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I can't seem to find this information anywhere as I'm not a SMPTE member.


sRGB is clearly 80 nits, but when people talk about display calibration, they throw around numbers like 120 nits.


What should it be?
 

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Quote:
Originally Posted by ChuckZ /forum/post/18106224


I can't seem to find this information anywhere as I'm not a SMPTE member.


sRGB is clearly 80 nits, but when people talk about display calibration, they throw around numbers like 120 nits.


What should it be?

Do you mean the peak luminance output?


My advice is to ignore it and set your display as high as it will go without clipping or run-out in any channels.
 

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Discussion Starter · #3 ·
Yes, peak luminance is more appropriately phrased.


I know in the real world, you can set your display as high as it will go before it clips. However, in a theoretical situation, where you television can become infinitely bright, you'd have to level off the peak luminance at some point because your eyes couldn't discern such a high simultaneous contrast. Therefore, doesn't the Rec. 709 specification account for this in some way?
 

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Rec709 doesn't define a reference luminance or a reference viewing environment. There are some other specs which describe this in various ways which I am less familiar with.


How bright you want depends on the size of the screen, ambient lighting, backlighting, and viewer preference. Most of the recommendations around here are more about pleasing ranges that are commonly targeted, which are rather arbitrary but which fit well within a particular viewing environment.


I mean, just ballpark on something like a plasma, I might target a range of 20-40 foot lamberts depending on lighting conditions and the type of content the viewer is most concerned about (brighter for sports & TV, dimmer for mainly movies for instance). That would be ~70 to ~140 nits, roughly. I would target probably 10 to 20 footlamberts for a large projection screen in a darkish or dark room, again depending.


That's just my viewing preference, I think those are reasonable value ranges, but I'm sure others will chime in as well.


I don't recall the SMPTE specs that describe in more detail the studio environment, but it's important to note that as most of our viewing environments deviate from that type of viewing environment and screen size, we have to make some intelligent derivations based on that standard which lead to different but appropriate conclusions that match how our particular viewing environment differs.
 

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Rec709 is essentially entirely concerned with scanning standards, signals, etc. It's not concerned as much(or really at all) with the studio environment, the display, etc. That's where SMPE standards come in, and I believe there are also some other ITU standards that provide some guidance there. I don't have any of those, I believe I have one ITU standard regarding comparing high-definition video quality, which isn't really what we're talking about exactly, but it gives some desired traits about the viewing environment lighting, lighting lcoation, etc, and peak luminance of the screen of 150-250 cd/m2
 

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Quote:
Originally Posted by ChuckZ /forum/post/18106354


Would you mind uploading that? Or is it unable to be distributed?

I have a hard copy, and can't find a version online. I know I did get it online at some point, but I don't know if it is still out there on the net.


It is, specifically, ITU-R BT.710-4 "Subjective Assessment Methods for Image Quality in High-Definition Television."


You might have better luck searching. And as I said, I believe there are some more relevant SMPTE documents on the subject, I was hoping others would chime in.
 

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Quote:
Originally Posted by ChuckZ /forum/post/18106354


Would you mind uploading that? Or is it unable to be distributed?

These are not free:

SMPTE RP 166: 'Critical Viewing Conditions For Evaluation Of Color Television Pictures'

SMPTE RP 167: 'Alignment Of NTSC Color Picture Monitors'


THX promulgates best practice for theatres and their recommendations are often co-opted by HT folks.
 

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Poynton claims that the standard for studio reference display luminance is 80 cd/m2 (23 fL) for EBU and 120 cd/m2 (35 fL) for SMPTE on p. 24 of this document

http://www.poynton.com/notes/PU-PR-I...n-PU-PR-IS.pdf


However, I don't know specifically which SMPTE standard he refers to.


The DCI standard for cinema luminance is 48 cd/m2 (14 fL).
 

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Originally Posted by TomHuffman /forum/post/18109633


However, I don't know specifically which SMPTE standard he refers to.

That would be RP166. At 100% stimulus (they say 100IRE) a reference white field should have the chromaticity of D65 and an aim luminance of 120cd/m2 or 35fL.
 

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Quote:
Originally Posted by TomHuffman /forum/post/18109633


Poynton claims that the standard for studio reference display luminance is 80 cd/m2 (23 fL) for EBU and 120 cd/m2 (35 fL) for SMPTE on p. 24 of this document

http://www.poynton.com/notes/PU-PR-I...n-PU-PR-IS.pdf


However, I don't know specifically which SMPTE standard he refers to.


The DCI standard for cinema luminance is 48 cd/m2 (14 fL).

Is there an assumption about the display size and viewing distance for the "studio" setting? I would think the approapriate luminance level should be a function of those two.
 

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Originally Posted by mmoh00 /forum/post/18111328


Is there an assumption about the display size and viewing distance for the "studio" setting?

Yes, distance is 5 times screen height. At the time I suspect there was not much variance in grading bay BVM size. There was probably greater variance in luminance -- anywhere from 80-120 seems to be common.


These specs are not for consumer use although they've been widely adopted by some enthusiasts. They are for color grading and similar tasks.
 

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Quote:
Originally Posted by bodosom /forum/post/18112266


Yes, distance is 5 times screen height. At the time I suspect there was not much variance in grading bay BVM size. There was probably greater variance in luminance -- anywhere from 80-120 seems to be common.


These specs are not for consumer use although they've been widely adopted by some enthusiasts. They are for color grading and similar tasks.

Thanks for the info! BTW, what's BVM?


EDIT: I think I found the answer. BVM = Broadcast Video Monitor: a CRT?
 

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Quote:
Originally Posted by ChuckZ /forum/post/18113250


The Sony BVM model line was THE de facto CRT reference monitor that Hollywood used.

Actually I'd say it was the sony FW900 monitor you'd find in the majority of digital film grading situations.


The big(ish) BVMs were only really used to keep the client happy. For critical color decisions they'd usually nip over to the FW900 as it was usually lutted and kept up to date.
 

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Discussion Starter · #18 ·

Quote:
Originally Posted by Mr.D /forum/post/18113592


Actually I'd say it was the sony FW900 monitor you'd find in the majority of digital film grading situations.


The big(ish) BVMs were only really used to keep the client happy. For critical color decisions they'd usually nip over to the FW900 as it was usually lutted and kept up to date.

Thanks for the correction.


I've actually tried really hard to find old Sony Trinitron CRTs. Do you know where to find them?


Some people have told me to forgo the baggage of CRTs in favor of LCDs like geometry and weight. However, black levels and uneven backlighting levels still really bother me when it comes to LCDs.
 

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Quote:
Originally Posted by mmoh00 /forum/post/18112687


Thanks for the info! BTW, what's BVM?


EDIT: I think I found the answer. BVM = Broadcast Video Monitor: a CRT?

Well I was speaking generically about a studio monitor rather than the classic Sony BVM CRT.


The Sony BVM product line is now LCD based and I've heard that in the US Panasonic is infiltrating mastering bays.


Naturally, since I just some random gadget lover, I leave it to folks like Mr.D to speak authoritatively about digital grading.
 

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Quote:
Originally Posted by ChuckZ /forum/post/18113735


Some people have told me to forgo the baggage of CRTs in favor of LCDs like geometry and weight. However, black levels and uneven backlighting levels still really bother me when it comes to LCDs.

If you have the requisite dollars (i.e. BVM CRT dollars) I think you can get quite good LCD based displays.


It's terribly off-topic but perhaps Mr.D can share some thoughts.
 
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