GrayScale Calibration

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.


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.





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.

What type of Display are you calibrating?

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.

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..

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.

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.

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..

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.

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.

 

bestlglcdr.zip 1.2705078125k . file

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.