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7.5 ire vs 0 ire DV Tape
Hi guys,
I received a DVCAM tape of a show we did for archival purpose. It was made from the DVCPRO50 Master through the SDI output. The thing is the MASTER is at 0 ire (on digital scope) and so is the DVCAM copy. I was trying to capture the DVCAM tape the edit a promo teaser but the image was very dark when captured in FCP. Is there a way to capture through firewire and puch up the luminance of the image? Or should they have provided a DVCAM tape at 7.5 ire?I use FCP5 and a Sony M10U HDV/DVCAM/DV deck
Thanks
Mat
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11 Replies
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Digital Black is 0. Analog black is 7.5. Since you are working inthe digital realm, your IRE should be 0.
How are you judging the quality of your image? Computer monitor or NTSC monitor?
Shane
Alokut Productions
http://www.lfhd.net -
I’m assuming you want a version for American NTSC?
If so, then black is 7.5 IRE.
Since both the master and copy are at zero IRE there’s not a lot you can do about it — or need to — if it’s just for archive.
However, if you want to distribute it to U.S. markets, then you’ll have to fix it so that the black level is at 7.5 IRE. You can do this by dropping a 3-way color corrector filter onto the entire program and doing a global correction. Hopefully there’s bars and tones at the head of the show.
Be sure to view your signal with a broadcast monitor that’s been properly set up. Don’t rely on your computer monitor as the results can be dramatically different.
And I strongly recommend checking the signal values through a waveform monitor enroute to the video deck (assuming you’re distributing via Betacam SP or similar). The FCP waveform monitor and vectorscope might be OK but what you really want to see is what’s going to tape if you’re outputting via analog. Your output device may or may not translate the video data exactly as FCP might assume.
Dean Sensui — http://www.HawaiiGoesFishing.com
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7.5 is only for analog. A DVCAM deck should only read 0 IRE for proper black level when viewed on a digital scope.
You have the option on many DV decks to add 7.5 setup on the ANALOG output only. This is usually done via a menu setting, though not all decks have this. If you need to output to an analog tape (a Beta SP dub, for example) and your deck does not have this setting, then you would need an external TBC to adjust your black level. Again, this is only necessary in the analog realm. -
Ah, but it should be at 0% in FCP. That’s correct.
Read this article I wrote for more info:
https://www.kenstone.net/fcp_homepage/video_levels_nattress.html
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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I disagree Dean. No adjustment is necessary.
The digital realm is 0 and analog is 7.5. When you edit in FCP the levels will be at 0. That’s standard in all NLEs.
ALL digital tapes record at 0 IRE as well. The 7.5 setup is added by the DECK during PLAYBACK.
When you are laying off to Beta or other analog, the CONVERTER BOX will add the necessary setup. If you add setup in your NLE, when you lay it off, the box will add another 7.5 and your master will be washed out.
Now, if you are monitoring through the digital deck and the output looks dark on a properly calibrated monitor, then you need to add PLAYBACK setup through the menu option on the deck (if it has that option).
pxlmvr
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Agreed. However, if you’re using a DSR20 or similar deck, you’re faced with the problem many of us are. We can’t bump up the analog output setup. It’s not an option. And if you don’t have an external TBC then adding a proc amp 7.5 ire effect to the entire timeline is a great poor man’s trick for making a vhs dub out of the DSR20. It has the same result as running it through an external tbc. It’ll also do the trick if you have to make a dub to a rented beta deck out via the svideo port.
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John…
I’m working with a Blackmagic Decklink card with component out (analog) to my Betacam SP deck. All measurements are taken from the deck with an MM400 waveform/vectorscope, not in FCP. In fact, I’ve never used FCP’s built-in scopes.
With standard SMPTE color bars there’s three dark bars at the lower right corner, and one of them is supposed to go to zero, one goes to 7.5 and one goes to 10.
If I set up my Decklink to output black at 7.5 IRE, that “zero IRE pluge” gets clipped at 7.5 IRE. Decklink creates a 7.5 IRE “floor” below which nothing can go, and that’s not correct when it comes to laying down reference color bars at the head of a tape.
Therefore the Decklink card is set up to allow values to go all the way to zero to ensure accurate translation of SMPTE bars to tape.
With that in mind, it then becomes possible to create programming with illegal black levels, at least as far as U.S. NTSC is concerned.
So that means the program material has to be monitored and, if necessary, corrected in post to conform black levels to the 7.5 IRE standard. The same goes for 100 IRE white. The Decklink card allows values beyond 100 and that has to be monitored in post to ensure all levels are legal and consistent.
The results I’m getting for our show has come out just fine in the cablecast. Occasional air checks show that the levels are also being translated to within a few IRE points through Time/Warner’s cable network. It’s definitely not washed out.
Again, I’m monitoring all levels at the deck. Not in FCP. What matters to me is what ends up on tape since that’s what gets handed over to the broadcaster.
Dean Sensui — http://www.HawaiiGoesFishing.com
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Adding an effect to the timeline to boost the blacks will a) reduce piture quality, and b) take a lot of time to render. You don’t have to do it often before it becomes more cost effective to get either a proc amp, or to just farm it out to someone else – or even a Decklink or Kona card which will play out the DV timeline direct to Y’PbPr with the correct analogue voltages for you.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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I have a different kind of problem with 7.5 ire. I am now starting to upload some of my clients spots to DG systems in Burbank. In other words, the spots don’t touch a tape. They are all digital files ftp’d to DG. I use Joe’s broadcast filter and it seems to work alright. Is there any other way to do this, or is the Joe’s filter the best case scenario?
Thanks
Chip
Chip Whiting
99 Productions LLC
541-343-0099 -
Black should always be at 0% in FCP no matter what.
Graeme
– http://www.nattress.com – Film Effects and Standards Conversion for FCP
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