HDR & Gamma - What/How? - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 3Likes
  • 1 Post By hatman5700
  • 2 Post By EvLee
 
Thread Tools
post #1 of 4 Old 12-17-2019, 02:38 PM - Thread Starter
Member
 
hatman5700's Avatar
 
Join Date: May 2013
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 2
HDR & Gamma - What/How?

What's the appropriate way to approach HDR and Gamma?

For SDR most recognize 2.2 as a 'standard' of sorts, and there are a variety of ways to try and achieve this from minimal measuring such as using windows calibration, 'upgrading' to eye tests from lagom.com or other picture calibration testing images, all the way to having a professional calibration done with colorimeters and tools. Ultimately you adjust a gamma setting on your TV, in addition to potentially contrast, brightness, and RGB point values.

What is the equivalent to ANNNNNNNNNNY of what I just listed for HDR?
hatman5700 is offline  
Sponsored Links
Advertisement
 
post #2 of 4 Old 12-17-2019, 02:51 PM - Thread Starter
Member
 
hatman5700's Avatar
 
Join Date: May 2013
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 2
I'll follow-up with some small facts I've surmised on HDR (and Gamma):
  • Gamma is used because the human eye discerns colors differently based on the backgrounds that are present (I know this is an oversimplification and likely had some questionable words, but roll with me here).
  • Historically TVs did not use absolute measurements of light (i.e. nits), so gamma was introduced to be allow for a relative controller based on percentage to allow for calibration of ANY TV, regardless of specification, to have a controllable gamma curve. This allows calibration to a given standard, say 1.8 or 2.2 or 2.4 for ANY TV in existence. TV-#1 may need a 90% gamma introduction to reach a 2.2 standard, TV-#2 may need 95%, TV-#3 may need 105.6%. It's relative.
  • With HDR, there is now an absolute measurement of light (nits). This allows for an exact specification of nits from the content creator, and the TV no longer has to jump through hoops to match the intended light levels from the content creator; so long as it is upholding the HDR standard - it just lights up to the specified nit value to accomplish the true intended picture of whatever is being viewed.
  • HDR10 is specified for 1000nits, and HDR10+ is specified for 4000nits. Most quality TVs can cover the range of 1000nits.

Does this mean you should not touch Gamma AT ALL for 1000 nit TV's viewing content HDR10 content intended for 1000 nits?
Does this mean you need to adjust Gamma for 1000 nit TV's watching HDR10+ content?


Please let me know if I have an issue with any of this, be it a specific misstep or a foundational misunderstanding!
Madmax67 likes this.
hatman5700 is offline  
post #3 of 4 Old 12-18-2019, 10:33 AM - Thread Starter
Member
 
hatman5700's Avatar
 
Join Date: May 2013
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 2
Any good research/areaa for this? Hard to search this topic - not finding hits
hatman5700 is offline  
Sponsored Links
Advertisement
 
post #4 of 4 Old 12-18-2019, 08:55 PM
Advanced Member
 
EvLee's Avatar
 
Join Date: Dec 2009
Posts: 709
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 406 Post(s)
Liked: 419
Quote:
Originally Posted by hatman5700 View Post
Any good research/areaa for this? Hard to search this topic - not finding hits
It's all defined in ITU-R BT.2100. Refer to table 4, Reference PQ EOTF. You can download the document from here: https://www.itu.int/dms_pubrec/itu-r...7-I!!PDF-E.pdf

FWIW, HDR10 is not defined to be 1000 nits. That is just a common practice that some releases follow, but HDR10 can actually use any portion of the PQ 10,000 nit range. The "10" in HDR10 specifically refers to 10-bit encoding. HDR10+ can also be any range of nits, the "+" just indicates that it also uses the dynamic metadata format that was created by Samsung.
Madmax67 and CAVX like this.
EvLee is offline  
Sponsored Links
Advertisement
 
Reply High Dynamic Range (HDR) & Wide Color Gamut (WCG)

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off