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BT.1886 - a question?

post #1 of 63
Thread Starter 
As BT.1886 is not in use for any mastering (that I am aware of, and certainly not by any post-house I work with, which is a lot...), why the interest in using it to calibrate home displays?

Just wondering...

Cheers.
post #2 of 63
Maybe it gives a better guidance on gamma? Most prosumers have no idea of what BT.709 is let alone BT.1886!
post #3 of 63
So I've thought about this for reviewing displays, and my thoughts have been:

- There is no other "standard" gamma to use, so I can either pick one out of a hat for the target, or I can use the only actual standard there is
- Studios might start using it, in which case if I bought a display I'd want it to be able to do it
- Maybe if enough people push for it, we will get support for it (preferably through a 10-point grayscale on every display)

For most reviews on projectors, I aim for a 2.35 gamma or so for my space, but I always wonder about that as most people probably don't have as controlled a room as I do, so maybe I should target 2.2 for more general use? Using BT.1886 gives me a reason to use a target value, since it is a standard, though production houses might not use it. I always get totally different answers when I ask people what production houses yet, some will say 2.2, some 2.4, some 2.6, I never get the same answer from anyone.
post #4 of 63
Quote:
Originally Posted by Light Illusion View Post

As BT.1886 is not in use for any mastering (that I am aware of, and certainly not by any post-house I work with, which is a lot...), why the interest in using it to calibrate home displays?
Just wondering...
Cheers.

In addition to smackrabbit's points, there does seem to be some benefit to using BT1886 on displays (cough LCD's cough) that have stupendously bad black levels (compared to CRT tech) even given the obvious risk of getting a double dose of "shadow detail boost."

Remember that if you set BT1886's Lb parameter to zero, you essentially have power law with gamma = 2.4.

Perhaps one should experiment a bit to see what BT1886 actually does ... even for current titles? smile.gif
post #5 of 63
Gamma is always a moving target. Some even find 2.2 too dark for their likings for certain films. Since most out of the box consumer TV's measures around 2.0, maybe studios are mastering on a low gamma so it looks better for the masses? Even worse, low budget material maybe mastered on uncalibrated monitors with low gamma!
post #6 of 63
I find the target gamma standard issue a incredible one.

I come from a photography/ science background for my understanding of colour/ gamma/ calibration, etc and it's just common knowledge.
Profile your display for 2.2 Gamma and D65 whitepoint. simple.

but you got to video/ film where you run into a huge range of creative people (directors, producers, etc) who all want a certain look to their film/ show and are pedantic about the lighting/ colours and angles and all that creative jazz,
then they spend mega bucks in post productyion getting it right..

But don;t inform anyone what they need to do to their displays to view is as it was intended.

lets hope they see the light and actually use and agree on one single standard.
Or is that not artistic enough and being conformist so it must be bad and they will lose artistic credit...
post #7 of 63
Quote:
Originally Posted by Robbks View Post

I find the target gamma standard issue a incredible one.
I come from a photography/ science background for my understanding of colour/ gamma/ calibration, etc and it's just common knowledge.
Profile your display for 2.2 Gamma and D65 whitepoint. simple..

Yes and no:

1) Simple in the fact that for many, many years there really wasn't much the "home viewer" could do about "gamma." ... If you had a CRT, chances are you got something sort of resembling a "power law" curve with a gamma ranging between 2.0 and 2.6, depending upon where you measured, and probably averaging somewhere around 2.4.

2) Simple in the fact that even on most modern displays (those with only 2pt or worse 1pt CUTs and DRIVEs) you're not going to be able to implement BT.1886 anyway. smile.gif In this case, a power-law gamma of 2.2 with a linear offset black level compensation* is probably the best you can do to approximate the BT.1886 function ... depending upon how bad (or good) your black level is. *Oops, just realized you'll need at least a 10pt WB for that too.

A word of advice, from someone that's "been there," before one launches a knee-jerk, reactionary assault upon the first actual "gamma" standard ever, perhaps one should first should investigate it, perhaps even experiment with it on real world displays ... particularly one with poor black levels where it would make the most difference. smile.gif

PS: It's probably time to stop calling it "Gamma." Gamma is the name of the power-law exponent parameter, not the name of the function. smile.gif
post #8 of 63
Quote:
Originally Posted by Light Illusion View Post

As BT.1886 is not in use for any mastering (that I am aware of, and certainly not by any post-house I work with, which is a lot...), why the interest in using it to calibrate home displays?
Just wondering...
Cheers.

I think I disagree with your basic premise above that noone is using Rec. 1886 for mastering.

I posted a poll here back in Sept. 2009 (before Rec. 1886 was finalized) asking folks with experience in BD/DVD authoring what display/decoding gamma was typically used by the industry for mastering, and ~2/3 of the respondents selected either the "2.2 to 2.5" option or something in the 2.35 to 2.40 range. The other ~1/3 chose 2.2 or 2.22. (Unfortunately, the poll now seems to be broken due to the AVS update, so you'll have to accept my word on the above.)

While far from definitive, the results suggest to me that the display gamma used for mastering in Region 1/A was (and probably still is) pretty well in line with the EBU/Rec. 1886 recommendations of 2.35 and 2.40.

2.2 was the old NTSC encoding standard. Although it was also widely adopted by the PC industry, IMHO, it was never intended as a standard for displays in the video industry (because that would have resulted in an end-to-end gamma close to 1.0 or "unity"). Research like this study also suggests to me that typical CRT display gamma in the days of NTSC was probably also pretty close to the 2.40 value recommended in Rec. 1886.
Edited by ADU - 7/6/12 at 8:28pm
post #9 of 63
Quote:
Originally Posted by ADU View Post

I posted a poll here back in Sept. 2009 (before Rec. 1886 was finalized) asking folks with experience in BD/DVD authoring what display/decoding gamma was typically used by the industry for mastering...

...Unfortunately, the poll now seems to be broken due to the AVS update...


 

I did some digging in my old notes and fwiw these were the poll results as of 5/17/11 (poll was originally posted 9/24/09)...

Poll Question: What decoding gamma does the R1 film/TV industry typically use for BD/DVD mastering?

Total Voters: 38

62252


 

Choices: Votes: Percentage:
2.20 8 21.05%
2.22 5 13.16%
2.30 1 2.63%
2.35 3 7.89%
2.20 to 2.50 (2.35 average) 16 42.11%
2.40 3 7.89%
2.20 to 2.60 (2.40 average) 1 2.63%
2.45 0 0%
2.50 1 2.63%
2.60 0 0%


Poll discussion thread.
 

 

 

POLL3.PNG 11k .PNG file
Edited by ADU - 7/7/12 at 4:24pm
post #10 of 63
Did anyone here watch Night Train to Lisbon ?

Well after lots of 3dluts created using power law 2.2 black poin compensation and bt1886, my personal opinion is that almost all movies has something "wrong" when watched on a display calibrated with BT1886 gamma on a limited contrast display (say below 2.000:1, and I know many experts will disagree!). Shadows are fully intelligible but they appear to me too raised, and in some very dark scenes shadows are so high to the point that there's no coherence with the amount of light on the set. A good example is the light of candles in relation with the shadows projected.

But.......finally I found a movie, recently shoot, that definitely appears correct only with BT1886 . It's the only movie that gives me this impression with no doubt at all. Now since it's very recent, I'm wondering if the reason of my impression is that the movie has been actually graded according to BT1886.

I know that director of photography could have wanted to give a certain look, but I picked up scenes, that watched at gamma 2.2, let disappear completely a person in the dark in the foreground, hard to sustain that it's an artistic choice.... while if watched with 1886...perfect!!!!

I invite everyone who actively participated in the others bt1886 discussions, to watch this movie......with both bt1886 and 2.2 gamma power law.
Edited by Kukulcan - 2/6/14 at 9:26am
post #11 of 63
Quote:
Originally Posted by HDTVChallenged View Post

In addition to smackrabbit's points, there does seem to be some benefit to using BT1886 on displays (cough LCD's cough) that have stupendously bad black levels (compared to CRT tech) even given the obvious risk of getting a double dose of "shadow detail boost."

this.
post #12 of 63
While this is an old thread, reading some of the earlier replies. I don't quite understand something. Some say BT.1886 is to help displays with poor black levels. Then that is just going to make them even cloudier... no?

Kukulcan, have you seen Man of Steel? I've found flat line gamma 2.2 with black compensation crushing blacks in that film. Superman's hair is solid black in just about every scene. More so with bright whites glaring through. Can't see any highlights on any partial black sheen. With BT.1886 you can pick up the faint highlights even though it's still very deep. Tron Legacy is another when it comes to the females black hair. 2.2 is so dark you can just barely see the strands.

From so many threads, forums, so many people have such different tastes in black levels. Plus I keep reading so many say 2.2 is foggy while others say 2.3 and higher is great. They must be used to crushed blacks?...

I've read here that even some people with high end plasma's has said 2.2 is extremely dark.

I haven't seen a film yet where I've found BT.1886 cloudy or crushed with average gamma 2.26.

The only oddity I have found with BT.1886 is with such old films like Batman 89 with the Batwing scenes and the matt paintings. It shows up like a child holding a toy in front of a TV even though it's not cloudy. Like the 60s/70s look where the camera is in front of the windscreen with the fake action taking place around the windows.

Though, I'm amazed how good Predator looks with BT.1886. Very rich dark detail in some of the dense jungle scenes while sitting talking/hiding and bunched up.
post #13 of 63
Quote:
Originally Posted by xvfx View Post

While this is an old thread, reading some of the earlier replies. I don't quite understand something. Some say BT.1886 is to help displays with poor black levels. Then that is just going to make them even cloudier... no?

Read through my post here. It explains how this all works:


p.s. didn't even realize how old this thread was until you mentioned it!
post #14 of 63
Oh yes, I picked this old thread up, already too many discussions about 1886...

No xfvx, I haven't seen Man of Steel... But you may be referring something similar to my impressions about train to Lisbon....

Thanks spacediver for your insights, but pls note that I'm saying something a little different...

I mean.... I found a movie that has turned upside down my impression about bt1886, and I suppose that the reason could be the adoption of bt1886 recommendation by who graded the movie.
That movie simply appears perfect with bt1886 and clipped/hyper contrasty with power law; no other movie I saw gave me the same impression
post #15 of 63
i have recently updated my version of calman 5 and with the new update came some info about BT1886. something i was completely unaware of until 5 days ago. i have my ST60 calibrated to a very flat smile.gif 2.2 power. its only a hobby for me so sometimes when something new pops up for me like this it takes some time to separate fact from fiction, if in fact there is a right way to do it and its not just based on personal opinion. this may seem pretty basic. My basic understanding of gamma was that a lower gamma of less than 2.2 would expose more detail on the low end and effectively lighten the black portion of the video signal and wash out the picture (low contrast). a high gamma of more than 2.2 would "crush" the detail in the black portion of the video signal but darken the black level at the expense of the detail. where i am confused is where i have read people saying that bt1886 is alot like using a 2.4 power function. is this true? I can't think that it is because most people agree bt1886 helps increase black detail on the low end on more current material. can anyone help explain this to me? either way i will probably take another stab a calibrating my set and see. i have been thinking that its been a while since i last saw man of steel. smile.gif
post #16 of 63
As I understand it, it is 2.4 until you get to the darker part, where is gradually raises gamma (to a lower number) to make sure you get proper detail in lower levels. It actually takes the minimum blacklevel and maximun contrastlevel of your display and calculates the 1886 curve from that
post #17 of 63
Quote:
Originally Posted by Wouter73 View Post

As I understand it, it is 2.4 until you get to the darker part, where is gradually raises gamma (to a lower number) to make sure you get proper detail in lower levels. It actually takes the minimum blacklevel and maximun contrastlevel of your display and calculates the 1886 curve from that
ok this makes sense. i guess i can expect to see calman want to read the max and min at some point before asking me to adjust gamma. i'll try it out tonight and see how it looks. since this is my second plasma with solid black levels im curious to see how much of a difference it makes. might have to calibrate a friends lcd after to compare. ill post back with my findings for anyone who might be interested.
post #18 of 63
Quote:
Originally Posted by denide View Post

Quote:
Originally Posted by Wouter73 View Post

As I understand it, it is 2.4 until you get to the darker part, where is gradually raises gamma (to a lower number) to make sure you get proper detail in lower levels. It actually takes the minimum blacklevel and maximun contrastlevel of your display and calculates the 1886 curve from that
ok this makes sense. i guess i can expect to see calman want to read the max and min at some point before asking me to adjust gamma. i'll try it out tonight and see how it looks. since this is my second plasma with solid black levels im curious to see how much of a difference it makes. might have to calibrate a friends lcd after to compare. ill post back with my findings for anyone who might be interested.

Hello, you will need 10-Point Gamma Controls to handle the different gamma value targets you may have to your every Grayscale Step.
post #19 of 63
Quote:
Originally Posted by Wouter73 View Post

As I understand it, it is 2.4 until you get to the darker part, where is gradually raises gamma (to a lower number) to make sure you get proper detail in lower levels. It actually takes the minimum blacklevel and maximun contrastlevel of your display and calculates the 1886 curve from that

Reference BT.1886 plot for my ST60 starts with 2.25 at 10% stimulus and ends with 2.36, it never goes up to 2.4 )...that said, it appears too dark on almost everything...2.2 gamma with black compensation looks more correct to my eyes...begininning to wonder if BT.1886 is at all fit for displays with very low MLL...
post #20 of 63
Quote:
Originally Posted by denide View Post

i have recently updated my version of calman 5 and with the new update came some info about BT1886. something i was completely unaware of until 5 days ago. i have my ST60 calibrated to a very flat smile.gif 2.2 power. its only a hobby for me so sometimes when something new pops up for me like this it takes some time to separate fact from fiction, if in fact there is a right way to do it and its not just based on personal opinion. this may seem pretty basic. My basic understanding of gamma was that a lower gamma of less than 2.2 would expose more detail on the low end and effectively lighten the black portion of the video signal and wash out the picture (low contrast). a high gamma of more than 2.2 would "crush" the detail in the black portion of the video signal but darken the black level at the expense of the detail. where i am confused is where i have read people saying that bt1886 is alot like using a 2.4 power function. is this true? I can't think that it is because most people agree bt1886 helps increase black detail on the low end on more current material. can anyone help explain this to me? either way i will probably take another stab a calibrating my set and see. i have been thinking that its been a while since i last saw man of steel. smile.gif
BT.1886 is dependent on your black/white measurements as Wouter73 said. Only if your MLL is very close to 0 will it be a lot like a 2.4 power gamma, and a reference black level will give you a 2.4 power gamma.
Edited by rahzel - 2/23/14 at 1:36pm
post #21 of 63
Quote:
Originally Posted by mytbyte View Post

Reference BT.1886 plot for my ST60 starts with 2.25 at 10% stimulus and ends with 2.36, it never goes up to 2.4 )...that said, it appears too dark on almost everything...2.2 gamma with black compensation looks more correct to my eyes...begininning to wonder if BT.1886 is at all fit for displays with very low MLL...


There are almost no sources mastered using BT. 1886. I find BT. 1886 looks absolutely terrible for the older (pre 2013 smile.gif) movies that I watch. I use a 2.25 gamma with black compensation.

Larry
post #22 of 63
Ive just found the high contrast gamma with dark blacks works better on my tv(budget Sam plasma).One reason is the tv looks washed out often...On this tv some of the programs(sports,new shows) have the dark crushed blacks, luminous whites that I can't really adjust out with 2 point or brightness.My as well just have all shows with dark black levels.At least it's consistent.
post #23 of 63
Quote:
Originally Posted by mytbyte View Post

Reference BT.1886 plot for my ST60 starts with 2.25 at 10% stimulus and ends with 2.36, it never goes up to 2.4 )...that said, it appears too dark on almost everything...2.2 gamma with black compensation looks more correct to my eyes...begininning to wonder if BT.1886 is at all fit for displays with very low MLL...

Sure it is. The problem here is that there's a whole era's worth of digital transfers that were "graded" on monitors set to power-law @ ~2.2 to 2.3 gamma.

The sad part of this is that most of that "very low MLL" potential winds up being wasted when you "flatten out" the gamma to 2.2ish. .... YMMV wink.gif

PS: Furthermore, you've probably become accustomed to how things look with PL @ 2.2, perhaps if you switched to BT1886 and left it there for a few days (or weeks) you might become accustomed to the "new" look. OTOH, BT1886 + the affects of ABL might make things too dingy on plasma. I confess, I've never tried BT1886 on a plasma ... mostly because I don't have one. wink.gif
Edited by HDTVChallenged - 2/23/14 at 11:54pm
post #24 of 63
the main issue I have with BT1886 is actually human faces getting garish and bit "under-exposed"...used GCD APL patterns that gave me the least ragged initial gamma response that I then worked from... however, I do try hard to give it a chance with any bluray...seems the latest releases are better in that regard, but anything from broadcast looks too dark in lows and midtones...as expected, I'd say...
post #25 of 63
so i after alot of reading and some of the input and explanation on this thread i completed a re calibration of my ST60 with BT1886 as my target gamma. First problem i will tell everyone about is the error 66 that i experienced with calman and my i1pro while trying to take a 0 stimulus reading. the error speaks to the sync setting for the meter and tells me to make sure it is set to "ON" (which it was). after some research i found that the "low light handler" option under meter settings needed to be enabled to get a reading which by default it wasn't. after that i took the rest of the readings and it gave me my target gamma curve. the curve it set for me went up quickly from zero to ten and i found that the IRE10 was probably a little below 2.2 which we could say for arguments sake is 2.15 and the high end it looked to be a little over 2.3. i watched a couple of scenes from some bluray movies that were released around 2011 to test. my choices where Transformers 3 for some hi gloss CGI a movie that is know to have a contrast that runs a little hot. my second choice was the most recent Robin Hood adaptation which has a few murky and dark scenes lit by fire or candle light to look at the low end. i finished off by watching most of Man of Steel (not all i got too tired tongue.gif)the content did look decidedly different. i didn't have any problems with skin tones. overall i still found the amount of shadow and low light detail very pleasing during scenes that i would consider middle of the road for brightness. during the brightest scenes the shadow detail was a little harder to pick out if you were looking but it was still there and wasn't close to "crushing". on the plus side i will say that the picture seemed to be a little more "3D" and the color was just a amazing as it was after my 2.2 gamma calibration. overall i guess you could say im finding it difficult to verbalize what the difference is (with my experience being limited to only a few different sets and having only done the one BT1886). i will say that i do like it and will leave the settings for a week and enjoy and few more films before making a final decision.


post #26 of 63
It appears you are using the standard CMS page, and if so, you are calibrating for 100% Saturation and 75% Stimulus. If your ST60 is like mine, this means you are undersaturating the values below 100% and have hue errors in red. Getting these interior points right is a lot more important than getting 100% right, so if your Calman licensing level supports it, I would recommend doing a 10 point saturation sweep and looking at the interior values.
post #27 of 63
Quote:
Originally Posted by sawfish View Post

It appears you are using the standard CMS page, and if so, you are calibrating for 100% Saturation and 75% Stimulus. If your ST60 is like mine, this means you are undersaturating the values below 100% and have hue errors in red. Getting these interior points right is a lot more important than getting 100% right, so if your Calman licensing level supports it, I would recommend doing a 10 point saturation sweep and looking at the interior values.

That's a good point. Ill have to dig into calman and see if my version has that option.
post #28 of 63
just came across this quote from Charles Poynton's "Digital Video and HD: Algorithms and Interfaces. Second Edition." (2012) (p. 326)
Quote:
No matter what transfer function characterizes the display, it is economically important to encode image data in a manner that is well matched to perceptual requirements. The BT.1886 EOCF is well matched to CRTs, but more importantly, it i well matched to perception! The performance advantage of perceptual coding, the wide deployment of equipment that expects BT.1886 decoding, and the huge amount of program material already encoded to this standard preclude any attempt to establish new standards optimized to particular devices.

A display device whose transfer function differs from a CRT must incorporate local correction, to adapt from its intrinsic transfer function to the transfer function that has been standardized for image interchange
post #29 of 63
Quote:
Originally Posted by spacediver View Post

just came across this quote from Charles Poynton's "Digital Video and HD: Algorithms and Interfaces. Second Edition." (2012) (p. 326)

Our Joel B and Charles were talking about this very subject last week in Palm Springs at the HPA retreat. Charles has some very interesting stories behind BT1886 and Rec2020.
post #30 of 63
It's definitely something I want to ask about if and when I meet him.
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