Q about the blacker than black signal

Discussion in 'Archived Threads 2001-2004' started by George_W_K, Feb 27, 2003.

  1. George_W_K

    George_W_K Screenwriter

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    I was wondering about the blacker than black signal on DVD players. Is this signal only output through the component outputs, or can you take advantage of this using S-video too? I only have an S-video input on my television and it'll be awhile before I can upgrade to a new set.
     
  2. John Kotches

    John Kotches Cinematographer

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    Techniclly speaking blacker than black (really 0 IRE) is used for Progressive scan outputs. For interlaced output, 7.5IRE is the correct value.

    Since interlaced can go out via either component or composite or S-VIdeo, I had to answer a bit different from what you were probably expecting.

    Given your configuration, go with Blacker than Black off, and use S-Video, as it's the best choice you can currently utilize.

    Regards,
     
  3. George_W_K

    George_W_K Screenwriter

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    Thank you for clearing that up for me, John. I appreciate it.
     
  4. Don Munsil

    Don Munsil Stunt Coordinator

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    Much as it saddens me to contradict the estimable John Kotches [​IMG], in this he has made a common mistake.

    "Blacker than black" or "below black" is just picture information that dips below nominal black. This is important because some of the detail in the dark areas of the image on a DVD is typically encoded below black.

    There are a bunch of reasons for this, but mainly it comes down to the fact that CRTs don't maintain their black level perfectly, and when there is a bright image on the screen, the black level comes up a bit. The telecine operator moves the black information in the image down somewhat to compensate, and the shadow detail gets encoded below the normal black level. Some DVD players don't pass this information, but instead clip it at the nominal black level, which makes the shadow detail go away in certain films on certain scenes.

    What John is talking about is what some DVD manufacturers have been calling "enhanced" black, which is setting the black level to 0 IRE. John's advice is right on the money, IMO. If there's an "enhanced" black setting, leave it OFF, or set black level to "lighter" or "7.5 IRE".

    Blacker than black output is useful no matter what kind of connection you are using. There is only one DVD player I know of that lets you turn it off and on, which is the Toshiba 6200 (and some of the other members of its family). Sadly, on that player you should turn it off because it has a bug that makes the picture go crazy on certain discs if you leave it on. For essentially all other players, they either pass blacker than black, or they don't. And if they do, they will usually pass it over all of the different connections.

    Best,
    Don
     
  5. JohnnyG

    JohnnyG Screenwriter

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    At the risk of making a fool of myself [​IMG]...

    The NTSC system goes from 0IRE to 100IRE but NTSC black is 7.5IRE. If your display is set correctly, 7.5IRE IS black. You will not see (and should not see) any information below this level, regardless of whether it's encoded in the video or not.

    Non-NTSC black is 0IRE. Again, if your display is set correctly, you will not see anything below 0IRE (my Sencore pattern generator uses -4IRE for PLUGE but I don't know if this is the standard or not)

    As has been said, it's usually best to set it to 'lighter' if you're using s-video and 'darker' if you're using component video. Then, use a test pattern from Video Essentials, AVIA, Sound&Vision, THX Optimode, etc to properly set the brightness control (black level) on your display.
     
  6. George_W_K

    George_W_K Screenwriter

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    Thanks, guys. I didn't realize there was so much behind the statement "blacker than black". I just purchased a Denon DVD 1600 and it has an option for "Cinema". Is this the same thing as the aforementioned "enhanced" I should avoid? (I bought it online, so I don't have it yet.)
     
  7. StaceyS

    StaceyS Stunt Coordinator

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  8. Don Munsil

    Don Munsil Stunt Coordinator

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    John,

    You're absolutely right, in theory. In practice, the telecine operators are encoding real picture information below black, and that information is intended to be displayed. And what's more, it is displayed, even on a properly calibrated CRT TV. From what I can tell it works because on a CRT, even if you've got your display all calibrated to 7.5 IRE, in a bright scene the dark areas will come up slightly in brightness, exposing just a little extra of the signal below 7.5 IRE.

    My guess is that it's a natural result of the telecine operator working with a CRT monitor, but that's purely my supposition. It might also be that they're just trying to goose the overall scene contrast by clipping off a tiny bit of the blackest picture information. Or there may be some other explanation, but it's pretty clear that it only works correctly on a CRT.

    The take-away for me is that if you have a digital display, it's probably worth setting the brightness a tiny bit above perfectly calibrated, just to avoid clipping the stuff that's slightly below black. On a CRT, you can just calibrate normally, and the natural variance of the circuitry will do the rest.

    Don
     

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