Video Calibration Q&A - Page 6 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #51 of 77 Old 01-06-10, 08:15 AM Thread Starter
Shackster
Bill
 
Join Date: Jul 2006
Location: Inner Loop, Houston, T
Posts: 44
Re: Video Calibration Q&A

Quote:
glaufman wrote: View Post
And here I thought all along that at least the movie studios stuck to the 0.45 encode... at least from what's "seen" on the monitor to the signal...
By and large they do, though you can't put too much of a universal law around this (the SMPTE and ITU standards are very clear). A lot of that is hard-coded into the capture devices themselves. Then, if the tech working on the production flow changes it, then it is probably intentional. Decode gamma is all over the map.

CalMAN -- Home Theater Calibration Software
Bear5K is offline  
Sponsored Links
Advertisement
 
post #52 of 77 Old 01-06-10, 09:36 AM
Elite Shackster
 
glaufman's Avatar
Greg
 
Join Date: Nov 2007
Location: NY
Posts: 2,601
Re: Video Calibration Q&A

Quote:
Bear5K wrote: View Post
Then, if the tech working on the production flow changes it, then it is probably intentional.
Yes, they're free to "bake in" anything they want... sometimes I wonder if we couldn't make a distinction between what we call "gamma" for the encode/decode chain vs. "gamma" of a particular image...

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline  
post #53 of 77 Old 01-06-10, 09:43 AM Thread Starter
Shackster
Bill
 
Join Date: Jul 2006
Location: Inner Loop, Houston, T
Posts: 44
Re: Video Calibration Q&A

Quote:
glaufman wrote: View Post
Yes, they're free to "bake in" anything they want... sometimes I wonder if we couldn't make a distinction between what we call "gamma" for the encode/decode chain vs. "gamma" of a particular image...
You may be over-thinking the issue. When someone pushes the gamma on a scene intentionally, it is to create a particular look. If you correct for that push, then you lose rendering intent. What "ought" to happen is concrete guidelines that tie reproduction environment to recommended gamma in a way that accounts for the "desired" home environment (there are very strict/rigid guidelines for grading studios) so we can preserve rendering intent across heterogeneous environments.

CalMAN -- Home Theater Calibration Software
Bear5K is offline  
 
post #54 of 77 Old 01-06-10, 09:48 AM
Elite Shackster
 
glaufman's Avatar
Greg
 
Join Date: Nov 2007
Location: NY
Posts: 2,601
Re: Video Calibration Q&A

I very often over think issues... it's what I do...
But I think I'm OK on this one... I don't want to correct for any indended push... what I'm talking about is strictly language/usage to avoid what I see as some confusion among some of us less edumacated folks...

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline  
post #55 of 77 Old 01-06-10, 09:55 AM Thread Starter
Shackster
Bill
 
Join Date: Jul 2006
Location: Inner Loop, Houston, T
Posts: 44
Re: Video Calibration Q&A

Quote:
glaufman wrote: View Post
I very often over think issues... it's what I do...
But I think I'm OK on this one... I don't want to correct for any indended push... what I'm talking about is strictly language/usage to avoid what I see as some confusion among some of us less edumacated folks...
All that the "average" enthusiast who cares about calibration and preserving rendering intent (which already puts you way, way above average) needs to know is that he or she needs to start with a 2.5 average gamma and adjust it downward to correct for ambient light. You then also need to potentially tweak specific parts of the gamma curve for display-specific limitations (and a bit of taste/content preference).

For most people with non-dedicated environments, something between a 2.0 and a 2.3 works, depending upon the specifics. In a bat cave, you can make a 2.5 work well.

CalMAN -- Home Theater Calibration Software
Bear5K is offline  
post #56 of 77 Old 01-06-10, 05:42 PM
Elite Shackster
 
glaufman's Avatar
Greg
 
Join Date: Nov 2007
Location: NY
Posts: 2,601
Re: Video Calibration Q&A

Quote:
Bear5K wrote: View Post
(which already puts you way, way above average)
Awhhh!
OK, granted the average guy doesn't need to be specific about language, but I've seen so much confusion between so-called experts (albeit not on this forum) when one's talking about encode, one's talking decode, one's talking about rendering... but I digress as usual...
Quote:
You then also need to potentially tweak specific parts of the gamma curve for display-specific limitations (and a bit of taste/content preference).
I'm under the impression that without an outboard processor, this really can't be done, right? What displays have this resolution on their gamma adjustments, even in the service menus? Is there some way to adjust gamma I'm missing?

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline  
post #57 of 77 Old 02-15-10, 07:52 PM
Elite Shackster
 
glaufman's Avatar
Greg
 
Join Date: Nov 2007
Location: NY
Posts: 2,601
Re: Video Calibration Q&A

OK... I've given you guys a break for a while... time for another one... yes, that means I've been thinking again... (sorry about that...)...
CCFL backlights experience a color shift if they're set too bright, yes? Do LED edgelights do the same thing? How about backlights if you're left local dimming off? Local dimming on?
Assuming you've turned off all CE dimming...
Would you ever turn the backlight down to achieve a better D65? OF course, you still have your normal cuts/gains...

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline  
post #58 of 77 Old 04-12-10, 08:10 AM Thread Starter
Shackster
Bill
 
Join Date: Jul 2006
Location: Inner Loop, Houston, T
Posts: 44
Re: Video Calibration Q&A

Quote:
glaufman wrote: View Post
I'm under the impression that without an outboard processor, this really can't be done, right? What displays have this resolution on their gamma adjustments, even in the service menus? Is there some way to adjust gamma I'm missing?
My RS10 and Pioneer Kuro both have the ability to select different gamma curves. I believe that the Kuro can adjust its gamma curve at a more granular level with the ISF controls turned on (I've never bothered with mine since it is the "daily driver" TV). In general, though, yes, you will need an external processor for most of this.

Quote:
glaufman wrote: View Post
OK... I've given you guys a break for a while... time for another one... yes, that means I've been thinking again... (sorry about that...)...
CCFL backlights experience a color shift if they're set too bright, yes? Do LED edgelights do the same thing? How about backlights if you're left local dimming off? Local dimming on?
Assuming you've turned off all CE dimming...
Would you ever turn the backlight down to achieve a better D65? OF course, you still have your normal cuts/gains...
Sorry I missed this one from a while back. To the best of my knowledge, LEDs do not color shift. The biggest "hit" on them is the relatively "spiky" (i.e., narrow) frequency range at which they operate, making some measurement instruments less useful in measuring performance. In order to measure them successfully, you need a spectroradiometer with a sufficiently narrow measurement interval or a colorimeter that has specifically been calibrated for use with LEDs.

As for CCFLs, I cannot attest to what happens in a lab, but my experience in the field where I've seen color shifting from an LCD panel seems more of an issue with the LCD side of the panel, rather than the backlight.

Net answer: use the backlight control to get the white point close to where you want your maximum luminance (i.e., not torch mode unless you have really specific reasons/issues). If the backlight control measurably affects grayscale, see if you can return the panel and get a different one.

CalMAN -- Home Theater Calibration Software

Last edited by Bear5K; 04-12-10 at 08:15 AM.
Bear5K is offline  
post #59 of 77 Old 04-12-10, 09:03 AM
Elite Shackster
 
glaufman's Avatar
Greg
 
Join Date: Nov 2007
Location: NY
Posts: 2,601
Re: Video Calibration Q&A

Quote:
Bear5K wrote: View Post
Sorry I missed this one from a while back.
No worries!
Quote:
or a colorimeter that has specifically been calibrated for use with LEDs.
This one has always perplexed me a little... different displays presumably have a choice of what LEDs they use, as such, how does a single profile matrix make a colorimeter accurate enough across the range of possibilities?
Quote:
Net answer: use the backlight control to get the white point close to where you want your maximum luminance (i.e., not torch mode unless you have really specific reasons/issues). If the backlight control measurably affects grayscale, see if you can return the panel and get a different one.
OkeeDokey!

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline  
post #60 of 77 Old 04-12-10, 12:16 PM Thread Starter
Shackster
Bill
 
Join Date: Jul 2006
Location: Inner Loop, Houston, T
Posts: 44
Re: Video Calibration Q&A

Quote:
glaufman wrote: View Post
This one has always perplexed me a little... different displays presumably have a choice of what LEDs they use, as such, how does a single profile matrix make a colorimeter accurate enough across the range of possibilities?
It gets somewhat complicated, but the issue has to do with tolerances. In other words, a company/manufacturer can calibrate the meter to a particular combination of LEDs, but the accuracy will diminish as you move away from that spec. The upside is that LEDs are actually, in many respects, a more homogeneous lighting technology than what has been used in the past. They still have unit-to-unit variation and manufacturer (of the LEDs and spec) variation, but you don't get as much batch-to-batch variation as you did with things like phosphor (CRT, Plasma, and to an extend CCFL). So, you essentially get a calibration that is more accurate for the technology than using something not dedicated to the technology, but you suffer from wider variances in what manufacturers might put into the display, if that makes sense. Since there are very few manufacturers out there making the necessary blue and "white" LEDs, that tends to constrain the space of what an OEM might actually put into the TV.

Net-net: figure out what the reference display is, and then know that as you drift beyond that manufacturing "group" (e.g., Samsung/Sony/JVC), you might get increased error, but not necessarily enough to invalidate the calibration (LEDs are tough, but doable). To be really sure about things, that's where the $$$ meters come into play, or contracting for a specific calibration for the meter.

CalMAN -- Home Theater Calibration Software
Bear5K is offline  
Reply

Bookmarks

Tags
calibration , qanda , video

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in










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



Posting Rules  
You may post new threads
You may 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 is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome