To IRE or not to IRE

[Jim Giberti]

That is the question. I know this has been discussed here,and interestingly, after doing a search and following a couple of extensive threads, I found no conclusive sense of this question and that is: Do you calibrate your monitors to 0 IRE or 7.5 IRE when monitoring your DV footage.

I'd be curious to do a little poll here to see how the majority approaches it. I should ad the caveat of shooting DV, editing in FCP , outputting through a firewire deck to a NTSC studio monitor.

[Jeff Donald]

What is the final format for the project, DV tape, broadcast, DVD?

[Graeme Nattress]

First, digital video does not measure levels in IRE, which is strictly an analgoue measurement.

You don't calibrate your monitor to any particular IRE, but to the exact black level output of your DV deck that's feeding an analgoue image into your monitor. I don't know wether your deck outputs analogue NTSC black at 0 IRE or 7.5 IRE or someother IRE. Indeed, it matters not one bit. Play your bars in FCP, out through your deck and into your monitor. Now calibrate your monitor. It is now set up correctly for DV playback through FCP.

If you have any other devices connected to your monitor, you must calibrate the monitor for them similarly.

Graeme

[Jim Giberti]

<<First, digital video does not measure levels in IRE, which is strictly an analgoue measurement.>>

Of course Graeme, DV and FCP only speak 0-100

<<You don't calibrate your monitor to any particular IRE>>

Maybe I wasn't clear in my point...on many studio monitors, like my JVC, you select whether it is setup at 0 or 7.5 IRE...you have to choose one or the other 0 IRE being standard in Japan but American NTSC monitors are set up at 7.5 IRE.

<<but to the exact black level output of your DV deck that's feeding an analgoue image into your monitor.>>

Exactly, but when the monitor itself has a setup control, it creates the source of my querry/point.

<<Play your bars in FCP, out through your deck and into your monitor. Now calibrate your monitor. It is now set up correctly for DV playback through FCP.>>

Exactly as I always have, but obviously the image in very different if you set itto 7.5 IRE on the monitor, which is the set up of American NTSC, hence my question. My concern is obviously, what it looks like outside of my studio on the average person's NTSC monitor.

It's the same issue with reference monitors in my recording studio. IT doesn't matter what sounds right in an acoustically tuned environment over high end, flat speakers. What matters is that the final mix/edit sound/look as you intended when viewed/heard by the public.

I know this is obvious, but I also know it's been a source of confusion with a number of pretty bright producers and I always like to triple check, my beliefs.

So is your point: "choose either 0 or 7.5 on the studio monitor and it doesn't matter as long as you calibrate your black to the FCP bars?

[Jim Giberti]

<<What is the final format for the project, DV tape, broadcast, DVD?>>

Sometimes all of the above Jeff. Sometimes the same edit will go on to DVD that goes out to broadcast and vica versa. Sometimes I'll lay a project out to Beta SP for broadcast. These days I find most TV stations finally accept DV, where for years it had to be on Beta. If something is going out to lot's of stations, I send a DV master to a facility to make the 100 station dubs from a DV master and they make Beta SP transfers.

Of course there's always 60 secs of tone and bars at the top before the slate and countdown. Honestly, the issue of 0 vs 7.5...with NTSC showing black at 7.5, is the thing that I sometimes wonder if I'm overlooking something in my work flow.

I remember reading something where Charles was concerned that after working the same way he saw his edit on an external NTSC monitor and his blacks were crushed even though they were just right in his FCP to deck to his calibrated studio monitor.

I'm very confident in my calibration for the field and the studio..it's the dang IRE thing.

[Jack Smith]

I think Jeff was asking because if your project is to be broadcast NTSC it has to be 7.5 IRE to be "legal" so you would then set your monitor accordingly while viewing so that your adjustments to the video( contrast, brightness,gamma) would show accuratly
If the project is for web or projection or film setup would normally be 0 IRE for the same reason above
smitty

[Graeme Nattress]

Jim, It doesn't matter wether the monitor is set to 0 or 7.5 IRE - it should be totally irellevent. The IRE setup switch is a brightness control. It works in tandem with the brightness knob on the monitor, which should indeed be labeled black level. Pressing the IRE switch to 7.5 is just like taking the brightness knob and turning it sharply to left. Basically, on calibration, you want black to look black. It doesn't matter wether this is done through an external proc amp, the brightness knob, the IRE switch, or a combo of all three, as long as black look black. Now that said, you don't want to operate with all switches and knobs fighting each other!! If your DV deck's analogue outputs are 0 IRE, set your monitor to 0 IRE, and then use the brightness knob to dial in the correct calibration from bars in FCP played through the system. Similarly, if your deck is outputting 7.5IRE, set the monitor to that, and tweak your brightness knob until it looks spot on calibrated.

Jack, Remember, we're monitoring digital video here, and digital video can be thought of as living in a 0% to 100% range (or 16-235 in 8 bit levels). As long as you're giving your broadcaster a digital tape, IRE doesn't come into it as long as your monitor was calibrated to your system.

Graeme

[Jeff Donald]

Graeme is correct. This article from Adam Wilt's site should help explain how set-up effects NTSC DV. But black coming out of the camera should be 16. The danger comes when DV does not have set-up added and it is broadcast over NTSC system. The blacks will be too dark (if they aren't adjusted by the station). If set-up is added to DV tapes and the station also adds set-up, the images will appear washed out. If you provide a DV tape to a duplication house, they should be adding set-up to the output if the tapes are going to analog.

So, to answer you question, DV, by the very definition of the DV standard, should not have set-up. The monitor should be calibrated accurately for the DV standard. If you are going to Beta SP (NTSC), the deck outputting the DV signal should add set-up and the monitor connected to the Beta deck should be calibrated to NTSC.

[Graeme Nattress]

Just to add, that all digital video formats are identical in this regard and that they do not have setup. It is wrong to apply setup to digial video tapes, wether they be DV, DigiBeta, DVCPro50 or HDCAM! As everyone's monitoring system is unique, it is important that you calibrate your monitor to your system.

The ony correct place in any system to add setup is on conversion of digital video to analogue video. The only correct place to remove it is on conversion of analogue to digital.

Also, just for anyone else reading this thread, setup, or 7.5IRE only applies to north American NTSC analogue video. Everywhere else in the world has analogue black at 0IRE.

I recently received a DV tape that had been dubbed from BetaSP to DV. On capturing the DV tape via firewire I found that the blacks were at 7.5% in FCP, rather than the digitally correct 0%. This is because the dub house got it wrong! They should have known, that on conversion from an NTSC analogue format to a digital format, that 7.5IRE setup needs to be removed, so that black is at digital 16, which is 0% in FCP.

Graeme

[Norm Couture]

Jim,
I have a Sony consumer DV camcorder. Its analog A/V output is 0IRE. That's correct for playback on any standard NTSC TV set in Japan and anywhere else except North America.
For correct viewing directly from the cam's A/V out to a North-american NTSC monitor or TV set, the black level should be raised somehow to 7.5IRE.
In the digital world like the computer monitors, Firewire outputs and NLEs, the black level stays at 0IRE.
On the other hand, all North-American NTSC DVD players automatically add the 7.5 pedestal to their analog outputs.
So I transfer my footage via Firewire, edit it and burn it to a DVD without bothering about the black level setup. When I play the DVD on my living-room player, I get the correct black level for the TV set.

[Mike Rehmus]

Fortunately, some NLEs have a setup level selection for analog output. So, if you are in the US, you set it to 7.5 and know that you will deliver OK tapes and that your analog output and viewing systems can remain true to the NTSC standard.

Internally the NLEs use 0 IRE as the full-black level regardless of what one has set for the analog output.

[Jeff Donald]

If your making your own dubs or DVD's and you understand your equipment and the set-up requirements for NTSC you won't have any issues. If you send tapes out for dubs etc. then you have to be sure the duplicator understands your requirements for set-up and your intended usage of dubs.

[Jim Giberti]

Thanks for the great discussion guys. For the record, I keep everything at 0 IRE and as Graeme has clarified, I've always assumed that calibrating to either ) or 7.5 would result in the same monitor image as long as I was calibrating to the blacks coming out of my FCP bars.

My biggest concern has been the difference between analog deck conversion and DVD conversion. Assuming that all DVD players adjust for 7.5 then no problem. And I giuess I'll continue to trust the production depts at the stations to ad setup from digital masters..

My remaining concern is that I haven't been able to ascertain whether the DV deck I use (AG-dv1000) outputs 0 or 7.5 from it's Y/C analog out, which would of course determine how I handle dubbing directly from dv to my UVW 1800 beta deck.

[Jeff Donald]

Do you have a waveform monitor? If not, maybe the place that makes your copies can check a beta tape for you. A call to Panasonic might resolve the issue also.

[Mike Rehmus]

<<<-- Originally posted by Jim Giberti :
My remaining concern is that I haven't been able to ascertain whether the DV deck I use (AG-dv1000) outputs 0 or 7.5 from it's Y/C analog out, which would of course determine how I handle dubbing directly from dv to my UVW 1800 beta deck. -->>>

Play the analog output back into your editing system (I'm assuming you don't have a waveform monitor) assuming (again) that you have analog inputs for your NLE. Then use the built-in Waveform Monitor software to evaluage the footage.

Or put out some 7.5 and 0 IRE footage and look at them on the same monitor. You can get there.