Thanks Bob. I found the manual at canopus.com (after registering my 3-yr old ADVC-100). I also found some good explanations on caonpus' forum. Here's part of a 2003 post "0 IRE vs 7.5 IRE Setup - Some real world answers" by Tom Ogburn that helped me:
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"The quick answer is: If you are using US NTSC you should use 7.5 IRE setup for both capturing your analog source and playing off the timeline to an NTSC recorder or monitor. If you use Japan NTSC or PAL you should use 0 IRE.

"What is meant by 0 and 7.5 IRE? In video world, pure black is represented by 0 IRE and full luminance is represented by 100 IRE, so in theory, the blackest part of a scene should be at 0 IRE and the whitest and lightest part of the scene should be at 100 IRE. What complicates the issue is that early on in television, the original US NTSC standards called for the darkest part of the scene to be limited at 7.5 IRE units above 0, as early TVs could lose stability if they were called on to represent true 0 IRE black. This artificial black lower limit is also commonly refered to as "setup", as the black is "set up" to 7.5 IRE. US broadcasters adhere to this standard, and quite often will reject commercials or programs that do not contain the proper setup. Because of this, if your finished product will go to broadcast, this is something you must take into account. For other markets, and home video use, it is less critical, but still must be taken into account, especially if you are mixing and matching sources. Analog NTSC devices, like Beta and VHS machines use the 7.5 IRE output standard on their outputs, so if you are capturing from one of these sources, likely it will have 7.5 IRE setup. (there are exceptions, like analog outputs from a DV camera or DV deck.)"

DV, however, uses the full range of IRE, from 0 to 100. When you capture your video from a DV camera (or other device) via firewire to your computer, the full 0 to 100 range is there. As a quick aside, most professional DV, DVCPro, and DVCAM decks as well as some cameras allow you to add 7.5 IRE setup to their NTSC analog outputs, but the firewire output is still 0 to 100. Also, by adding the extra 7.5 IRE setup, the upper luminance is still limited to 100 IRE - it does not go to 107.5 IRE, so in effect your dynamic range has been decreased by adding setup. To my eye, adding setup will sometimes take some richness out of the video."
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I captured an NTSC VHS tape with IRE Setup +7.5 IRE, and it looks fine. In the video scopes I get levels from about -7% up to 109% (scope setting is Studio RBG on, IRE setup off). The -7% value only show up in some titles and graphics on the tape, but not in regular video footage. However, the white levels are up to 109% throughout the tape. Is this normal? Do I have to do something to the levels before burning a PAL DVD?

Douglas

Ah, yes.
Coming off a US VHS deck there will be 7.5% IRE!

Re your levels for DVD, Glenn Chan has an excellent tutorial on this.
You could use the Computer RGB to Studio RGB preset in the Color Corrector to get this back within legal however as thhe black only go below 0% during graphics you mich find your black getting a little greyish for most of the video. You can use the color curves to create a custom curve to get things precise, I do this while watching the scopes to make certain I've got it right.

Or you could just ignore the issue, unless large parts of the image are over 100% the clipping will not be very noticable, the data is not 'lost', it's just the players that clip it to avoid TVs getting upset.

Bob.

Tom Ogburn's 2003 post made it sound like it is physically impossible to exceed 100 IRE.

This is not the case at all.

100IRE is just an analog voltage level, and various NTSC and PAL-related standards specify when higher IRE levels can or should be used. PAL uses % instead, and has specs for up to 130% (with the percentages defined differently, too).

It's not really IRE (Institute of Radio Engineers) any more either, it's SUPPOSED to be "IEEE units", which of course nobody uses.

Thanks farss. The link to the tutorial he mentions is at
http://www.sundancemediagroup.com/articles/glennchan/levels_in_sony_vegas_part_one.htm

Douglas, I believe what you need to do in your case is to make sure the levels are being converted properly all the way throughout the chain. i.e. just make sure the equipment is doing conversions properly.

VHS/analog/NTSC --> digital/DV:
the analog black level will be at 7.5 IRE.
This will need to go to proper digital black level.
Setting the ADVC to 7.5 IRE should be right.

You can chek proper digital levels by using the waveform or histogram display in Vegas. The waveform will show things differently depending on the settings... if you follow the settings in my article, proper digital black level will be at 0 on the waveform.
The histogram will always have proper digital black level at 16... but if there are black bars on the side, this can make the histogram hard to read.

NTSC --> PAL (digital): I don't believe there's any way in Vegas which can mess with the video levels in this conversion.

PAL --> DVD: Vegas will handle the video levels correctly. Just make sure the video levels are good coming in.

2-

The Video Scope Setup setting is sort of confusing. Just keep in mind that the setting doesn't change your video levels at all. It merely changes where proper digital black level is displayed- at "0", or "7.5" on the waveform display. I prefer setting the scopes to "0", as there's no marking at 7.5. By setting the scopes to 0 / no "7.5 IRE setup", you would aim to put digital black level at 0 on the waveform.

I hope that helps.

Thanks Glenn, and Bob

I think I understand the levels pretty well now.

The next step is to render to MPEG. My project is setup as NTSC at the moment, with preview set to Simulate Device Aspect Ratio, which looks like the right aspec ratio. But when I change the project to PAL, she don't look so good no more. :-( Lousy interlacing artifacts. Is this what I should expect for this conversion? Does Vegas automatically convert from NTSC lower-field-first to PAL upper-field-first? Or do I have to manually change the setting in the project properties?

Do I need to do something in Event pan and crop (like match output aspect ratio) to get the NTSC to look right in a PAL project? Or should I just render to DVD Architect PAL video stream and forget it?

I'm also wondering if I should just render my NTSC footage to NTSC DVD and leave it to the DVD player to put the NTSC on my PAL TV? We play NTSC DVDs all the time on my Chinese DVD player, connected to our PAL TV. Are most DVD players format agnostic? Or am I just lucky?

Hi Douglas, I don't have much experience with PAL <--> NTSC conversions so I can't really help you out there.
Vegas 6 might handle the conversion a lot better than previous versions. (Better quality.)

2- A lot of PAL equipment will playback both NTSC and PAL signals. NTSC equipment usually just does NTSC. I'm not sure if that helps.

Try applying the Reduce Interlace Flicker switch to the events.
It may or may not help with your problem.

Certainly all of my gear plays NTSC and PAL, I'd say the same is true for at least 80% of all gear in PAL countries these days.


Bob.

Thanks. I will try burning both NTSC and PAL DVDs from my NTSC VHS tape. I assume that leaving the NTSC as NTSC will look better. I'll let you know.

But the one thing I'm wondering: do I have to CROP the NTSC event when converting to PAL, or just leave it as is?