Oscilloscope's

Mark Monciardini · July 9th, 2003, 10:10 AM

Does anyone have any information or links on using an oscilloscope. Does anyone have a breif explaination on what it is used for? Should everyone use it?

Vladimir Koifman · July 9th, 2003, 10:12 AM

I believe Tektronix, the king of scopes, has some tutorials on its site.

Robert Knecht Schmidt · July 9th, 2003, 10:23 AM

Scopes plot the amplitudes of periodic electrical signals with respect to time, or with respect to each other in Lissajous patterns, or in a variety of other ways. So oscilloscopes permit for a visualization of something that you can't see--electrical voltage differences.

With regards to video production, a video engineer will use a waveform monitor to look at the video signal being recorded to ensure that the levels fall within certain tolerances. One can "see" the electrical video equivalent of light exposure by looking at a waveform monitor.

Ken Tanaka · July 9th, 2003, 11:31 AM

Mark,
I'm willing to bet a blank tape that you are actually thinking of waveform monitors and vector scopes rather than oscilloscopes. If so, these displays are used for color correction and are available in software form from within editors such as Final Cut Pro and Avids.

See the book "Color Correction for Digital Video" for more detailed information.

Robert Knecht Schmidt · July 9th, 2003, 03:56 PM

waveform monitor = oscilloscope

Mike Rehmus · July 9th, 2003, 09:20 PM

Well, as an ex-Tektronix salesman and repairman, I'll just mention that an standard oscilloscope isn't a waveform monitor. A waveform monitor is a specialized oscilloscope and is quite different in function from a waveform monitor or vectorscope.

It takes special circuitry to decode the NTSC waveform and allow one to make a full spectrum of measurements. It even takes a special trigger circuit to get the normal oscilloscope to display a full-field or line trace properly.

Do you need this measuring equpment? Depends on where your finished output will be shown. If it is destined for cable or broadcast, you almost certainly need to monitor the video as it leaves your editing system.

I do use a portable Leader waveform monitor in the field when I really care about the proper setup of the camera system. I also have a Tektronix 520A in the studio so I can take a look at the video I deliver to the dupe rack.

I find that the Canopus software waveform and vectorscope measurements are very accurate (they are digital, they should be. It's just some mathematics to generate the display.) But one has to have faith that the output will be no different than the digital data.

I found, for example, on the old Canopus DVRexM1 composite video output, that it is only 75% of normal amplitude as measured on a waveform monitor using color bars. Canopus has admitted that that spigot does not perform correctly. Fortunately the S-Video and DV outputs are spot-on.

Without checking the video, I would have difficulty getting television commercials accepted by the local Comcast tech center without having first set the levels by refering to the waveform monitor and vectorscope. And bumping the DV to BetaSP would be more difficult if the video were not to spec.

DV will generate some very out-of-spec signals. Especially, as I've found, if one generates artwork in Photoshop or Illustrator. You cannot depend on the built-in NTSC filters in Photoshop or Illustrator or After Effects to keep you out of trouble.

Mark Monciardini · July 10th, 2003, 12:13 AM

Thanks guys, this helps a lot. I will read that book!

Mark Monciardini · July 10th, 2003, 12:17 AM

Mike,

Can you tell me what Canopus software you are talking about?

Robert Knecht Schmidt · July 10th, 2003, 11:30 AM

Mark, I think Mike's referring to the built-in software vectorscope and waveform monitor in the realtime Canopus editing aps, e.g., the latest Rex Edit, Storm Edit, EDIUS...

Great post, Mike, BTW. Thanks.

Luke Gates · July 15th, 2003, 01:18 AM

you can use the oscilloscope (o-scope) to measure voltage levels (from DC to microwave), phase differences, signal presence (or absence) logic highs and lows, frequency response, distortion, and complex waveform analysis, to name a few.
And as all you are arguing a basic o-scope is not going to enable you to view any video signal. You would need more specific equipment if you will.

July 9th, 2003, 10:10 AM	#1
Mark Monciardini Regular Crew Join Date: Jul 2003 Location: Salt Lake City, Utah Posts: 158	Oscilloscope's - why do we use them? Does anyone have any information or links on using an oscilloscope. Does anyone have a breif explaination on what it is used for? Should everyone use it? __________________ Best Regards, Mark T. Monciardini Riverlight Studios www.riverlightstudios.com DVX100/Final Cut Pro 4/Mac G5 Dual 1.8

July 9th, 2003, 10:23 AM	#3
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	Scopes plot the amplitudes of periodic electrical signals with respect to time, or with respect to each other in Lissajous patterns, or in a variety of other ways. So oscilloscopes permit for a visualization of something that you can't see--electrical voltage differences. With regards to video production, a video engineer will use a waveform monitor to look at the video signal being recorded to ensure that the levels fall within certain tolerances. One can "see" the electrical video equivalent of light exposure by looking at a waveform monitor. __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

July 9th, 2003, 11:31 AM	#4
Ken Tanaka Retired DV Info Net Almunus Join Date: Dec 2001 Location: Chicago, IL Posts: 6,943	Mark, I'm willing to bet a blank tape that you are actually thinking of waveform monitors and vector scopes rather than oscilloscopes. If so, these displays are used for color correction and are available in software form from within editors such as Final Cut Pro and Avids. See the book "Color Correction for Digital Video" for more detailed information. __________________ Lady X Films: A lady with a boring wardrobe...and a global mission. Hey, you don't have enough stuff! Buy with confidence from our sponsors. Hand-picked as the best in the business...Really! See some of my work one frame at a time: www.KenTanaka.com

July 9th, 2003, 03:56 PM	#5
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	waveform monitor = oscilloscope __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

July 9th, 2003, 09:20 PM	#6
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Well, as an ex-Tektronix salesman and repairman, I'll just mention that an standard oscilloscope isn't a waveform monitor. A waveform monitor is a specialized oscilloscope and is quite different in function from a waveform monitor or vectorscope. It takes special circuitry to decode the NTSC waveform and allow one to make a full spectrum of measurements. It even takes a special trigger circuit to get the normal oscilloscope to display a full-field or line trace properly. Do you need this measuring equpment? Depends on where your finished output will be shown. If it is destined for cable or broadcast, you almost certainly need to monitor the video as it leaves your editing system. I do use a portable Leader waveform monitor in the field when I really care about the proper setup of the camera system. I also have a Tektronix 520A in the studio so I can take a look at the video I deliver to the dupe rack. I find that the Canopus software waveform and vectorscope measurements are very accurate (they are digital, they should be. It's just some mathematics to generate the display.) But one has to have faith that the output will be no different than the digital data. I found, for example, on the old Canopus DVRexM1 composite video output, that it is only 75% of normal amplitude as measured on a waveform monitor using color bars. Canopus has admitted that that spigot does not perform correctly. Fortunately the S-Video and DV outputs are spot-on. Without checking the video, I would have difficulty getting television commercials accepted by the local Comcast tech center without having first set the levels by refering to the waveform monitor and vectorscope. And bumping the DV to BetaSP would be more difficult if the video were not to spec. DV will generate some very out-of-spec signals. Especially, as I've found, if one generates artwork in Photoshop or Illustrator. You cannot depend on the built-in NTSC filters in Photoshop or Illustrator or After Effects to keep you out of trouble. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

July 9th, 2003, 10:12 AM	#2
Vladimir Koifman Regular Crew Join Date: May 2003 Location: Israel Posts: 115	I believe Tektronix, the king of scopes, has some tutorials on its site.

July 10th, 2003, 12:13 AM	#7
Mark Monciardini Regular Crew Join Date: Jul 2003 Location: Salt Lake City, Utah Posts: 158	Thanks guys, this helps a lot. I will read that book! __________________ Best Regards, Mark T. Monciardini Riverlight Studios www.riverlightstudios.com DVX100/Final Cut Pro 4/Mac G5 Dual 1.8

July 10th, 2003, 12:17 AM	#8
Mark Monciardini Regular Crew Join Date: Jul 2003 Location: Salt Lake City, Utah Posts: 158	Mike, Can you tell me what Canopus software you are talking about? __________________ Best Regards, Mark T. Monciardini Riverlight Studios www.riverlightstudios.com DVX100/Final Cut Pro 4/Mac G5 Dual 1.8

July 10th, 2003, 11:30 AM	#9
Robert Knecht Schmidt Wrangler Join Date: Feb 2002 Location: Cleveland, Ohio Posts: 1,933	Mark, I think Mike's referring to the built-in software vectorscope and waveform monitor in the realtime Canopus editing aps, e.g., the latest Rex Edit, Storm Edit, EDIUS... Great post, Mike, BTW. Thanks. __________________ All the best, Robert K S Search DVinfo.net for quick answers \| The best in the business: DVinfo.net sponsors

July 15th, 2003, 01:18 AM	#10
Luke Gates Regular Crew Join Date: Feb 2003 Location: new jersey Posts: 151	you can use the oscilloscope (o-scope) to measure voltage levels (from DC to microwave), phase differences, signal presence (or absence) logic highs and lows, frequency response, distortion, and complex waveform analysis, to name a few. And as all you are arguing a basic o-scope is not going to enable you to view any video signal. You would need more specific equipment if you will.