Calculating % difference in Y readings between a target point gamma value and actual point gamma value - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 13 Old 06-12-2012, 10:04 PM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
Like the title suggests, is there an easy way to convert point gamma differences into % changes in Y? For example, if I was targeting 2.2 gamma at 10% gray and the actual value ended being 2.25, what would be the % difference in Y between the two?

Is there a spreadsheet or other simple tool available to make such calculations/comparisons? I asking for both power and BT.1886 formulas.
PlasmaPZ80U is offline  
Sponsored Links
Advertisement
 
post #2 of 13 Old 06-12-2012, 10:06 PM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
perhaps something on the lines of this: http://www.chromapure.com/colorscience-gamma.asp

206
PlasmaPZ80U is offline  
post #3 of 13 Old 06-13-2012, 10:22 AM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
PlasmaPZ80U is offline  
post #4 of 13 Old 06-13-2012, 10:31 AM
AVS Special Member
 
sotti's Avatar
 
Join Date: Aug 2004
Location: Seattle, WA
Posts: 6,585
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Liked: 164
Quote:
Originally Posted by PlasmaPZ80U View Post

is this correct? Point Gamma Converted Into Luminance Changes.xls 29k .xls file

Yes it is.

Joel Barsotti
SpectraCal
CalMAN Lead Developer
sotti is offline  
post #5 of 13 Old 06-13-2012, 10:41 AM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
Quote:
Originally Posted by sotti View Post

Yes it is.

great, now I can easily calculate the difference between one point gamma value versus another, at each level of stimulus

if I was to introduce black level compensation into the mix, how would I do that?
PlasmaPZ80U is offline  
post #6 of 13 Old 06-13-2012, 11:01 AM
AVS Special Member
 
sotti's Avatar
 
Join Date: Aug 2004
Location: Seattle, WA
Posts: 6,585
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 12 Post(s)
Liked: 164
Quote:
Originally Posted by PlasmaPZ80U View Post

great, now I can easily calculate the difference between one point gamma value versus another, at each level of stimulus
if I was to introduce black level compensation into the mix, how would I do that?

I wouldn't worry about that too much, it basically changes the exponent targets for the stimulus, the difference between the exponents are still consistent.

Joel Barsotti
SpectraCal
CalMAN Lead Developer
sotti is offline  
post #7 of 13 Old 06-13-2012, 12:25 PM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
Quote:
Originally Posted by sotti View Post

I wouldn't worry about that too much, it basically changes the exponent targets for the stimulus, the difference between the exponents are still consistent.

ok, thanks
PlasmaPZ80U is offline  
post #8 of 13 Old 06-13-2012, 06:01 PM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
what the is smallest % difference in luminance that would be visible? Also, what is the largest % difference in luminance that would be acceptable?
PlasmaPZ80U is offline  
post #9 of 13 Old 06-14-2012, 04:58 AM
Member
 
Monitorman's Avatar
 
Join Date: Feb 2001
Location: New York, NY
Posts: 194
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 14
Quote:
Originally Posted by PlasmaPZ80U View Post

what the is smallest % difference in luminance that would be visible? Also, what is the largest % difference in luminance that would be acceptable?

Hi PlasmaPZ80U,

I am not positive about the % of error in color luminance that would actually be visible, but the delta error we strive for is below 3%. I would guess that anything above 5% would begin to be visible to a trained eye at least. I can tell you that low luminance is more visibly disturbing to me than luminance levels that are too high, particularly with green. Hope that helps.

Kevin Miller
ISF Technician
Co-Instructor ISF Level I & II Seminars
Display Product Development Consultant
kevin@isftv.com
Co-founder tweaktv.com
Monitorman is offline  
post #10 of 13 Old 06-14-2012, 09:00 AM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
Quote:
Originally Posted by Monitorman View Post

Hi PlasmaPZ80U,
I am not positive about the % of error in color luminance that would actually be visible, but the delta error we strive for is below 3%. I would guess that anything above 5% would begin to be visible to a trained eye at least. I can tell you that low luminance is more visibly disturbing to me than luminance levels that are too high, particularly with green. Hope that helps.

Sorry, I forgot to clarify. I was referring to gamma differences specifically (represented as % luminance error from target value).
PlasmaPZ80U is offline  
post #11 of 13 Old 06-14-2012, 03:15 PM
AVS Special Member
 
TomHuffman's Avatar
 
Join Date: Jan 2003
Location: Springfield, MO
Posts: 6,358
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 204
The simplest way to answer this is to just convert reference and test xyY colors to Lab, vary the Y value only and then see how much the dE changes. I'd use CIE94 for this.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

TomHuffman is offline  
post #12 of 13 Old 06-14-2012, 03:34 PM - Thread Starter
AVS Special Member
 
PlasmaPZ80U's Avatar
 
Join Date: Feb 2009
Posts: 7,055
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 11 Post(s)
Liked: 187
Quote:
Originally Posted by TomHuffman View Post

The simplest way to answer this is to just convert reference and test xyY colors to Lab, vary the Y value only and then see how much the dE changes. I'd use CIE94 for this.

is the first spreadsheet on this page the correct one to do this with?
PlasmaPZ80U is offline  
post #13 of 13 Old 06-14-2012, 08:07 PM
AVS Special Member
 
TomHuffman's Avatar
 
Join Date: Jan 2003
Location: Springfield, MO
Posts: 6,358
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 204
Yes. I just uploaded an edited version that adds custom color calculation.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

TomHuffman is offline  
Reply Display Calibration

User Tag List

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