DVD black level control: on or off - AVS Forum
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post #1 of 26 Old 10-30-2002, 03:49 AM - Thread Starter
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I posted a similar question elsewhere, but due to my poor subject title, I am reposting under a more general subject title in the hopes of getting more responses. (Thanks to bcwang and pnichols who have already responded...)

Anyway, when calibrating and viewing DVDs using a progressive scan player hooked up to a HD-ready direct-view CRT TV via component cables, should I turn the enhanced black level control on the DVD player on or off?

I ask this because I have the Sound & Vision Home Theater Tune-Up disc (which is co-produced by the same people who did the highly regarded Avia disc), and it very specifically says to turn the enhanced black level control on the DVD player to the off position before calibrating. This contradicts my DVD player's manual which says to turn on the enhanced black level control when using component video outputs.

For the record, my TV is a Sony 36XBR450 and the DVD player is a Panasonic RP82.

(Moderators, please feel free to merge the two threads under this subject title...)
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post #2 of 26 Old 10-30-2002, 06:53 AM
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I believe most of those 'black enhancing' controls actually lighten dark scenes. Black de-enhancing if you ask me. I'd say you'd want them off.
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post #3 of 26 Old 10-30-2002, 10:35 AM - Thread Starter
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Okay, here are two online references. Both "seem" to say that you should turn the black level control to off, at least that's how I interpret them:

The Setup: DVD Players

Video Insights: Black Level Calibration

The Ultimate DVD Boot Camp

I guess I'll turn off the black level control, as the S&V disc tells me to do...
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post #4 of 26 Old 10-30-2002, 11:11 AM
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So reading around, this is what I've gathered and what I think is correct.

DVD's are recorded from 0 ire - 100 ire.

DVD players should be set to use 0 ire black and the monitor should be setup based on this to get the best picture out of dvds. Otherwise by watching at 7.5 ire the dynamic range of the dvd picture is compressed

But at the setting optimal for dvd's, regular ntsc broadcasts and outputs from the vcr and laserdisc will look too bright because they use a 7.5 ire for black.

HDTV broadcasts I read use 0 ire for black as well, which I figure is correct since on my set, after calibrating my display for 0 ire from my dvd player, the hdtv look's perfect, but if I were to calibrate using 7.5 ire, the hdtv shows would be too dark and the dark scenes unwatchable.

So I think the best thing to do is if your tv has multiple calibration settings, set one using 0 ire (enhanced) through the component video for best dvd watching and hd program use. And set another through s-video or composite using 7.5 ire (standard) for all other daily broadcast, vcr, etc.. usage.

If you read those 3 links above, you will notice they say to setup the tv using the standard setting, but only because it will make all the other sources look correct, and not be a hassle when going from dvd to regular tv. They did not say it was to get the best picture out of dvd.
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post #5 of 26 Old 10-30-2002, 01:46 PM
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bcwang,

As far as I know, you have it exactly right. ;)

What you describe is how I have my HT equipment set up and calibrated - 0 IRE ("Darker") for DVD progressive and HDTV and 7.5 IRE ("Lighter") for regular TV and VCR.

Thanks for your excellent, crystal clear explanation!

Phil
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post #6 of 26 Old 10-30-2002, 02:52 PM
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There really should be no video quality difference between 0 IRE and 7.5 IRE black level on a DVD player, assuming the DAC was designed properly. Once you calibrate the TV for each, they should look exactly the same.

As these online references mention, setting it to 7.5 IRE allows you to keep the TV calibration the same as you move from DVD to VHS to broadcast. 0 IRE allows you to match HDTV. If you have all of those sources coming in, you'll need two memories on the TV anyway. If you don't have HDTV coming in, putting your DVD player at 7.5 potentially reduces the hassle of switching video memories all the time. Some TVs will allow you to specify different settings for different inputs, so if you have one of those and your DVD is the only thing coming into the component input, you could set it to 0 or 7.5, but again it won't make a bit of difference to the video quality.

An additional issue to keep in mind is that a few DVD players pass the blacker-than-black signal (used in PLUGE patterns on some calibration discs) only if the black level is set to "normal" or 7.5 IRE. So if you want to use a PLUGE pattern (which is not used on Avia or Sound and Vision), you need to check that first. And of course some DVD players don't pass blacker-than-black at all no matter what the circumstances.

Bottom line: in general, I say leave it at 7.5 for the convenience factor. I happen to have a player that doesn't have an option and is always at 0, and quite frankly the inconvenience is annoying. I don't like having separate memories for DVD and satellite.

As to the S&V disc, I don't know why the instructions on the disc say to turn on "enhanced" black, but I can ask Guy and find out.

Don
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post #7 of 26 Old 10-30-2002, 03:19 PM
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Guy's on vacation, but Stacey theorized that the folks who put together the S&V test disc don't much care for the 7.5 IRE setup. I personally agree, but we're sorta stuck with it.

There is a really outside risk that if the setup is applied in the digital domain in the DAC, you could get roundoff issues and/or quantization noise. I just don't personally believe that a DAC manufacturer would be likely to make that mistake. The appropriate place to set the black level would be either on the analog side of the DAC, when the bias voltage is applied, or in some intermediate oversampled stage when the roundoff errors would be minute and lost in the noise.

Stacey wanted me to be sure to add that there's no excuse for TVs, especially HDTVs, not to have multiple memories, given that HDTV not only has a different black level standard than NTSC, but also a different color decoder matrix as well. Also, the standard for 480p is 0 IRE black level, so the TV should anticipate that and automatically adjust for it.

However, given that lots of TVs don't in fact have all this flexibility, I return to my original assertion that given a choice you should use the one that causes the least hassle.

Don
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post #8 of 26 Old 10-30-2002, 03:56 PM
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While Ovation did work on S&V, it was S&V who wrote the script and made all the decisions. That is why you can't press menu on the FBI warning with S&V but you can with Avia.

Along with what Don said, there are DVD players today that don't output correctly when set to enhanced black. Not sure what they are doing, but it does not appear correct.

I have two DVD players. Both using same deinterlacing engine and same video encoder. When both are set to 0 IRE, one clips everything below and the other does not. At first you might suspect the MPEG decoder, but I also have SDI out on both players and they produce the same signal when you go this route. So I supsect some video encoder setting.
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post #9 of 26 Old 10-30-2002, 04:13 PM
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sspear, how would you go about checking to see if a dvd player clips anything below a certain level? Is there a test pattern on avia or ve that you can use to see this?
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post #10 of 26 Old 10-31-2002, 08:36 AM - Thread Starter
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Thanks for all the replies. Since my TV doesn't have memory for the different inputs, I will set my DVD player's black level to the off position. I really don't see much difference in either setting anyway. As Don says, once the DVD player has been calibrated for both settings, they should look the same...
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post #11 of 26 Old 11-01-2002, 09:39 PM
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Quote:
Originally posted by mrwilson
I believe most of those 'black enhancing' controls actually lighten dark scenes. Black de-enhancing if you ask me. I'd say you'd want them off.
I think "enhanced black" mode sets the player to 0-IRE black level, whereas normal mode is 7.5-IRE black.
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post #12 of 26 Old 11-01-2002, 09:42 PM
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Quote:
Guy's on vacation, but Stacey theorized that the folks who put together the S&V test disc don't much care for the 7.5 IRE setup. I personally agree, but we're sorta stuck with it.
I believe that if they are telling to turn "enhanced black" off they are telling you to set up for 7.5-IRE black. That would be normal mode. "Enhanced," to me, implies 0 IRE.
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post #13 of 26 Old 11-02-2002, 10:55 AM
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enhanced/below black/blacker than black = 0 IRE, normal = 7.5 IRE

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post #14 of 26 Old 11-02-2002, 11:03 AM
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I read somewhere in a manual that the enhanced black level should be turned on during video calibration and off during normal playback use. The enhanced black level is meant only for setup purposes and not to "enhance" anything during playback.
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post #15 of 26 Old 11-02-2002, 12:17 PM
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I've read that in a manual too, but I think it wasn't to turn off enhanced black, it's to turn off blacker than black for normal viewing. I think what they meant is to turn on blacker than black when calibrating with a pluge pattern because it needs to show the blacker than black information, and turn it off during normal material because normal material isn't supposed to have anything blacker than black. But I think I read somewhere a dvd test which showed a number of scenes with information blacker than black. So maybe it's best just to leave it on.
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post #16 of 26 Old 11-02-2002, 02:27 PM
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Here's an explanation of 0 IRE and 7.5 IRE, why we have them and where you should set the level in your application. Cliff notes: if you have a TV or monitor that will remember different settings on each input, use 0 IRE from the DVD player. If TV broadcast signals and video input signals have only one setting for all (ie; they're each the same), 7.5 IRE is more appropriate.

From VE:

>>>In the original black and white television system the voltage level for picture material at black was zero Volts DC or 0 IRE. (IRE and other terms used in this explanation are defined in the glossary of terms.) The level for white was 716 millivolts or 100 IRE. When color first came to NTSC it became necessary to raise the level of black to +7.5 IRE, compressing the dynamic range between black and white. By the time all three networks had gone to color in 1964 the +7.5 IRE black level was no longer necessary, but the rule wasn't changed. In 1990 there was a push in the program production industry to change it back to 0 IRE. That change actually took place in Japan but didn't happen here in the United States. Part of the push for the change came from the fact that a lot of program material was being produced in the SMPTE component video domain which uses 0 Volts for black. The majority of DVD's are mastered using 0 Volts DC for black. In reality all DVD's should be mastered using 0 Volts DC for black, but there are exceptions. The dynamic range of the component video picture is enhanced relative to the standard composite NTSC color system. The DVD player will reduce that dynamic range, moving it from 0 IRE to
+ 7.5 IRE, in providing an NTSC output which is necessary for compatibility with standard home display devices. Which position should you use? That depends on the display device itself or the video processor driving the display and/or how the DVD player is being used in the entire home entertainment system. Ideally you would want to use the 0 Volts black position to preserve the dynamic range available from the disc itself. That is only practical if the set has an individual memory for the enhanced mode. This individual memory should be able to remember settings for contrast and gray scale in addition to brightness. We've come across video processors claiming compatibility with black at 0 Volts DC but found that some of them don't actually have that capability. In short, reading manufacturer's specifications doesn't always give you an accurate picture. If the processor reports an ability to deal with black at 0 Volts and has at least 10 bit processing, chances are far better that it will function properly than if the processing is 8 bits. Video processing in many Plasma displays is less than 8 bits. As a result you'll see lots of problems in the picture, especially in the areas near black. The selection you make will most likely affect all video outputs of the DVD player. If you are routing the NTSC output for signal monitoring and the component output for actual viewing, the NTSC picture probably won't look correct. Blacks will be crushed from the DVD picture if the NTSC monitor has been set up to look correct on all other sources. It takes a well thought out system to take advantage of the 0 volt "Enhanced" capability of DVD players.<<<

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post #17 of 26 Old 11-02-2002, 04:28 PM
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Some Toshiba DVD players let you turn Blacker-than-block on/off. It is this that you turn on for calibration and off for use. This is different from the enhanced black option.

bottom line there is a nasty bug in the Toshiba players if you leave BTB on during a film. You will get this ripple effect that is wild. It seems to happen mainly on WB titles.

As far as enhanced black. Set it and then calibrate. If you change it, re-calibrate.
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post #18 of 26 Old 11-02-2002, 05:08 PM
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Stacey, can you elaborate on what to look for in this situation? This is the first time I've read about this:

>>>bottom line there is a nasty bug in the Toshiba players if you leave BTB on during a film. You will get this ripple effect that is wild. It seems to happen mainly on WB titles.<<<


I checked Toshiba's site to see if they had any info on what setting to use. I interpreted their info as "leave it on all the time":

>>>Video Black Level Expansion and PLUGE
Grayscale in video is measured and tracked on a scale of 0 (black) to 100 (white) IRE units. In NTSC video we have traditionally assigned the 7.5 IRE value as being the black cutoff in a picture. The EXPANDED mode in the "Video Black Level Setting" menu enables Toshiba DVD players to output a 0 IRE signal for richer, deeper black tones in every image.<<<

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post #19 of 26 Old 11-02-2002, 06:28 PM
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Joe

The ripple is an old issue and was covered a year or two ago. It is because of this reason that Arcam does not allow you to turn BTB on. While Arcam is built from the ground up, it uses the same MPEG decoder as Toshiba, a Zoran Vaddis.

The RP6200 and 9200 both have this issue. Do you have a copy of Lethal Weapon 1 directors cut? If so, go to the scene were Mel Gibson is just getting on top of the roof where the jumper is. As he comes up the ladder, you will see it. It is not hard to spot. :) This will only happen with BTB on. If you turn BTB off, you are good to go. It happens in many more places, but that is the best example.
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post #20 of 26 Old 11-02-2002, 07:36 PM
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"Blacker than black" and "enhanced" black are two completely different things. Blacker than black refers to signals that are encoded lower than nominal black on the disc. For example, a PLUGE pattern has a blacker than black bar to help you find the proper mapping between disc black level and monitor black level. This bar *should* be reproduced by the player no matter what the "enhanced black" setting is. Unfortunately, in some cases players won't reproduce blacker than black signals if the "enhanced" black switch is turned on (which makes no sense at all), and some players won't reproduce blacker than black no matter what (which makes even less sense).

As Stacey has pointed out, many films actually have blacker than black information encoded in the dark areas of the image. If those blacker than black areas are clipped too hard, the result can be artificial-looking, where the black areas look strange and not smooth, especially on a CRT monitor.

"Enhanced" black is just a switch that changes the nominal black level output by the player from 7.5 IRE to 0 IRE. Some players have the control labelled "0 IRE" and "7.5 IRE," and some players have it labelled "darker" and "lighter". Whatever the labels are, it's easy to figure out which is 7.5 IRE and which is 0. Whichever one produces the brighter image when you switch between them is 7.5 IRE.

As mentioned more than once in this thread, you can choose 0 IRE or 7.5 IRE nominal black level, and it really shouldn't make any difference to the picture as long as you calibrate the monitor and then leave the switch alone from then on. I disagree with VE on the "dynamic range" argument. Yes, going from 0 to 7.5 IRE compresses the dynamic range, which would be an issue on analog recording and RF transmission equipment, but it's a complete non-issue for DVD. When you are in 7.5 IRE mode, it just changes the bias voltages applied at the end of the D/A process. The bits stay the same all the way up to and into the DAC. And the cables that move the image from the DVD player to the TV have so much bandwidth that the "dynamic range compression" is immaterial.

If you have blacker than black data on the disc, and "enhanced" black is turned ON, the blacker than black areas will dip below 0 IRE, down to maybe -2 or -3 IRE at most. If you have "enhanced" black turned OFF, the blacker than black areas will dip below 7.5 IRE, down to 5.5 IRE perhaps, but not all the way down to 0.

So if the S&V disc says to turn "blacker than black" ON, that makes perfect sense. Most DVD players don't even have this control, but certainly if yours does you should turn it on when you're calibrating. And then when you're done calibrating, you should leave it on, unless it's a Toshiba 6200 or 9200. In that case, you should get a new player. Just kidding. :)

But "enhanced" black or "darker" or "0 IRE" or whatever you want to call it is pretty much a non-issue except to make the DVD player closer to your other equipment.

Hmmm... there is one issue that could make a difference. If the signal is going to go through another analog to digital conversion after leaving the DVD player, then you *could* potentially get slightly better results with the player set for 0 IRE. For example if you have a digital display (plasma, LCD, DLP, etc.), or if you are outputting an interlaced signal into a deinterlacer (iScan, Omega One, Faroudja), or outputting an interlaced signal into a TV with an internal deinterlacer (pretty much all modern HDTVs), then the expanded range you get with 0 IRE might make a tiny difference. Whether it's a visible difference is debatable.

The thing is, any time the signal has to be redigitized, the A/D converter has to be calibrated to a particular range of voltages. It's going to map that range internally into (most likely) an 8-bit value. And probably the range of voltages the designers will choose will be from slightly under 0 IRE to slightly over 100 IRE. Any voltage under or over that range will be clipped and information will be lost.

So if your DVD player is only outputting 7.5 IRE (5.5 IRE with blacker than black) to 100 IRE, then some of the lower end of the possible range will be wasted. And since the signal is going to be quantized to an 8-bit number, that could make a difference. On the other hand, if you set the player to 0 IRE, and it in fact is outputting -3 IRE, the digitizer next in the chain might just clip off all the lowest blacks.

And on the high range, some DVD players have their white level set at 108 or higher, and then they go higher than that when there are peaks on the disc. Stacey has seen discs where the whitest parts of the image are 120 IRE, on a good player. On a player that already has a white level that is nominally at 108, the end result would be a lot higher than any digitizing system would be designed to handle.

I've seen this personally on my Sony VW10HT LCD player. Feed it a signal that is too low or too high, and the lowest and highest parts get clipped. Similarly, I have an iScan Pro, and it will clip anything that is a little below 0 and anything much higher than about 115-120.

The answer to all of this is to carefully check (with test patterns) to make sure none of the image (including blacker than black) is being clipped, and if necessary use the image controls on the player (if any) to adjust the black level and/or white level to avoid clipping.

If you have a progressive player going straight into a CRT television, whether direct-view or projector, it's highly unlikely that any extra digitizing is going on. The signal path is typically analog from the back of the DVD player all the way to the electron guns.

In the end, I very much doubt that even with the D/A conversion the quantization difference between 7.5 IRE and 0 IRE black level is visible. The clipping issue, though, can be very visible. If you have a digital display or a deinterlacer in the signal path, it's important to check for clipping and do something to eliminate it if it's there.

Don
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post #21 of 26 Old 11-03-2002, 03:37 PM
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When you say there is a problem with the "Toshibas", do you mean all Toshibas or just the two specific models (RP6200 and 9200) mentioned?

I have an SD2109 in the living room system. According to the explanation in the manual, enhanced = expanded = 0 IRE. The player is to cut off black below 7.5 IRE when the "normal" mode is selected.

Here's my evaluation of the two settings -- enhanced vs normal. In the enhanced mode, blacks are blacker/darker. Colors are richer and seem to be full bodied. There appears to be greater contrast in the picture (ie; the intensity -- Y -- range of the picture, from lightest to darkest, has been increased). In the normal mode, blacks begin to have a slight shift towards "dark gray". The PLUGE pattern is passed to the TV in either mode.

The only analogy that I can make is a comparison to photography. It's the difference between slide film (colors are richer and more vibrant, the picture seems closer to "real") and print film (developed by a cheap photolab). The colors will look washed out and pale, the print will appear subdued and will have this "veiled" quality about it.

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post #22 of 26 Old 11-03-2002, 04:05 PM
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Joe,

The differences you're seeing are because you're changing the black level without recalibrating the TV. Changing from 0 to 7.5 does not "cut off" the bottom end, it just shifts it upward. (FWIW, It's supposed to leave the nominal white level at 100 IRE, but there are multiple examples of players where the range is 0-100 IRE in "enhanced" mode and 7.5-107.5 in "normal" mode.)

Believe me, if you recalibrate the black level & white level (brightness and contrast), and possibly color and hue, the 0 IRE mode will look exactly the same as the 7.5 IRE mode (assuming you have two different memories on your TV so you can switch calibrations when you switch modes). You shouldn't have to adjust hue or color when switching between two different black levels, but you never can tell what mischief will happen between the DAC in the player and the controls on the TV. It is possible for changes in the brightness control, for example, to affect the color on the TV.
Not likely, but possible.

On a related note, there's another misstatement in the V.E. explanation of black level that I want to point out - it says that DVD is always encoded with black at 0 IRE. This is completely false. DVD does not use IRE at all. It uses the digital video standard, where black is at 16 and white is at 235 on a scale of 1 to 254. 0 and 255 are used as signaling values. IRE simply does not enter into it at all.

So on a player set for 0 IRE black level, 16 on the disc is mapped to 0 IRE, and 235 is mapped to 100 IRE. Everything else in between is spread out between those values linearly.

If the player is switched to 7.5 IRE black level, then 16 on the disc is mapped to 7.5 IRE, and 235 is mapped to 100 IRE, and again everything else is spread out in between.

You can see as a consequence of the above that if you have a TV calibrated to 0 IRE and switch the player to 7.5 IRE black level without recalibrating the TV, that everything on screen goes up in absolute brightness. Every color has white added to it, which makes everything look paler. Blacks become gray, and the overall contrast level drops to a maximum of 100/7.5, which is 13.3:1. You can understand why everything looks washed out with a contrast ratio like that.

Similarly, if you take a TV calibrated to 7.5 IRE black level and change the DVD player to 0 IRE, then every color on screen will get darker, and have white subtracted from it, which will make everything look more saturated (in fact the colors will be more saturated). Unfortunately, the lowest color values will all be clipped off (by the TV, not the DVD player), and while all the saturated colors may look nice, they're not the intended colors.

This difference between 0 IRE standard for progressive and 7.5 IRE for interlaced is the primary reason that we see a seemingly endless parade of folks saying "Wow, I got a progressive DVD player and the colors got so much richer." They might as well have said "I turned down the brightness on my TV and the colors got so much richer" because it's the same thing. They also get a rude awakening when they try watching a dark movie and can't see anything that's going on in the dark scenes.

Progressive DVD and 0 IRE black level is not supposed to make the colors richer. It's not supposed to do anything to the colors, so if you see a difference, that just means the calibration is off.

Honestly, I think the fact that you need to calibrate monitors and the fact that there is this difference between 0 IRE and 7.5 IRE is a testament to how screwed up the consumer electronics industry is. People should not have to know this stuff. People should not have to buy calibration equipment to get a decent picture. You should be able to expect to buy a DVD player, get it home, hook it up to a normal TV and get a good picture with the right settings the first try. If the CE industry put their heads together, they could solve this and eliminate the need for calibration at all. But it's not considered a priority. And for most people, their brightness and contrast are cranked up so high that when they switch to 0 IRE black level, the image is closer to calibrated than it was at 7.5 IRE. Now *that's* a crying shame.

Don
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post #23 of 26 Old 11-03-2002, 04:19 PM
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I believe the last paragraph in your reply is probably the greatest downfall of the consumer video world. There is only one correct setting/calibration and there should be no adjustments necessary. Of course, there is the little problem of light falloff, parts wear, etc. :-)

Unfortunately, the living room TV has only one setting for all, so I can't swap back and forth. I'll give comparisons a shot when I can. The den system is... well... it's a long story... won't get into it here... neighbors, you know...

The most efficient path is seldom a straight line.
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post #24 of 26 Old 11-03-2002, 08:54 PM
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So if the S&V disc says to turn "blacker than black" ON, that makes perfect sense.
The disc says to turn enhanced black off. I expect the reason is to prevent people from winding up with sets that are adjusted probably for the DVD player but not for regular TV watching.
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post #25 of 26 Old 12-01-2002, 07:22 PM
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Quick question for you all. I'm currently feeding my Barco 1208 with a quadscan pro connected to an interlaced signal from a Panny RP 82. I previously had it isf'd on a Sony DVP 7000. Following the manual I set the Panny to the blacker setting but like many others have noted my picture was just too darn dark. When I tried Avia's patterns for brightness I couldn't get the two moving bars to even appear with my Barco's brightness setting all the way up. What I decided to do was bump up the brightness on the Panny to +6 with the brightness on the Barco near midpoint. This gave me the desired results with the Avia tests discs.

Question is: Is this OK. I mean the picture is better but will I damage anything? Should I go with the Panny's lighter setting and set the players brightness back to zero and just adjust through the Barco? The projector only runs dvd's no other sources? Funny thing is the blacker setting made colors in Monsters Inc look deep and rich but made Spiderman completely disappear in dark scenes.

Any help would be appreciated.

Andy
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post #26 of 26 Old 12-01-2002, 10:30 PM
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Originally posted by AndyN
Quick question for you all. I'm currently feeding my Barco 1208 with a quadscan pro connected to an interlaced signal from a Panny RP 82. I previously had it isf'd on a Sony DVP 7000. Following the manual I set the Panny to the blacker setting but like many others have noted my picture was just too darn dark. When I tried Avia's patterns for brightness I couldn't get the two moving bars to even appear with my Barco's brightness setting all the way up. What I decided to do was bump up the brightness on the Panny to +6 with the brightness on the Barco near midpoint. This gave me the desired results with the Avia tests discs.

Question is: Is this OK. I mean the picture is better but will I damage anything? Should I go with the Panny's lighter setting and set the players brightness back to zero and just adjust through the Barco? The projector only runs dvd's no other sources? Funny thing is the blacker setting made colors in Monsters Inc look deep and rich but made Spiderman completely disappear in dark scenes.
You probably will get more accurate results by turning the brightness back down and setting the black-enhance to light.
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