AVS Forum banner

Setting contrast with Spears and Munsil disc

48K views 483 replies 31 participants last post by  Mr.D 
#1 ·
Is there another pattern on this disc to set/verify contrast, other than the one labeled "contrast"? I'm having trouble getting the "contrast" test pattern to work correctly. Thanks.
 
#77 ·

Quote:
Originally Posted by dlarsen /forum/post/18474864


Here's one definition of what is valid in StudioRGB


All the (and only the) BTB/WTW triads are outside of this definition of valid. If they aren't classified here as valid, then what would that make them?


For YCbCr triads, there are much less that are valid (~2.8 million). YCbCr is recognized as have very poor valid codeword utilization.


Dave

This is the same semantic bulls**t you've been trying to play for years.
 
#78 ·

Quote:
Originally Posted by dlarsen /forum/post/18475260





Yes, I believe most all telicined material inherently starts out, or is placed early on, in StudioRGB space. I'm sure I'll be corrected if I'm wrong. This is the color space that Poyntons definition of valid is referring to. All excursions into BTB/WTW are excluded from his classification of possibly being valid.





Dave


I regularly handle telecined material and its never been clipped to 235 in RGB.
 
#79 ·

Quote:
Originally Posted by dlarsen /forum/post/18475260


OK. The quote and my response here has made no reference to what is or is not present. Only what is classified by the Poynton quote as valid in StudioRGB.




Yes, I believe most all telicined material inherently starts out, or is placed early on, in StudioRGB space. I’m sure I’ll be corrected if I’m wrong. This is the color space that Poyntons definition of valid is referring to. All excursions into BTB/WTW are excluded from his classification of possibly being valid.




If the WTW StudioRGB space (235-254) is, or is supposed to be used for valid, intended, extended video information, why can’t they excurse in unison? Why would any excursion into StudioRGB WTW be specifically excluded from the definition of valid color triad?




Again, I’m not arguing if it exists or not, or how much, or what it is, (but I can), I’m just pointing out that by the referenced Poynton quote, any and all BTW/WTW triads in StudioRGB (individually or in unison) are specifically excluded from being classified as a valid color pixel triad.


Being able to utilize the entire BTB/WTW range is a huge issue for calibration vendors. I do understand that.


Dave

Actually, Poynton doesn't really refer to R'G'B' as being "valid" or not at all, because it's kind of redundant. He only refers to R'G'B' signals as being "legal." A different term, "valid" is only useful when you move to Y'CbCr space where we have to distinguish what signals are appropriate within that space ("legal") and then what those signals represent in R'G'B' space ("valid/not valid")


The standards explicitly allocate this range for video, and it's quite useful. For instance, you can't make a non-neutral white without excursion beyond reference white. That's something that you cannot do in sRGB without lowering the luminance of the white point in such a scene.


You've been asked for years why you have such a problem with studio levels, and what benefits would be gained by clipping them off, and you have never come up with any reasonable answer for that.


It gets old when you continue reposting the same crap over and over, and when you won't answer anybody's questions.
 
#80 ·

Quote:
Originally Posted by sotti /forum/post/18475486


You simply clip the values to legal numbers, all values out of gamut are mapped to their nearest in gamut equivelent.


All though all that out of gamut data is what will be used to extend the gamut with xvYCC.


If StudioRGB is THE standard and YCbCr is just a transport mechanism, then there really isn't even a need to calibrate higher than 235.

If YCbCr is THE standard, then you need to calibrate all the way to 254(5).


There has to be a standard right?

And even if we're talking pure 'Studio RGB' you'd still want to preserve all the way up to 254. If it's in the content, you want to see it. And most all content excurses beyond 235 in RGB. There is no positive reason to clip content at 235. You don't gain anything by doing that, which is why it usually isn't done.
 
#81 ·
Look there is a really easy way to sort this out...


Sample some BD/DVD and see if it contains level outside 235 in RGB ( this has actually been done by S&M amongst others)


See if the picture looks better with the display white point mapping 235 or mapping 255.


Rinse/repeat etc.
 
#82 ·
Just checked some NTSC material off D1.


Its clouds in bright daylight with the sun visible . Not the nicest material in the world looks like old timelapse stock footage telecined from film.


Level tops out at 254 RGB.


If I clip it at 235 and drag 235 up to 254 to mimic the display criteria of the original material...looks truly awful.


this is on a rec 709 lutted workstation
 
#84 ·

Quote:
Originally Posted by sotti /forum/post/18475174


I somewhat disagree. Obviously we can encode steps all the way to 254(5) for RGB in YCbCr, how else would we generate the ramps?


But even though 16-235 are the only valid values for white, the chroma channels are valid through 240

Please note that I'm using your response as a bit of a springboard.


First: as I quoted CbCr is 16-240 (my emphasis).

Quote:
The digital representation shall be as defined in Part 1, Section 6.10 of ITU-R BT.709-5 and is summarized below:

The coding shall be 8-bit coding (scale of 0 to 255). R, G, B, and Y signals shall have 220 quantization levels with the black level corresponding to level 16 and the peak white level corresponding to level 235. The signal level may occasionally move beyond level 235. CBCR signals shall have 225 quantization levels with a zero level corresponding to digital level 128 and full range corresponding with 16 to 240. For R, G, B, Y, CB, CR signals, 0 and 255 are reserved and should not be considered video.

I don't choose to argue about or care much about technical minutia. I don't even care much what happens in post. I have no control over that. What I care about is what my equipment can do. And like any number of other bits of AV stuff it clips outside the STANDARD range. Yes, that's right, CEA-861-D is a standard followed by consumer electronics manufacturers world-wide. So my wonderful 9g Kuro monitor clips because Pioneer read the standard (it also obeys the quantization flags in 861/HDMI 1.3, possibly the only display to do so). My AVR used to clip (because you can program a REON to clip) until I convinced them it was a good thing not to clip.


All the obstruse technical arguments in the world are irrelevant unless they take operation standards into account.


Said standards are the reason for this and various other threads asking about "Setting contrast with Spears and Munsil disc" or any other reference material.


On the bright side these things can actuall be fixed (just join CEA) -- unlike all the crappy DVDs you own with bogus MPEG flagging and horked telecine.
 
#85 ·

Quote:
Originally Posted by bodosom /forum/post/18478066


Please note that I'm using your response as a bit of a springboard.


First: as I quoted CbCr is 16-240 (my emphasis).




I don't choose to argue about or care much about technical minutia. I don't even care much what happens in post. I have no control over that. What I care about is what my equipment can do. And like any number of other bits of AV stuff it clips outside the STANDARD range. Yes, that's right, CEA-861-D is a standard followed by consumer electronics manufacturers world-wide. So my wonderful 9g Kuro monitor clips because Pioneer read the standard (it also obeys the quantization flags in 861/HDMI 1.3, possibly the only display to do so). My AVR used to clip (because you can program a REON to clip) until I convinced them it was a good thing not to clip.


All the obstruse technical arguments in the world are irrelevant unless they take operation standards into account.


Said standards are the reason for this and various other threads asking about "Setting contrast with Spears and Munsil disc" or any other reference material.


On the bright side these things can actuall be fixed (just join CEA) -- unlike all the crappy DVDs you own with bogus MPEG flagging and horked telecine.

And the Kuro is wrong. There are many consumer displays that don't clip, as they shouldn't. NO professional displays clip like this, and studios don't set up their displays to clip this way.


It is asinine for you to say you only care what consumer devices do, and that you don't care what studios do. These are studio standards, and it is the practices of studios that are of crucial interest to anyone who cares about image fidelity. And nowhere do studio standards state that anything should clip to 16-235. On the contrary they imply quite the opposite.


The list of consumer devices and displays that regularly and continually and consistently screw things up (including the Kuros) is endless. If your bar for image quality is what an average consumer device does, then that is a VERY low bar indeed.
 
#86 ·

Quote:
Originally Posted by ChrisWiggles /forum/post/18478213


And the Kuro is wrong ... It is asinine for you to say you only care what consumer devices do ...These are studio standards

I'm going to ignore this bit of unpleasantness are reiterate my point. There are STANDARDS (as in printed documents) that consumer electronics companies (like Pioneer) can follow. Amazingly even intelligent people can read an ambiguous document and come to disparate conclusions. Where CEA standards and SMPTE Recommended Practice papers diverge there are going to be problems. But pretending that CE companies don't have a basis for their decisions is simplistic.


By the way I don't care what studios and post houses do -- good or bad -- because I can't change it. If I purchase a some AV gear with idiosyncratic behavior I don't like then I can do something. Just like I don't care about the feud between you and dlarson. There's nothing I can do about it either (however I suggest that if you two can agree that Poynton is the authority then send mail to his question/answer address at SpectraCal and have him resolve the issue).
 
#87 ·

Quote:
Originally Posted by bodosom /forum/post/18478362


There are STANDARDS (as in printed documents) that consumer electronics companies (like Pioneer) can follow.

That's right. And still they manage to screw things up with impressive regularity.


It took nearly a decade for many manufacturers to figure out how to handle chroma with progressive-scan DVD players correctly. And it is STILL commonly screwed up.


It's taken them practically a generation to figure out how to decode NTSC accurately.


The reference is the studio. Period. That is where we discern the artistic intent, and that is the image we are attempting to reproduce.


Consumer devices are often a cruel joke in comparison.


The Kuro is wrong, and it is unfortunate. It's not surprising though: it's not a professional display.
 
#88 ·

Quote:
Originally Posted by ChrisWiggles /forum/post/18478428


...


The reference is the studio. Period. That is where we discern the artistic intent, and that is the image we are attempting to reproduce

....


The Kuro is wrong, and it is unfortunate. It's not surprising though: it's not a professional display.

Well only the film maker gets to see the truth then unless you're suggesting that what comes out the DVD/BD production house is the same as what's on the film. And don't be so quick to blame CE companies. Anyone can look at a DVD and see that it's rife with MPEG errors because of bad encoders or pilot error.


Actually Pioneer tried diligently to do the right thing. They include a switch that turns off clipping and as I said they're the only company I'm aware of that properly processes quantization information in AV Info frames.


And finally I don't think pro/reference monitors can realistically be used as a model of behavior. And not because not even Runco has the nerve to charge $30k for 17" display but because the monitor is just one part of the production chain addressed by SMPTE RPs.


It goes without saying that none of this provides any help to the OP anyone else asking how to "fix" their problems.
 
#89 ·

Quote:
Originally Posted by bodosom /forum/post/18478362


By the way I don't care what studios and post houses do -- good or bad -- because I can't change it.

My understanding is that the only reason we calibrate our displays at all is to emulate what the post houses do.


Calibration in it's purest form is intrinsictly about what the post houses do.
 
#90 ·

Quote:
Originally Posted by bodosom /forum/post/18478583


Well only the film maker gets to see the truth then unless you're suggesting that what comes out the DVD/BD production house is the same as what's on the film.

Increasing film makes view the DVD/BD release as the definitive version of their works. They are there in post making tweaks and changes.


Abyss was recently brought to my attention as a film that was lit completely different in the movie house (tungsten daylight look) then on video (the blue tinted movie we remember).


I listened to Ron Moore talk about making BSG and how he frequently made decisions slanted toward the version that will persist after airing (BD).


George Lucas clearly views the most recent DVD release of SW as the most canonical.
 
#92 ·

Quote:
Originally Posted by Jim McC /forum/post/18478659


I'm sorry I started this ridiculous thread. And the worst part is I still don't know how to find the proper contrast setting.

THX says


1) NO CLIPPING!

2) No discoloration

3) No eye fatigue.



They don't even list maximizing brightness or comprimise on any of the above for better light output.
 
#93 ·

Quote:
Originally Posted by sotti /forum/post/18478595


My understanding is that the only reason we calibrate our displays at all is to emulate what the post houses do.


Calibration in it's purest form is intrinsictly about what the post houses do.

I'll disagree (no disrespect). As far as I know the only clear and unambigous standards we calibrate to are black level, white point and gamut. The other bits (max output and gamma) which are enormously important (hence this thread) are fluid items that inspire more heat than light (especially if you own plasma badumdum). This is another reason why I might say to the OP don't worry, be happy. I'd rather clip at reference than have a display I can read by at 0% and is unable to even see 2.2 from where it's standing.


By the way, if you calibrate for old-school black and white raise your hand.
 
#94 ·

Quote:
Originally Posted by Jim McC /forum/post/18478659


... the worst part is I still don't know how to find the proper contrast setting.

There isn't one which is why you don't know how to find. If you want optimal settings you should hire a pro that will work with you toward that end.

Quote:
If it isn't clear yet ... there is reference and then there is preference.
Quote:
My advice in these situations is to try it and see what you prefer.
Quote:
But setting Contrast is more subjective

You can keep asking but the answer won't change.
 
#95 ·

Quote:
Originally Posted by sotti /forum/post/18478641


Increasing film makes view the DVD/BD release as the definitive version of their works. They are there in post making tweaks and changes

That's totally a shame since home reproduction is just a pale shadow of a quality theatrical experience. However ... follow the money.

Quote:
....

George Lucas clearly views the most recent DVD release of SW as the most canonical.

Feh, every time someone watches the "fixed" version a puppy dies. That observation is cognizant of limitations that pass with time. My introduction to the world of post was Se7en. The best DVD "extras" ever. David Fincher essentially remade the film in post for DVD because he ran out of money while making the theatrical release.
 
#96 ·

Quote:
Originally Posted by bodosom /forum/post/18478583


Well only the film maker gets to see the truth then unless you're suggesting that what comes out the DVD/BD production house is the same as what's on the film. And don't be so quick to blame CE companies. Anyone can look at a DVD and see that it's rife with MPEG errors because of bad encoders or pilot error.


Actually Pioneer tried diligently to do the right thing. They include a switch that turns off clipping and as I said they're the only company I'm aware of that properly processes quantization information in AV Info frames.


And finally I don't think pro/reference monitors can realistically be used as a model of behavior. And not because not even Runco has the nerve to charge $30k for 17" display but because the monitor is just one part of the production chain addressed by SMPTE RPs.


It goes without saying that none of this provides any help to the OP anyone else asking how to "fix" their problems.

The world is full of compromises, and there is no perfect medium or ideal. However, what is seen in the mastering bay is usually what the filmmaker intends. In the old days, there was some distance between what was mastered pure on film, and then afterwards what was telecined for broadcast, DVD, etc. Today, nearly everything gets a DI, so what the director, DP, etc see is really the same thing that gets printed back to film, and that's often the same thing that gets slightly adapted for HD or SD distribution as well. And in a lot of cases, what you are seeing on say BD may actually be closer to what the director saw when making the film than what you see in an average multiplex film print which can often look pretty cruddy.


The reference is always as close as we can get to the original artistic intent, and the best referent we have for that is the master.
 
#97 ·

Quote:
Originally Posted by Mr.D /forum/post/18475586


Just checked some NTSC material off D1.


Its clouds in bright daylight with the sun visible . Not the nicest material in the world looks like old timelapse stock footage telecined from film.


Level tops out at 254 RGB.


If I clip it at 235 and drag 235 up to 254 to mimic the display criteria of the original material...looks truly awful.


this is on a rec 709 lutted workstation

Are you saying if I pop in a DVD or BD movie and look for a bright scene like the one you describe and toggle super-white on and off on my PS3 I'd actually see a difference? Anyone have good examples for this purpose?
 
#98 ·

Quote:
Originally Posted by PlasmaPZ80U /forum/post/18479443


Are you saying if I pop in a DVD or BD movie and look for a bright scene like the one you describe and toggle super-white on and off on my PS3 I'd actually see a difference? Anyone have good examples for this purpose?

less likely if you are output YCbCr instead of RGB.


Most of the issue revolves around the fact that calibrating your TV happens in RGB space because the pixels are physically red blue and green. But the content is in YCbCr space and legal YCbCr values map to values greater than 235 already.


actually an interesting test would be if you got a Red, Blue or Green ramp and toggled superwhite on and off where the cutoff would be for what you could see. With superwhite on you should be able to see to 254, with superwhite off, you'd likely still be able to see >235. But on a grayscale ramp that without superwhite it would clip at 235.
 
#99 ·

Quote:
Originally Posted by sotti /forum/post/18479514


less likely if you are output YCbCr instead of RGB.


Most of the issue revolves around the fact that calibrating your TV happens in RGB space because the pixels are physically red blue and green. But the content is in YCbCr space and legal YCbCr values map to values greater than 235 already.


actually an interesting test would be if you got a Red, Blue or Green ramp and toggled superwhite on and off where the cutoff would be for what you could see. With superwhite on you should be able to see to 254, with superwhite off, you'd likely still be able to see >235. But on a grayscale ramp that without superwhite it would clip at 235.

Using the high RGB clipping pattern on the AVS disc, green flashes to 251 (the highest bar in the pattern). Blue and red seem to be clearly visible only up to 243.


With super-white on, all three go to 251.
 
#100 ·
The most precise way I've found to set contrast is from the M&S disk, though not with the numbered panels, but with the pattern above them. With Cst too high, one clearly sees two bright vertical bands, and as one lowers it the two bands merge into one. The right setting is just when they merge. With this setting I can see the white bars up to about 251 or so. (On my RS20, with the Expanded HDMI setting, this gives Cst = 6, and Br is -5.)
 
#101 ·
I generally use the AVSHD disc and set contrast so that 253/254 are discernable and also that the contrast is not so high that its clipping any of the color channels. ( this part I usually set by eye and then verify with Calman when I calibrate grayscale)


My panasonic plasma will not clip at any contrast setting but it will knacker gamma and grayscale if its too high. You can get white to clip if you change the signal level setting.


My RS1 will clip with the contrast control in a fairly standard manner.


Every broadcast monitor I've bothered to check recently shows white level all the way up to 254.


I can normally tell when I'm watching something (DVD/BD) on a display that is clipping at 235. Like I said try it and see rather than continually discussing it.


In fact my old ancient panasonic DVDA350 (still works fine) always clipped everything below 17 but kept everything up to 254. I guess someone was being sensible by chucking out what wasn't needed to maximise the bitdepth in the processing pipeline for an early player.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top