? Or are recording devices, televisions and CRT’s all operating at different refresh frequencies these days?
most professional cameras today have a feature that allows the operator to synchronize the frequency of their camera to that of the monitor in frame.
i find that most monitors are at 75.1Hz or 85.1Hz, and can synchronize my camera nicely. but sometimes the monitor frequency is too low, and i can’t get a proper sync.
It just seems like TV techs hate to see them. So they either set up the shot so you can’t see the screen, or they carefully sync up the camera and the monitor to eliminate the bars.
In the past, they may just have tolerated them more.
Any Spider Robinson fans out there? This is not a hijack question, well, not too much anyway.
In Robinson’s book Lady Slings the Booze, the character telling the story in the first person uses several names, one of which is Ken. He is also plagued by people thinking he resembles a famous newscaster, who is never actually named. A lot of plot twists later, one of which involves the frequency to a remote control bomb, at the end, he hears that the newscaster was beat up by some guy asking him “what’s the frequency Kenneth?”
I wrote to Robinson after I read that to ask if he did mean Dan Rather was the unnamed newscaster. He was kind enough to write back and tell me I was correct, and that I was the first to have guessed correctly. An all around nice guy.