DVD Black Level Confusion

Posted by Robin Luckey on September 30, 1998 at 13:40:51:

Can someone explain to me why DVD makers are advertising "expanded" black range, which pushes the black level to as low 0 IRE?

I understand that a standard color bar screen contains both 0 IRE and 7.5 IRE black, and that a player must be able to reproduce 0 IRE if you want to use a DVD like Video Essentials as a monitor calibration source. However, in the normally visible picture, 7.5 IRE is standardized as the darkest possible black, and your monitor should be calibrated for this. So why would I ever want my DVD player to output levels lower than 7.5 during normal playback?

Is this expanded black range merely a trick which "crushes" the video black normally at 7.5 IRE down to 0 IRE to "improve" the apparent quality or expand the contrast range? This seems to be an undesirable modification of the signal. Or is this just the manufacturer's way of stating that the device is capable of correctly outputing 0 IRE when required, and that some other DVD players are thus incapable of this?

Does the image storage encoding on DVD even accomodate the fact that there is a range of black possible below 7.5 IRE?

I am considering a purchase of a high-quality DVD player and I am wondering if there is anything I need to be worried about in all of this, and whether "expanded black range" should be a feature I care about.

Thanks,
Robin

Follow Ups:

• DVD Black Level Confusion kent h 23:59:34 10/01/98 (0)

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