If you are less than 25-30 years old, you probably don’t know what I am talking about, but before 24/7 cable TV, television stations went off the air at about 2:00am, and broadcast a test pattern of circles and lines , accompanied by a an ear-splitting sine wave tone. This pattern usually had an image of an Indian in a full feathered headdress. Well, I woke up this morning at 4:00am, and the local independent station apparently goes off the air on Sunday mornings until 6:00am, and lo and behold, there is the indian head test pattern I remember from my youth (though without the audio tone), complete with the familiar Indian head.
I did a little googling, and the best I could come up with was that it originated from the 1939 RCA TK-1 monoscope test pattern generator, but why it had an Indian instead of, say, a bald eagle or a Hudson Terraplane, was never revealed. Can anybody shed some light on why there is an Indian on my test pattern, or better yet who he is?
This is a guess, but the graphic artist assigned to design the test pattern probably looked in his collection of graphic pictures and found a picture of an indian that fit the above description
Maybe the designer thought it looked good. Why is there a girl playing tic-tac-toe with a clown on British test patterns? (Yes, I know the girl is the daughter of the test patterns’ designer. That doesn’t explain why she’s playing tic-tac-toe with a toy clown.)
This board is really good - answers even before posting the question! I was just wondering last night what test patterns were used outside North America. (I have the Indian-head pattern as one of the wallpapers on my PC.)
I did speculate that the BBC might have used that same pattern, but with Queen Victoria instead of the Indian.
Just to follow the highjack, bbeaty, mandrills have nice colours, and the Utah Teapot was one of the first 3D models ever (by the Evans and Sutherland lab, IIRC). It was used as a benchmark/test case for quite a while.
I couldn’t find this question answered in that FAQ; I’m sorry if I missed it. What’s the point of these test patterns? Were they so older televisions could be checked to make sure they were working properly? Could they be adjusted? Or were the patterns just for the broadcasters to test their equipment?
The lines are at different thicknesses and angles so you can adjust your TV sharpness controls. The shades of grey are so you can adjust the brightness and contrast. The colours are there for altering the colour. The boxes and lines are so you can adjust the horizontal and vertical holds.
Basically, they’re standard pure and sharp images for adjusting your own monitor - much better than a moving image that may or may not be pure of line and colour in the first place.
Guanolad, I remember from back in the day in Australia, we were occasionally given a British test pattern which had lots of grey-scale and contrast boxes and devices surrounding a photographic picture of a little girl holding a clown doll. Much more common, however, was the local Australian test pattern which had no photographic image at all, and therefore allowed a wider range of contrast, tone, and colour test areas within the pattern.
I’ve often wondered which, from a technical viewpoint, was the better of the two.
I’ve seen the test pattern without the girl when I’ve visited and workd on TV shows. They use it for their own internal monitors and stuff. I guess there isn’t a real preference for either, as long as there’s an internal standard.
There are laws (well, FCC rules and regulations) concerning the quality of the transmitted TV signal. It is necessary to have an engineer onsite at the transmitter at all times to ensure the signal quality.
The use of a test pattern allows the station to transmit without an engineer onsite, because she can REMOTELY analyze the signal quality.
Some elements of the patterns are meant for the naked eye. Using the convergent lines, such as on the “bowties” on the corners of the Indianhead pattern, you can analyze the vertical and horizontal resolution of the transmitter AND of your receiver by discovering at what point the lines melt into an inseparable blob.
Other elements are judged on oscilloscopes. A vectorscope has a small box where each color should register. If the scan does not hit within the box for red, for example, a camera alignment may be in order. Some grayscale patterns generate a linear staircase display on an oscilloscope. If the stair steps are uniform in height, then video response is linear and everything is okay.
My new computers also come with a diagnostics program that produces test patterns for the video monitor. The help file says the diagnostrics program is used by technicians to recalibrate the monitor, if needed.
