Opinions on the need for below black pluge? (1 Viewer)

[Chris PC]

Do you have a dvd player that does NOT output below black pluge? If so, what does it mean to you in practical terms, calibration and picture quality wise? Anybody with an LCD projector and a dvd player that does not pass btb?

 

[ChrisWiggles]

I think I already sort of addressed this one!

But since folks here might be curious about this too, I'll repeat it,

It's not preferred if you can use a setting that doesn't clip BTB, or if you can get a better source, but you should still have a fine picture, especially with an LCD I wouldn't worry about it too much at all.

I should add in too that you'll want to make sure that you're only losing stuff below 16, because it's certainly possible that a source clips stuff above black or does other nasty things, and that you'd definitely want to avoid.

 

[Chris PC]

Thanx. I bought a Yamaha C750 and apparantly it does not pass black. I am using its interlaced outputs though, and the comments about not passing below black were regarding the progressive output, so it is possible that it passes below black on the interlaced output.

thanx again for the feedback,



P.S. I believe you, I am just looking for people's opinion on the severity of the problem if they are living with it themselves. For example, I am looking to see if I get responses like ... "My dvd player does not pass below black pluge, but I am still able to calibrate it fairly well and the picture looks good" or "My dvd player does not pass below black pluge and as a result, I cannot calibrate properly no matter what and the picture looks really bad".... or something in between.

Anybody have experience either way?

 

[ChrisWiggles]

You should be able to calibrate ok, and your image should also be ok. You can always test your system yourself by using the ramps on DVE, or Avia PRO. Consumer Avia does not have elements outside the 16-235 bounds.

 

[Chris PC]

Cool. I will check your guide (again). I have DVE (the navigation nightmare). Actually, I wonder if I could rip some of my DVE to an easier to navigate "backup" (fully legal, since I OWN it myself), without losing quality. Or just learn how to frickin' navigate it.

So to be clear, below black signal is only useful in calibrating? Below black does not do anything during playback itself? I understand it allows for precise adjustment of brigtness, but once you've done that, below black is no longer part of the action?

 

[ChrisWiggles]

No, not exactly, it can be seen and have an affect on the image sometimes. It's less important than peak whites, but black is kind of an elusive concept, so the actual black level floats around from 16.

Don Munsil posted a good explanation deep in my Guide thread at AVS, I post it here in its entirety:

 

[Chris PC]

Ok. So the way I would see a lousy picture is if there was substantial amounts of info on the dvd was below black, and it doesn't get seen, and is instead replaced with what? Does that mean I end up with crushed blacks or grey blacks? My guess would be if there are levels below black that should be passing but are not, my black detail is lost and I get crushed blacks. How bad it will be is another question. I really need to read up on this stuff some more

I will test the dvd player when I get it here. I am using the interlaced outputs with my iScan, so perhaps I will be lucky and the interlaced outputs will pass black (fingers crossed)

 

[ChrisWiggles]

Well, I think most content won't have much at all below 16 that would be visible, and if you have an LCD I probably wouldn't worry about it too much. I mean, if you had a completely idealized system, and broadcast quality CRT displays etc etc, it might be a slightly bigger deal, but I wouldn't get too worked up about it. I suggest you experiment with systems that do and do not crush BTB. I don't think you're going to see any difference at all unless you really try to hunt for it, and with an LCD display you might not see any difference at all anyway.

 

[Allan Jayne]

You can safely make your own choice if both your player and your TV handle "blacker than black".

If you set a blacker than black shade to be the darkest distinguishable shade, then official black will be dark gray. If you set official black to be the darkest distinguishable shade, then blacker than black and official black will look the same.

Whether gray shades slightly higher than official black get crushed is a separate independent topic. Coincidentally if you set blacker than black to be distinguishable from official black, black crush just above official black may be less of a problem.

The calibration will be different depending on the light level in the room.

The blacker than black spots in a PLUGE pattern make it easier to match official black with the darkest possible shade the TV can produce.

I do not agree that just because a DVD possesses blacker than black content, the artistic director of the movie intended that such content be distinguishable by the viewer. But the only way to find out for sure is to ask him, which is generally not practical.

Video hints:
http://members.aol.com/ajaynejr/blacker.htm

 

[ChrisWiggles]

I just wanted to be clear that I am not suggesting that anyone set values below black as "black" on their display. This is incorrect and elevates black level and you will have poor blacks that will incorrectly appear gray. Below-black content during alignment will not be distinguishable from black. However, strictly speaking as Don was alluding to in what I quoted, because "black" is an elusive concept (despite the seemingly specific definition that places it at digital 16), so on a BVM you may see some codes that are ostensibly below "black" because the actual code for black may shift around slightly.

 

[Allan Jayne]

>>> the actual code for black may shift around slightly

This is a problem with black level retention that some monitors or TV's may have. This problem is a separate independent topic.

The relevance is that, should the viewer not wish to have blacks crushed some of the time, it is necessary to elevate the actual code for black (I called it official black) high enough so as it drifts it bottoms out no lower than the darkest shade the monitor can display.

Calibration instructions probably don't have any specific procedure expressed in volts or foot lamberts for this. Instead the calibrator just raises the black level "a tad" if he wishes to allow for this.

 

[ChrisWiggles]

Not strictly, however. Keep in mind that the reference is CRT BVMs, and when mastering, even in professional displays, retention is not perfect, so there can be some drift on the monitor during mastering. This can lead to a slight reverse-float compensation in the actual code of "black," which is why it's simplistic to state that black is at 16, because it may or may not be exactly at 16, depending on the nature of the mastering of the content, and a lot of things. Reference black is defined at 16 for video, but the actuality of "black" may drift slightly. Digital displays generally do not have any drift at all, so if there is drift in the content because of CRT drift during mastering, the's a disconnect. Some displays such as Joe Kane's samsung projectors (DLPs) implement a slight approximation of that drift in black level to better mimic mastering monitors. Don and Stacey have more experience and understanding about this than I do, but that is the understanding in any case.

This is kind of what he was asking, which is, if data below 16 is clipped, am I losing anything important? Well, it depends, and it also depends on your system and your definition of "important."