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# GrayScale Calibration

Question, when you go to calibrate your grayscale you should start with the two point and adjust using the white balance gains and offsets. Now I know some people use 80% for the gains and others use 100%. Now if I use 100% and let's say my red is at 120% my blue is at 110% and my green is down at 85%, how should I go about adjusting this? Should I leave green alone and bring the red and blue down to balance all three or do I bring green up some and then bring red and blue down to balance them. I guess my real question is when do you touch green? I know that I can bring red and blue down and get them all to balance and this will give me a certain Y value. Or I can bring green up and then balance all three and this will give me a different Y value. Now please correct me if I am wrong here but isn't the Y value at 100% the base for all the rest, like at 50 or 60%? I do know that when you make changes to 100 and the Y value changes it changes all the other points. I guess this goes back to if 100 is the base for the rest and I can obtain different Y values depending on how I adjust red, green and blue what is the standard or the proper way to adjust these. I hope I am making sense here.
Thanks

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Quote:
Originally Posted by KTM250

Question, when you go to calibrate your grayscale you should start with the two point and adjust using the white balance gains and offsets. Now I know some people use 80% for the gains and others use 100%.

Typically if the set only has 2 point you start with 80/30 get them close, then run the complete scale and make compromise adjustments to get everything as flat as you can.

If you have 10 point which will adjust gamma, you start with a 2 point using the 100/30. I "THINK" it is done this way so you do not inadvertently put a dip or peak in the gamma at 80%. Because as you have said, gamma is a calculated curve that relies on the max 100% Y.

Quote:
Originally Posted by KTM250

Now if I use 100% and let's say my red is at 120% my blue is at 110% and my green is down at 85%, how should I go about adjusting this? Should I leave green alone and bring the red and blue down to balance all three or do I bring green up some and then bring red and blue down to balance them. I guess my real question is when do you touch green?

The way most of the experience folks have explained this to me is that Green is where you get most of the light output. So adjust red and blue to the green and only touch green as a last resort. This was far more important in the CRT days, now we have the back light so not as important. Sometimes the manufacture only gives you cuts on the high end (controls start at 0 and only go down.. So you are safest to follow the don't touch green till last.

Quote:
Originally Posted by KTM250

Now please correct me if I am wrong here but isn't the Y value at 100% the base for all the rest, like at 50 or 60%? I do know that when you make changes to 100 and the Y value changes it changes all the other points. I guess this goes back to if 100 is the base for the rest and I can obtain different Y values depending on how I adjust red, green and blue what is the standard or the proper way to adjust these. I hope I am making sense here.
Thanks

Yes, Gamma is a calculated curve that uses the max 100% and min 0% luminous and the target gamma you have set within the software i.e. 2.2 to make the calculation as to what the Y needs to be at each stimulus.
Quote:
Originally Posted by KTM250

Question, when you go to calibrate your grayscale you should start with the two point and adjust using the white balance gains and offsets. Now I know some people use 80% for the gains and others use 100%. Now if I use 100% and let's say my red is at 120% my blue is at 110% and my green is down at 85%, how should I go about adjusting this? Should I leave green alone and bring the red and blue down to balance all three or do I bring green up some and then bring red and blue down to balance them. I guess my real question is when do you touch green? I know that I can bring red and blue down and get them all to balance and this will give me a certain Y value. Or I can bring green up and then balance all three and this will give me a different Y value. Now please correct me if I am wrong here but isn't the Y value at 100% the base for all the rest, like at 50 or 60%? I do know that when you make changes to 100 and the Y value changes it changes all the other points. I guess this goes back to if 100 is the base for the rest and I can obtain different Y values depending on how I adjust red, green and blue what is the standard or the proper way to adjust these. I hope I am making sense here.
Thanks

What type of Display are you calibrating?
Quote:
Originally Posted by WiFi-Spy

What type of Display are you calibrating?

I have a samsung PN59D8000. Which has the 10pt controls.
Airscapes, you said only touch green as a last resort, so what does that mean?
So if I run out of adjustment with red and blue then use green?
Green is the equivalant to contrast at the high end and brightness contros at the low end. You only touch green if you need to correct gamma at stimuli levels.

So you'd run 2 point, then look at your gamma in addition to grayscale. If the gamma is off at a certain stimuli level, you adjust the green at that stimuli, then readjust red and blue to green. Then take readings again and readjust where necessary.
What dsskid said!

KTM250
I have not calibrated a Samsung yet and don't know what software you are using but with Calman it is rather easy to get gray scale in line and keep Gamma correct with a 10 point adjustment.
You set your single point gray scale chart to absolute so it includes the gamma target you have chosen to set and you do the 10 point from 100% down.
You start with a 100% stimulus pattern and adjust RGB to 0 on the chart (zero being the target spot where it needs to be). Use R&B first then green if you have but you want all 3 at 0
Then go to 90% stimulus and do the same thing. The software makes sure you are keeping gamma in line, continue down to 10%.

Gamma is just a mathematical calculation of how fast the light output increase from 0 to 100% over the 10 steps. A low Gamma number 1.6 mean that there are bigger jumps between each measured stimulus and a high gamma 2.5 means that it is a slower ramp up.

This is all calculated using 0% and 100%. So assuming a 2.2 gamma target set in the software preferences someplace and you are adjust the 10 point RGB balance you are also adjusting how bright the image is at that level or stimulus.
If for instance you don't look at the correct chart or are not looking at the data grid comparing the Target Y to your actual Y and you adjust 60% so RGB is dead even BUT to bright (brighter than the target Y for that stimulus) your gamma curve will dip below the 2.2 target at 60%. The video image between 50% and 60% got brighter than it should so the curve now has a peak in it.

Hope that all makes sense! I had a hard time understanding this at first, but once you get the idea, and see it in action with your software it will be very clear.
Thanks guys for the replys. I believe that I understand most of this, but still have the question of doing the 2PT. So should I use 80 or 100% for the gain adjust. If I use 100 then once again I can use red and blue to balance the three and get a certain Y value or I could bring green up and then balance with red an blue which would give me a different Y value. It seems like there is more then one way to skin a cat here. As far as the 10PT goes I understand how to do that. I guess it goes back to how do I know that 100 is set correctly which is the base for all the rest.
Quote:
Originally Posted by KTM250

Thanks guys for the replys. I believe that I understand most of this, but still have the question of doing the 2PT. So should I use 80 or 100% for the gain adjust. If I use 100 then once again I can use red and blue to balance the three and get a certain Y value or I could bring green up and then balance with red an blue which would give me a different Y value. It seems like there is more then one way to skin a cat here. As far as the 10PT goes I understand how to do that. I guess it goes back to how do I know that 100 is set correctly which is the base for all the rest.

If you do not have a 10 point adjustment, you typically use 30/80
if you have a 10 point, you do 2 point first, start at 100% adjust red and blue to get 100% as close as you can to balanced, and if it still is not close enough, adjust the green. The goal is to get rgb balanced the Y will be whatever it is. Y at 100% was set when you adjust Contrast and then the Backlight to achieve the fl output you want for your room. So the max Y is already set, when you do RGB at 100% you may lower or raise the previous set light output (Y). Then Y at all other input stimulus (90-10) are calculated from the 100%, what ever it ends up after RGB is balanced. This is where the never touch green came from. In the days of CRT and CRT projectors, every little bit of light was needed.. there was no backlight..
Quote:
Originally Posted by airscapes

Typically if the set only has 2 point you start with 80/30 get them close, then run the complete scale and make compromise adjustments to get everything as flat as you can.

If you have 10 point which will adjust gamma, you start with a 2 point using the 100/30.

Why would you not just use 80/30 for the 2 point initially just as you would if you didn't have 10 point adjustment available? I would suspect that you would initially want the curve to be as flat as possible and then fine tune it with the 10 point adjustment.

-Mark
Quote:
Originally Posted by Razz1

Why would you not just use 80/30 for the 2 point initially just as you would if you didn't have 10 point adjustment available? I would suspect that you would initially want the curve to be as flat as possible and then fine tune it with the 10 point adjustment.

-Mark

On my LG, I skip 2 point altogether and just do 10 point for both grayscale and gamma.

If you do choose to do 2 point first, I would use the control in the same way you would if you didn't have 10 point, choosing the closest gamma preset (and closest color temp preset) and getting RGB balance as close as possible across the entire grayscale. I would only use red and blue controls for 2 point, since messing with green has the same effect as changing the main contrast and brightness controls.

There is no one correct method for grayscale/gamma when you can do both 2 point and 10 point but I would choose the closest gamma preset prior to fine tuning gamma with the 10 point controls. How you do RGB (relative) balance is up to you, though choosing the closest color temp preset is still a good idea.
Quote:
Originally Posted by Razz1

Why would you not just use 80/30 for the 2 point initially just as you would if you didn't have 10 point adjustment available? I would suspect that you would initially want the curve to be as flat as possible and then fine tune it with the 10 point adjustment.

-Mark

Well, I don't know where I read/heard this or why it is in my head. I have looked and can not seem to find it. Since I have no way to quantify the idea of using 100 rather than 80 I will have to back peddle and agree there is little difference. If I find the source of this idea, I know I read it more than once from someone I have great faith in, I will post it for additional discussion.
In my quest to find the source, I have talked to several folks including spectracal support and 30/80 is still typically what you use with or without 10 point. Sorry for the confusion.
Quote:
Originally Posted by airscapes

Well, I don't know where I read/heard this or why it is in my head. I have looked and can not seem to find it. Since I have no way to quantify the idea of using 100 rather than 80 I will have to back peddle and agree there is little difference. If I find the source of this idea, I know I read it more than once from someone I have great faith in, I will post it for additional discussion.
In my quest to find the source, I have talked to several folks including spectracal support and 30/80 is still typically what you use with or without 10 point. Sorry for the confusion.

I don't know if this is correct, but when I do a 10pt, I do 2pt 100/30. Then when I go to do 10pt, starting point (100) is as good as I can get it.
Quote:
Originally Posted by airscapes

Well, I don't know where I read/heard this or why it is in my head. I have looked and can not seem to find it. Since I have no way to quantify the idea of using 100 rather than 80 I will have to back peddle and agree there is little difference. If I find the source of this idea, I know I read it more than once from someone I have great faith in, I will post it for additional discussion.
In my quest to find the source, I have talked to several folks including spectracal support and 30/80 is still typically what you use with or without 10 point. Sorry for the confusion.

Quote:
Originally Posted by ElectronicTonic

I don't know if this is correct, but when I do a 10pt, I do 2pt 100/30. Then when I go to do 10pt, starting point (100) is as good as I can get it.

Why focus on just 30/80 or 30/100? I'd get the lowest overall error across the entire grayscale. Then you could fine tune RGB balance wherever needed and flatten gamma to a targeted value (like 2.22) with the 10 point.
Well looks like was was researching a Samsung found this thread..
http://www.avsforum.com/avs-vb/showt...2#post21409582
I know it was someplace else as well.. but apparently to my embarrassment not a hard rule for all sets with 10 points..
Quote:
Originally Posted by airscapes

Well looks like was was researching a Samsung found this thread..
http://www.avsforum.com/avs-vb/showt...2#post21409582
I know it was someplace else as well.. but apparently to my embarrassment not a hard rule for all sets with 10 points..

I just did 10-pt only on my LG with great results. So, at least on the LGs, there no need to overthink the whole process. Just make sure you start with the closest presets for gamma and color temp to minimize adjustments.
Quote:
Originally Posted by PlasmaPZ80U

I just did 10-pt only on my LG with great results. So, at least on the LGs, there no need to overthink the whole process. Just make sure you start with the closest presets for gamma and color temp to minimize adjustments.

LD550?
I have one.
Just did the 10pt and gamma.
looks good.
Color is crazy.
ran out of red, and could not lower blue enough.
Quote:
Originally Posted by CalWldLif

LD550?
I have one.
Just did the 10pt and gamma.
looks good.
Color is crazy.
ran out of red, and could not lower blue enough.

LK450

when you say you ran out of red and couldn't lower blue enough, what color temp preset did you start with?

what settings are you using and what do the graphs/charts look like? you should be able to calibrate to D65 with the supplied picture settings/controls
Quote:
 Originally Posted by PlasmaPZ80U LK450 when you say you ran out of red and couldn't lower blue enough, what color temp preset did you start with? what settings are you using and what do the graphs/charts look like? you should be able to calibrate to D65 with the supplied picture settings/controls
42 LCD/CCFL
warm
expert1 ISF mode
grayscale and gamma were easy. went to do color gamut and all said and done, there is no more adjustments to increase red saturation. And I have blue bottomed out trying to get a balance with red.
here is a chc file.
all started with green being under saturated and hue was towards red.
had to move tint to 10+Green.
I was willing to have under saturation and could not lower blue sat or move its hue.

Quote:
Originally Posted by CalWldLif

42 LCD/CCFL
warm
expert1 ISF mode
grayscale and gamma were easy. went to do color gamut and all said and done, there is no more adjustments to increase red saturation. And I have blue bottomed out trying to get a balance with red.
here is a chc file.
all started with green being under saturated and hue was towards red.
had to move tint to 10+Green.
I was willing to have under saturation and could not lower blue sat or move its hue.

I'm assuming you have the *VA panel? The S-IPS version I have has a basically perfect gamut (with all dE94's under 1.0).

You may want to try increasing the main color control if you cannot increase luminance for any given color with the CMS controls alone.

Look at delta luma for the primaries and secondaries, especially blue. The 'color' controls in the CMS affect luminance more than saturation so use them and the main 'color' control to minimize delta luma for each of the six colors. Don't try to use the LG CMS to adjust saturation, especially for undersaturated colors as that won't be possible.

Also, I'd only make small changes to the CMS to avoid potential problems like banding. Do the best you can with the main color and tint controls first and make sure you choose BT709 for the color gamut option on the TV.
I have the IPS panel.
I will play with it more.
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