Forum Jump: 
 2Likes
  • 2 Post By Gregg Loewen
 
Thread Tools
post #1 of 5 Old 01-01-2019, 07:30 AM - Thread Starter
Newbie
 
Join Date: Nov 2018
Posts: 1
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
Wouldn't Following THX Calibration Clip Black and Lose Detail in Dark Scenes?

Wouldn't decreasing black level to the point where the background isn't distinguishable from the shadow around the letters THX in the middle of the screen be the same thing as increasing the white level to the point where subtle shades of white are clipped? Is THX basicly telling us to clip black and lose detail in dark scenes, yet keep detail in bright scenes? While I agree with their instructions for setting contrast, I disagree with their instructions for setting brightness, and I think the shadow around the THX letters in the middle of the screen should be as dark as the display can show them, and decreasing the black level beyond that would clip black in the same way increasing white level too much would clip white.
Chris Kelly is offline  
Sponsored Links
Advertisement
 
post #2 of 5 Old 01-01-2019, 09:16 AM
Advanced Member
 
Gregg Loewen's Avatar
 
Join Date: Feb 2002
Location: New England
Posts: 871
Mentioned: 8 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Liked: 97
it doesnt work like that.
Video follows rules.
in an 8 bit system, you should not be seeing any information below step 16.
DroptheRemote and GeorgeAB like this.

Founder, Professional Video Alliance
Gregg Loewen is offline  
post #3 of 5 Old 01-03-2019, 11:31 AM
AVS Forum Special Member
 
sotti's Avatar
 
Join Date: Aug 2004
Location: Seattle, WA
Posts: 7,044
Mentioned: 7 Post(s)
Tagged: 1 Thread(s)
Quoted: 339 Post(s)
Liked: 342
Quote:
Originally Posted by Chris Kelly View Post
Wouldn't decreasing black level to the point where the background isn't distinguishable from the shadow around the letters THX in the middle of the screen be the same thing as increasing the white level to the point where subtle shades of white are clipped? Is THX basicly telling us to clip black and lose detail in dark scenes, yet keep detail in bright scenes? While I agree with their instructions for setting contrast, I disagree with their instructions for setting brightness, and I think the shadow around the THX letters in the middle of the screen should be as dark as the display can show them, and decreasing the black level beyond that would clip black in the same way increasing white level too much would clip white.
It has to do with the colors used in that logo pattern. It's not actually a logo with a shadow, it's a test pattern that has video black: 8bit code 16 (used for the surround), A dark grey color guessing about 8bit code 48 (used for the lettering), and then a color that is smallest input signal 8bit code 1 (used for the shadow). Since all video depends on black being the minimum light the TV outputs, you want the brightness from the shadow bit 1 to match the actual black level bit 16. So you aren't losing detail since all signal should be above 16, but also colors will look more washed out if you set your brightness to high, as you'll be adding a little bit of dark grey to all the colors.
sotti is offline  
Sponsored Links
Advertisement
 
post #4 of 5 Old 01-04-2019, 07:03 AM
AVS Forum Special Member
 
ConnecTEDDD's Avatar
 
Join Date: Sep 2010
Location: Athens, Greece
Posts: 7,387
Mentioned: 154 Post(s)
Tagged: 1 Thread(s)
Quoted: 2690 Post(s)
Liked: 3270


There are the digital values for video levels of the Brightness Pattern of THX.

It's very basic pattern which can provide a wrong adjustment because of limited bars near 16 (reference black).

-1.8% (12)
0% (16)
2% (20)
3.7% (24)
4% (25)
5.5% (28)
7.3% (32)
9% (36)
11% (40)
13% (44)
14.6% (48)

It can happen the user to do many mistakes using this pattern, for example, the lower value from reference black (16) is the 12 (-1.8%) so the user can increase his black level without realized it because there no 15 bar to use as reference, to see if he has raised his reference black.

Also it can provide clip or wrong adjustment of near black detail since the first digital level above reference black (16) is the 2% Gray (20), ideally you need 17 (0.5% Gray) to have as reference to see what is happening to your near black.

It will provide you better adjustment if you will use the 'basic' Brightness pattern available at the free version of my calibration disk, you can download from my signature, or download the free AVSHD if you like.



If you have a meter, see a trick to the picture with the red circle at this link: http://01900888.com/forum/139-d...l#post56738984

Ted's LightSpace CMS Calibration Disk Free Version for Free Calibration Software: LightSpace DPS / CalMAN ColorChecker / HCFR
S/W: LightSpace CMS, SpaceMan ICC, SpaceMatch DCM, CalMAN 5, CalMAN RGB, ChromaPure, ControlCAL
V/P: eeColor 3D LUT Box - P/G: DVDO AVLab TPG
Meters: JETI Specbos 1211, Klein K-10A, i1PRO2, i1PRO, SpectraCAL C6, i1D3, C5
ConnecTEDDD is online now  
post #5 of 5 Old 01-04-2019, 03:34 PM
AVS Forum Special Member
 
ConnecTEDDD's Avatar
 
Join Date: Sep 2010
Location: Athens, Greece
Posts: 7,387
Mentioned: 154 Post(s)
Tagged: 1 Thread(s)
Quoted: 2690 Post(s)
Liked: 3270
Also be sure that you are not using the Brightness Pattern of Terminator Skynet Edition Blu-Ray.... it has incorrect levels.

If you try to set your brightness level with this pattern you will receive a picture without shadow detail & all information above black will disappear, huge black clipping.

Avoid Completely that Terminator Skynet Edition Disk for Setting Brightness and probably any other disk that include that THX Optimizer chapters (Pixar DVD etc)... T2's has upscalled versions of THX Optimizer DVD patterns version.

THX Calibrator Blu-Ray Disc is accurate.

Ted's LightSpace CMS Calibration Disk Free Version for Free Calibration Software: LightSpace DPS / CalMAN ColorChecker / HCFR
S/W: LightSpace CMS, SpaceMan ICC, SpaceMatch DCM, CalMAN 5, CalMAN RGB, ChromaPure, ControlCAL
V/P: eeColor 3D LUT Box - P/G: DVDO AVLab TPG
Meters: JETI Specbos 1211, Klein K-10A, i1PRO2, i1PRO, SpectraCAL C6, i1D3, C5
ConnecTEDDD is online now  
Sponsored Links
Advertisement
 
Reply Display Calibration



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