TV settings and bias lighting - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 26 Old 01-29-2020, 01:52 PM - Thread Starter
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TV settings and bias lighting

Does using bias lighting affect settings such as contrast, brightness, color and tint ? Are these settings done with bias lighting on or off ?

Thanks.
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post #2 of 26 Old 01-29-2020, 02:47 PM
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Yes and no.

Bias lighting is bull.

It effectively makes your iris contract more, but pump less, simulating more of a late day / evening viewing condition.

This affects color perception (you see more contrast) but does so subjectively - as they measure the same.

White ambient light should be close to D65 white (/= LED strip, usually) at about 10% of peak brightness conventionally.

But then you really are doing it the wrong way around.

So all CIE colorspace standards are specified for dark room environments. By adding bias lighting you change that, while still refusung to turn your TVs brightness down. Then you are picking up the legacy solution of some colorist that arguably didnt want to work in a tomb for living, so made up a scenario that allowed him to at least have a little light in the room (it was D65 mind you, so it didnt effect hist work, or so he told his boss ).

In reality - please - for gods sake - just turn the brightness (backlight setting of your tv usually) of the set down. I watch most of my content at a 80 nits target (while 100 is the default), and its plenty bright enough for my liking. Brightness is the element of color difference error you are least sensitive to, and your eye adapts contrast sensitivity all the time, so... Please pick a backlight setting that compliments your roomlight, and call it a day.

Now with HDR content you cant, because thats supposed to have a fixed gamma curve - at which point, yes - I guess buying bias lights makes sense, because its the only way you'll see colors as intended. (Room still pretty dark. LOL.)

At the last CES I believe Panasonic (?) introduced a 'daytime HDR mode', which they asked a few color grading professionals on which gamma curve ''came closest' so now even they are deviating from EOTF to meet demand. Samsung almost historically did so as well.. (But probably by what markeing saw was the best fit. )

Short answer is, you - as a consumer - dont need that much color accuracy, that you should start lighting the room differently, just so your eyes dont feel tired as soon.

Moviestheatres for the longest time where targeting between 55 and 75 nits. And even though a diferent grading process is involved, no one complained about that 20 nits difference even at the lower end of that spectrum.

If *person you trust* likes bias lighting should impact your decision to buy it less, than if you can stand watching your TV with the backlight turned down a little. Impact on color perception will be there - also, another calibration might/will be in order at the lower backlight setting, but the heck you are not designing your living environment around watching movies. And even if you were, using a bias lighting only ever follows best practice recommendations, not actual standards - I believe (that part I might be wrong on - the other stuff I know.. ).
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post #3 of 26 Old 01-29-2020, 07:41 PM - Thread Starter
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Whoa ! Thanks.
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post #4 of 26 Old 01-29-2020, 08:30 PM
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post #5 of 26 Old 01-29-2020, 09:53 PM
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Here the corresponding standards are discussed:
https://www.avsforum.com/forum/139-d...ing-smpte.html

Summery: Hodgepodge.

edit:
See also: https://www.avsforum.com/forum/139-d...nment-out.html

So I was wrong. Bias lighting now is in ITU and SMPTE spec, but not at 10% of peak white, but rather at a uniform 5 nits (so about 5% respectively).

Quote:
D65 ambient light level in the monitor environment surround "shall have" a luminance of 5.0 +/- 0.5 candellas per square meter (nits). This wording sets a formal standard, rather than the previous recommended practice of 10% of peak white displayed by the monitor. Coincidentally, the 5 nits surround illumination value specification aligns with recent statements by the ITU regarding usage for HDR mastering.
also:
https://www.lightillusion.com/viewing_environments.html

Which refutes what I said almost entirely. (But then in practice, .. )

edit: see also: https://www.avsforum.com/forum/139-d...dr-bright.html

edit2: Historical perspective:
https://www.avsforum.com/forum/139-d...l#post22115299
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post #6 of 26 Old 01-30-2020, 08:24 AM
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The best way is to watch in a dark room..

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post #7 of 26 Old 01-30-2020, 12:01 PM - Thread Starter
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Quote:
Originally Posted by Bruce2019 View Post
The best way is to watch in a dark room..
That's what I've always done, but then I wonder if I'm missing out on something, or is bias lighting BS !

The wall behind my TV is black, so would bias lighting even help ?
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post #8 of 26 Old 01-30-2020, 12:57 PM
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If you have to ask that question, its not for you. Unless you just want it anyhow.


I provided source links so people read them. (Im not copy pasting them in here just for lolz.)
If then in return a question to summarize from smartphone user comes in. Chances are that bias lighting is not what you are looking for.


So here is the deal.

1. Colorist not wanting to work in a tomb like environment still is the most likely/obvious cause for it being used at all.

2. SMPTE revising spec down to use 5 nits bias lighting instead of 10 nits max means "sh*t, 10 nits probably introduced perceived color difference" (but was previous spec for years).

3. Bias lighting being standard for HDR authoring in retrospect probably is also a good idea. While average scene luminance level only increased a little, having to work with 2000nits+ highlight details in a mastering scenario means, faster eye fatigue. Also you cant change max brightness down, or gamma at all in HDR mastering (EOTF is absolute, not relative), so resorting to bias lighting is the only thing you can do - really, if you need color accuracy and higher mastering productivity in that sort of environment. (It becoming more prevalent with HDR mastering makes sense.)

4. Spec in this case is designed by getting 5 grey beards in a room to agree on something. (Spec for room light condition varied all over the place in the past decade. Capabilities of TVs varied all over the place in the last decade. (Plasma TVs at one point werent even capable of 100 nits. No one complained.))

--

So ask yourself the following questions

- Do my eyes get tired when watching 100nits SDR content in a dark room?

If yes - am I happy, with turning down screen brightness and recalibrating (Screen Backlight / OLED light setting)?

If no - maybe invest in bias lighting.

- Do my eyes get tired when watching HDR content in a dark room? (Which I primarily watch.)

If yes - unless you are god tier calibrator with current get OLED set, you cant and shouldnt change HDR EOTF (rolloff/cutoff, or even more of the curve), so the only option is to get a bias lighting.
-


All of this is not applicable to 99.999999(whats the world population again)% of users.

No one in the history of TV manufacturing is expecting you to watch in a darkened room, if you are not a nerd that is single.

No one in the history of TV manifacturing is expecting you to control room light conditions when turning your TV on.

No one in the history of TV manufacturing is expecting you to source a D65 bias lighting source that you calibrate to 5 nits maximum, just so you can minimize iris contraction (less eye fatique).

For effing 7 years, people could not decide on if 80 nits, 100 nits or 120 nits should be the SDR standard (you did what you wanted) while some TVs where capable.

And all the SMPTE ever did is to increase the target for standard brightness arbitrarily to 120 nits - once capable devices came onto the market even as SDR was perfectly defined already.

With stuff like pupil dilation (amounts of rods and cones active on your retina) you get into psychovisual perception territory - and no one can give you a clear answer here at all.

The truth is, that no one other than color graders expects or works in that environment. No one cared to spec it out as anything but "best practice, with brightness dialed up to 120 nits as performance of screens incresed". And no one can say anything substantial against only watching the material at 80 nits either.

Yes there will be color difference. No, no one is keen to objectify and measure it. Subjectively its fine (but probably above JND (just noticeable difference).
-

You must be a very special breed of person to get it. (Perfection oriented, or. Anal retentive.) They guys who came up with the spec, had not your best interest in mind (or they would have kept it an unchanged standard for longer) - and for all I care wanted to get to a bar earlier when they defined a revision.

Vincent likes it though - and I can respect that as well.

But reasonably speaking - never, ever, ever get talked into something like that.

Especially if your mode of decision making is - SO I GOT ALL THOSE INFO, but guys - im an smartphone, can you break it down for me even more, whats best?

If you are that kind of person, and are asking 'if you are missing out'? - No, you arent.
---


Why can SDR be "relative" in that sense and HDR can not?

Our eyes only can cover a small range of contrast information, without adapting (Iris retracting, and contrast range shifting).

So for SDR you can shift that range around a little, because its intent is not to blind you - or make you squint or... And your eyes will adapt to that range accordingly. If you are watching in a dark room environment - at 100 or 120 nits though - because baseline is black environment, your irises will pump regardless - causing contrast perception differences everytime they do. So to minimize that (also with an impact on contrast perception), you can turn down screen brightness (you do on every laptop, and every smartphone, every day - without even thinking about it), or - as an alternative - you can introduce bias lighting (so your eyes never adopt to "dark room" levels, taking that range out of the occasion, making your irises pump less.).

On HDR every brightness level, and gamma is fixed - as that wonderful standard wants to play with the person watching a movie being blinded, or squiting, or being emotionally moved by a simple brightness effect. So the 'capability' to turn down screen brightness isnt in the standard. Flipside is, that you now get 100s of projector owners believing they also can do HDR, because marketing told them so, while their source device tops out at 120 nits (off of the canvas they are using). And HDR (home user) material currently is mastered to 1000 nits or 2000 nits standards. No one is talking reality into those people either.

They then use relative brightness, and turn down average image brightness level, to be blinded by an effect once in a while - and call that "tha HDR experience".

So they do on purpose, and willingly - what you are so reluctant to try to see how you like it.

Because somone fed you a buzzword, and now you think you need bias lighting.

In short I doubt it.

If you are a colorist - you currently are supposed to use it (especially on HDR ("Boss I have a headache again" (dark room mastering 2000 nits highlights) - goes into money real fast, if you are a production facility)), but you werent in the past.


The first thing you have to learn about this scene is, that someone is always trying to upsell you on something. And the goal is to get you to a point, where you can make informed decisions on your own.
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post #9 of 26 Old 01-30-2020, 01:41 PM
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If you think about it. While using bias lighting, you take

"your eyes adapting to dark room state"

out of the occasion (thats not happening anymore).


When you turn down the screen brightness for SDR material, you take

"your eyes adapting to peak light output"

out of the occasion (thats not happening anymore).


When you use HDR, you dont want to arbitrarily cut the top end, because thats your "effectiveness" for HDR (everyone is racing to 10.000 nits, yay!).
-


Your eyes contrast range is less than 0-100nits, so your iris will even adapt on SDR material, frequently. And everytime it does it changes your contrast perception (amounts of receptors on your retina firing).

Every time a cloud goes by the sun outside - your eyes and your brains do the same. So its pretty common for you to ignore the difference. Does it introduce perceptual color difference? Yes. Do you usually care? ("Ma Lamborghini isnt the same shade of orange anymore! Lets call customer support!!!1!11!") No.

Case for 80 nits being a posibility as a white target for SDR made.

Your eyes dont perceive a contrast range from 0-100 nits absolutely - they do so relatively. (So only ever see part (a subset) of it. And that changes dynamically with scene lighting.)

Ever seen the effect, that when a bright scene comes on on a LCD without perfect black level reproduction, black bars seem more black? OMG they changed color! (Thats your eyes switching contrast ranges.)

So how much do you need to forbid your eyes to do that to the fullest extent? 300 USD much? 500 USD much? 1000 USD much?

(Your usual LED strip will not output D65 (neutral) white. They are optimized for light output, not for matching mastering standard, so you are naturally paying a premium.)

Then take into account that peoples color perception varies, and that +/- no one watches TV in a darkened room in the real world, and you should have your answer.

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post #10 of 26 Old 01-30-2020, 02:17 PM
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Also, a brightness target for 100 IRE white is left out of the rec 709 standard. Intentionally.
SMPTE shifted recommendations from 100 nits to 120 nits - once capabilities arrived.
sRGB (web content standard, but more, every graphic item on your smartphone, TV interface, TV box, most photos you take, ...) was created with 80nits as the standard.
Movies historically where never screened at 100, or 120 nits.

So now it becomes a question of only using your TV for movie content that was probably designed by a color grading studio with bias lighting in the workflow - and this still not taking into account, that the more important 'pass' was done for cinema grade, and you not being able to know, how much the colorist actually changed that source.


If you know the standard filters that are used for that process, I'm interested to learn more..

Quote:
The wall behind my TV is black, so would bias lighting even help ?
No, the standard is D65 bias lighting onto a neutral white wall. Read the threads I linked.

(Smartphone users wanting to know whats best, because someone told them, they needed something, again... Managing their "Fear of missing out." is ever so fun. If that wasnt easy enough to digest, I apologize profusely ("Is it BS, or not?" > Practically, or theoretically?))

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post #11 of 26 Old 01-30-2020, 03:25 PM - Thread Starter
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Thanks. Because I'm not painting my black wall. I love it !
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post #12 of 26 Old 02-05-2020, 07:59 PM
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Well. i just tried out my MediaLight bias lighting strip (proper D65 and > 97 CRI). I watch movies in a dark room - as dark as i can get it.

Set it up for 10% using S&M Bias lighting pattern. TV is Samsung QLED 65' Q9FN.

Was sceptical with the results at first as preferred the dark room look but than ran a few pattern tests and watched a few things - and blacks certainly look deeper (and without losing shadow detail) with bias lighting. In both SDR & HDR so seems a win,

But, I still prefer the total darkness during dark scenes (ie cant see the TV frame etc) so still playing.
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post #13 of 26 Old 02-06-2020, 01:31 PM
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Lightbulb

Quote:
Originally Posted by Jim McC View Post
Does using bias lighting affect settings such as contrast, brightness, color and tint ? Are these settings done with bias lighting on or off ?

Thanks.
Bias lighting is not "bull" as claimed by a previous poster. The technique has been used and recommended by video experts and professionals since the days of black and white TV. It has also been consistently recommended for critical viewing and reference viewing environments for both mastering programs and evaluating display performance, by industry standards bodies world-wide, such as SMPTE, ITU, EBU, ISO, etc., etc.


A previous poster has made repeated references to most TV viewers not watching video programs in dark rooms. He is correct. TV manufacturers know this as well. However, most TV viewers aren't concerned about image fidelity and accurate program reproduction. Most TV consumers don't "sweat the details" when devoting time, money, and attention to their video experiences. They typically have no idea that there are standards and best practices used in the motion imaging industries to preserve picture quality and correct program reproduction, as well as provide extended viewing comfort in dark viewing conditions.



This is the display calibration section of the AVS Forum! Participants in the discussions and topics here are typically far more interested in technical details behind the how and why of video than the average TV consumer, as well as care about image fidelity and striving for accurate program reproduction. They aren't satisfied with making decisions about their home entertainment expenditures simply based upon advertising hyperbole, rumor, guesswork, intuition, popular notions, or anecdotal experiences.


In answer to your question, calibration of display parameters is best performed with bias lighting on, in an otherwise dark room. The same goes for a brightly lit environment. That is why some displays offer what is commonly referred to as "day and night modes" where settings are tailored for the differing viewing environment conditions.



Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
SMPTE, PVA, THX, ISF, Lion AV Consultants


"Advancing the art and science of electronic imaging"
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post #14 of 26 Old 02-06-2020, 03:04 PM
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Interesting posts by Harlekin. I disagree with some of it. But that’s ok! (Disclosure: my company makes the MediaLight and publishes Spears & Munsil, the former of which comes up in this thread). I’ve also learned a lot from GeorgeAB, who first got me turned on to bias lighting solutions.

Firstly, you are correct that bias lighting has literally no impact on the image on the display itself. As GeorgeAB has written so many times, the lights change how we see the picture by influencing human factors.

As for colorists and editors only wanting bias lighting to avoid headaches or to avoid walking into furniture, no doubt, headaches do fit into the equation. Our professional customers are not spending 8 hours or even 10 hours a day editing and color grading. In many cases it’s more like 16+ hours at a stretch. You might think that’s it’s better to watch in a dark room, and I suppose I watch in a dark room whenever I see a movie at the theater (on a reflective versus a transmissive display, however).

I’ve learned not to generalize and I’ve found that preference often trounces reference, at least in the marketplace. Sometimes available resources trounce both.

I’ve also discovered that people give and receive a lot of really bad advice and some companies sell really shoddy products. I’d argue that it’s better to not calibrate a display than to wing it and that poor ambient light sources can harm our perception of the image more than complete darkness.

However, what I’ve learned most of all is to find my own answers and to avoid shooting from the hip. There are so many opinions on boards like this and Reddit, yet there are industry standards and I suppose that it’s good, at a minimum, to know what those are and to understand when we diverge from them.

It might not make a big difference in the short term, or for one individual, but I can tell you from first hand experience, that when Apple switched the gamma profile in Snow Leopard from 1.8 to 2.2 (around 2009-2010) without documenting in their list of changes it resulted in very costly editing problems and disc reauthoring problems for my company when we were just starting out. Standards matter. Technology will always bite you in the rear end without them.

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Maker of The ISF-certified MediaLight 6500K Bias Lighting System

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post #15 of 26 Old 02-06-2020, 06:17 PM
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Quote:
Originally Posted by harlekin View Post
Yes and no.

Bias lighting is bull.
Now that I’ve got my kids home from band practice, I can dive a bit more into this.

I need to respectfully disagree. You might as well say that lighting is bull or that screen technologies are bull. Bias lighting is just room lighting that is placed in the ideal location for viewing — behind the screen.

If you’ve ever experimented on an iPhone or iPad with True Tone turned on or off, you can see how the ambient light in the room impacts the white point of the display. Your TV doesn’t adapt to the white point of the light in the room, this is why the light is matched to the CIE D65 standard illuminant.

Now, I’ll grant you that some post production facilities use the white point x=0.3067, y=0.3180) for their top emission RGB displays. We’ll make them for special orders, but they are very niche. Same goes for D93 (our Japanese dealer needed some, and I believe it’s a standard for mobile video in Japan). We’ve also made them with Judd Vos correction. However, after consulting with some of our clients in the professional world, they overwhelmingly preferred to stick with the D65 standard for backlight even if the display needed to be adjusted to get there.

Judd-Vos CMF is primarily employed on Top Emission RGB OLED. The whole point being to make them match a legacy reference CRT (and presumably by extension other display devices) operating at D65.

The basic premise for Judd-Vos CMF is that if there is significant energy below 460nm form the light source it may be a better CMF than CIE 1931. However, in practice we almost never find that customers calibrate LED based displays using Judd Vos CMF, it is almost exclusive employed with OLED — to match it to LED.

Either way we wouldn't match the bias light to the CMF of the display as they aren’t really related.

Keep in mind that a colorist wouldn’t simply be targeting the Judd OLED CIE 1931 equivalent target of 0.3067, 0.3180. They would then need to use a spectroradiometer loaded with a Judd-Vos CMF and match that to the reference light source. Which brings up another interesting point, is that a CRT, a CCFL bias light, daylight, etc. when you are talking about bias lights being bull? Your tale about the origin of bias lighting was during the era of CRT, no?

Anyway, the equivalent CIE 1931 values for that Judd obtained match will not be 0.3067, 0.3180, that would be unique to the spectral distribution of just top emission OLED.

I’ve spent (wasted) a LOT of time on alternate CMF bias lighting research and development so feel free to message me if you want to discuss this in more detail. My main objective is to not confuse customers with an option that, IMHO, doesn’t need to exist.

However, if you were to call bias lighting ”bull” when there are reference standards, ergonomic benefits and demonstrable viewing improvements, you would be wrong.

Quote:
Originally Posted by harlekin View Post



It effectively makes your iris contract more, but pump less, simulating more of a late day / evening viewing condition.

This affects color perception (you see more contrast) but does so subjectively - as they measure the same.

White ambient light should be close to D65 white (/= LED strip, usually) at about 10% of peak brightness conventionally.
If it was bull, it would not matter what color temperature it was.

Quote:
Originally Posted by harlekin View Post

But then you really are doing it the wrong way around.

So all CIE colorspace standards are specified for dark room environments. By adding bias lighting you change that, while still refusung to turn your TVs brightness down. Then you are picking up the legacy solution of some colorist that arguably didnt want to work in a tomb for living, so made up a scenario that allowed him to at least have a little light in the room (it was D65 mind you, so it didnt effect hist work, or so he told his boss ).

In reality - please - for gods sake - just turn the brightness (backlight setting of your tv usually) of the set down. I watch most of my content at a 80 nits target (while 100 is the default), and its plenty bright enough for my liking. Brightness is the element of color difference error you are least sensitive to, and your eye adapts contrast sensitivity all the time, so... Please pick a backlight setting that compliments your roomlight, and call it a day.

Now with HDR content you cant, because thats supposed to have a fixed gamma curve - at which point, yes - I guess buying bias lights makes sense, because its the only way you'll see colors as intended. (Room still pretty dark. LOL.)

At the last CES I believe Panasonic (?) introduced a 'daytime HDR mode', which they asked a few color grading professionals on which gamma curve ''came closest' so now even they are deviating from EOTF to meet demand. Samsung almost historically did so as well.. (But probably by what markeing saw was the best fit. )

Short answer is, you - as a consumer - dont need that much color accuracy, that you should start lighting the room differently, just so your eyes dont feel tired as soon.
You don’t need accuracy? Then why calibrate as you say 2 paragraphs down?
Quote:
Originally Posted by harlekin View Post

Moviestheatres for the longest time where targeting between 55 and 75 nits. And even though a diferent grading process is involved, no one complained about that 20 nits difference even at the lower end of that spectrum.

If *person you trust* likes bias lighting should impact your decision to buy it less, than if you can stand watching your TV with the backlight turned down a little. Impact on color perception will be there - also, another calibration might/will be in order at the lower backlight setting, but the heck you are not designing your living environment around watching movies. And even if you were, using a bias lighting only ever follows best practice recommendations, not actual standards - I believe (that part I might be wrong on - the other stuff I know.. ).
Out of this entire post, folks, remember one thing: The white point of the ambient light in the room impacts your perception of the display. If you think that tweaking the display is important, then I have news for you — the impact of chromatic adaptation on your perception of the screen is significant. You may prefer to be plunged into extreme darkness at the end of a scene, but preference is what it is. Heck, preference probably beats reference 80%-90% of the time, at least from most of the threads that I can get through.

I’ll agree to disagree on what you say you know to be “fact”, and I’m certainly not unbiased myself, but there are published bias lighting standards. It’s not just best practices. There is some disagreement about brightness levels, but we are also in a period where TVs have vastly different peak luminance and contrast ratios, so perhaps that’s not surprising.
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post #16 of 26 Old 02-06-2020, 09:09 PM
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Thanks GeorgeAB and ScenicLabs - I am slowly getting used to a not totally dark room when using bias lighting. Perception & Preference is important and I do like the deeper blacks bias lighting gives.

Only problem now is that I really like the look of the setup when the MediaLight strip is at 100% - looks very cool

Ok, I will desist
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post #17 of 26 Old 02-06-2020, 09:26 PM
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When I’m working on my computer (and, yes, we are working on a laptop bias light doohickey. that’s for another time), I’ll often set the lights at 100%. It would perceptually crush blacks into oblivion, but it makes it the screen easier on my eyes. From an eye strain perspective, this makes sense. From an image perspective, it’s fine for editing spreadsheets or probably watching the news at night on a TV. Not the best idea when grading videos or watching something when you care about accuracy.

There also those to whom crushed blacks look cool. When I first got into color grading about 10 years ago, I was guilty of crushing blacks to make the image pop more at the expense of shadow detail. Every online tutorial showed you how to do it. So, if you want to get into director intent, I’d say that not every director always knows what they are doing.

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Thanks GeorgeAB and ScenicLabs - I am slowly getting used to a not totally dark room when using bias lighting. Perception & Preference is important and I do like the deeper blacks bias lighting gives.

Only problem now is that I really like the look of the setup when the MediaLight strip is at 100% - looks very cool

Ok, I will desist
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post #18 of 26 Old 02-06-2020, 11:19 PM
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So, if you want to get into director intent, I’d say that not every director always knows what they are doing.
Aye, how do any of us know what the directors intent is without access to the mastering monitor used ...... ultimately one can only calibrate to standards and that's it.

As for Black levels, My QLED has deep blacks - but I am pretty sure there is some local dimming black crush. The only way I can compare as a consumer is to compare with an OLED (like Gravity scene).
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post #19 of 26 Old 02-07-2020, 10:32 AM
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Yeah, and some would argue that you should look at the peak luminance used for mastering HDR content to determine the 10% level.

That seems like a lot of extra work considering that the SMPTE standard is a fixed 4.5 nits.

From SMPTE ST 2080-3:2017 Reference Viewing Environment for Evaluation of HDTV Images (A SMPTE reference standard, not a recommendation )

"There is consensus in the industry that 10 nits is too high, as evidenced by the fact that this level is rarely if ever used. Research has revealed that surround levels below 2 nits have minimal effect on the perception of black. This implies that a suitable surround level will be somewhere below 10 nits but not lower than 2 nits. The geometric mean of these two values is 4.5 nits, so a value close to this would seem to be a reasonable compromise."

I will be a rebel and disagree slightly here. There are situations where as high as 15% have been used as an upper level (usually non-OLED), and when I talked with Joel Silver about this when we went through manufacturer certification, he agreed that ISF still recommends 10-15%. I think this might be because a lot of pros are using OLEDs and I see a lot of consumers with LED. Also pros tend to be more protective of their darkness adaptation. We're working on a desk lamp with GeorgeAB (a joint MediaLight/Ideal-Lume product) and are taking great care to avoid any direct light to the colorists' eyes. There was a dimmer button that was rejected because it was too shiny.

Again, SMPTE is largely in the pro world and ISF is focused on consumer experience. Some pro monitors cost $40K+ for a 32" display. That's a lot of lattes! You'd expect the contrast ratio and peak luminance to be pretty ok.



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Aye, how do any of us know what the directors intent is without access to the mastering monitor used ...... ultimately one can only calibrate to standards and that's it.

As for Black levels, My QLED has deep blacks - but I am pretty sure there is some local dimming black crush. The only way I can compare as a consumer is to compare with an OLED (like Gravity scene).

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Publisher of Spears & Munsil Benchmark UHD HDR Benchmark.
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post #20 of 26 Old 02-07-2020, 11:52 AM
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Originally Posted by Scenic Labs View Post
Yeah, and some would argue that you should look at the peak luminance used for mastering HDR content to determine the 10% level.

That seems like a lot of extra work considering that the SMPTE standard is a fixed 4.5 nits.

From SMPTE ST 2080-3:2017 Reference Viewing Environment for Evaluation of HDTV Images (A SMPTE reference standard, not a recommendation )

"There is consensus in the industry that 10 nits is too high, as evidenced by the fact that this level is rarely if ever used. Research has revealed that surround levels below 2 nits have minimal effect on the perception of black. This implies that a suitable surround level will be somewhere below 10 nits but not lower than 2 nits. The geometric mean of these two values is 4.5 nits, so a value close to this would seem to be a reasonable compromise."

I will be a rebel and disagree slightly here. There are situations where as high as 15% have been used as an upper level (usually non-OLED), and when I talked with Joel Silver about this when we went through manufacturer certification, he agreed that ISF still recommends 10-15%. I think this might be because a lot of pros are using OLEDs and I see a lot of consumers with LED. Also pros tend to be more protective of their darkness adaptation. We're working on a desk lamp with GeorgeAB (a joint MediaLight/Ideal-Lume product) and are taking great care to avoid any direct light to the colorists' eyes. There was a dimmer button that was rejected because it was too shiny.

Again, SMPTE is largely in the pro world and ISF is focused on consumer experience. Some pro monitors cost $40K+ for a 32" display. That's a lot of lattes! You'd expect the contrast ratio and peak luminance to be pretty ok.
To clarify what the SMPTE standard document states, the official standard is 5 nits, +/- 0.5.



"6.4 Surround Luminance Value


The reflected light from the surround or background in the field of view shall have a luminance of 5.0 ± 0.5 candelas per square meter....." SMPTE ST 2080-3:2017



The 4.5 nits quote is a point of discussion on background, and at one extreme of the specified tolerances. I suspect one reason the lower ambient light level is preferred for mastering programs is due to the fact that roughly half the time static images are being evaluated rather than full motion images. Full motion video typically subjects the viewer to erratic fluctuations in scene brightness over time, similar to watching a strobe light or driving into oncoming traffic at night, which is more fatiguing. The ISF is not a formal video industry standards body, but a consulting and certifying firm (similar to THX and more recently the PVA) that teaches, advocates, and interprets formal standards and recommended practices published by the likes of SMPTE, ITU, EBU, IEEE, ISO, ANSI, etc.
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post #21 of 26 Old 02-07-2020, 12:07 PM
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I don't disagree at all, and some modes like ISF Sport diverge further from the standard, but do so so that you can watch a game with friends and see your beer. That's partly what got us into making dimmable D65 bulbs for downlighting. I think that what they have to say adds to the conversation since they calibrate so many displays in the real world.

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To clarify what the SMPTE standard document states, the official standard is 5 nits, +/- 0.5.



"6.4 Surround Luminance Value


The reflected light from the surround or background in the field of view shall have a luminance of 5.0 ± 0.5 candelas per square meter....." SMPTE ST 2080-3:2017



The 4.5 nits quote is a point of discussion on background, and at one extreme of the specified tolerances. I suspect one reason the lower ambient light level is preferred for mastering programs is due to the fact that roughly half the time static images are being evaluated rather than full motion images. Full motion video typically subjects the viewer to erratic fluctuations in scene brightness over time, similar to watching a strobe light or driving into oncoming traffic at night, which is more fatiguing. The ISF is not a formal video industry standards body, but a consulting and certifying firm (similar to THX and more recently the PVA) that teaches, advocates, and interprets formal standards and recommended practices published by the likes of SMPTE, ITU, EBU, IEEE, ISO, ANSI, etc.
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post #22 of 26 Old 02-07-2020, 01:44 PM
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post #23 of 26 Old 02-08-2020, 11:58 AM
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Ok, so 10% it is (and go lower if too bright). This equates to ~18 nits on my QLED which is calibrated to ~180 nits (SDR). Thank you gents.

I have my MediaLight set to ~20% to match the S&M UHD Benchmark Disk Bias Light Pattern (SDR). However, the MediaLight YouTube pattern is much brighter than the S&M or any other 10% pattern I throw up. I have to set the MedialLight to almost 80% to match.

Which one is the correct reference pattern please?

PS I am getting used to having bias lighting in a dark room environment - prefer it to a totally dark room now

NB The S&M HDR Bias Light pattern looks way too dim - can barely see it so ignoring.

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post #24 of 26 Old 02-09-2020, 04:36 AM
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Anyway, so I got my meter out and set the % of the MediaLight by measuring the reflection off the wall. Set it to 18 nits (10% of 180 nits) which is 68-70 % setting on the remote.

Out of interest, I then measured the S&M bias pattern and that is set to 5 nits as per the SMPTE standard so explains the difference I noted above with the MedialLight pattern aiming for 10%.

Edit : Just re-read ScenicLabs & GeorgeAB posts and 18 nits is too high. So have set to 15 nits (60% on remote) for now and will experiment with 10 nits (40%). In other words, should not be a straight 10% of the peak SDR luminance but in the range of 5 to 15%.
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post #25 of 26 Old 02-18-2020, 10:31 AM
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I have my OLED calibrated to reference and I'm using the Medialight system paired with the S&M UHD test disk.

I used the bias light test pattern to visually match the rear wall which is a "antique tin" color and I adjusted the bias light with the precise controls until I got a perceptual "blend" with the pattern and the back wall.

This turned out to be actually a pretty low setting, compared to the 10% IRE I was running before, and combined with an OLED, I think it works perfectly. I don't feel the need to be in a pitch black room, nor am I distracted by any reflected light coming from the bias light.

The TRUE answer though? I keep the medialight plugged into the USB, and ON at all times, even during the day. Why? Because it turns on and off with the LG OLED and when it turns off, I know when the TV completed a compensation cycle and I can turn back on again. Haha.

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post #26 of 26 Old 02-18-2020, 07:27 PM
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I have settled for 8 nits against a white wall background. Mostly I prefer the setup to a completely dark room but there are times I kinda prefer the dark room picture and switch the light off - depends on what I am watching. Will take some time to fully switch.
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