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LG PF1500G showing posterization after CMS calibration

2K views 9 replies 3 participants last post by  Jon65 
#1 ·
Hi,

I've tested esegan's calibration on my PF1500G (EU version), and at first the imaged looked great with very accurate color, but then a blue sky with lots of posterization appeared. I've found out that it was the CMS adjustments that were causing the problem, there's no problem with white balance. The EU version has RGBCMY adjustments for saturation, tint and luminance ranging from -30 to 30, it's the same for the LG PF1500 (US version)? This is driving me crazy, what causes this problem?

Please help!!!
 
#2 ·
The problem is unfortunately common with certain calibration settings on many LG TV's and projectors...the CMS controls for Luminance and Saturation as well as the 20point white-balance don't make their adjustments smoothly and instead affect only a super narrow point of their spectrum which means adjustments beyond -5/+5 or -10/+10 can easily cause visible banding. The CMS tint control is a tiny bit better behaved but not much, and the 2point white-balance isn't nearly as problematic.

You'll want to get the adjustments as ideal as possible first using just the main Color and Tint controls as well as the closest white-balance preset and then the 2point WB-adjustment.

For adjusting the 20-point and CMS, have a smooth black-to-white gradient handy to check exactly how far you can tweak the 20point before greyscale banding occurs, and use a smooth multi-color gradient for checking how far you can go with the CMS..I'll try to find and post the little custom one I used for my LG.
 
#3 · (Edited)
The problem is unfortunately common with certain calibration settings on many LG TV's and projectors...the CMS controls for Luminance and Saturation as well as the 20point white-balance don't make their adjustments smoothly and instead affect only a super narrow point of their spectrum which means adjustments beyond -5/+5 or -10/+10 can easily cause visible banding. The CMS tint control is a tiny bit better behaved but not much, and the 2point white-balance isn't nearly as problematic.
Hi Ftoast,

Yes, you're right, I've reached the same conclusion, posterization occurs if the color saturation and/or luminance is/are adjusted beyond -5/+5 or -10/+10. :(

You'll want to get the adjustments as ideal as possible first using just the main Color and Tint controls as well as the closest white-balance preset and then the 2point WB-adjustment.

For adjusting the 20-point and CMS, have a smooth black-to-white gradient handy to check exactly how far you can tweak the 20point before greyscale banding occurs, and use a smooth multi-color gradient for checking how far you can go with the CMS..I'll try to find and post the little custom one I used for my LG.
Do you have a LG PF1500 or PF1500G? If you have, can you show me your calibration settings? Please!

I appreciate your help,

Regards,
Danny
 
#5 ·
For my PA75u, its most visible accuracy problems are due to a really bold/fluorescent green primary and a green-ish/cold yellow secondary..the W/Balance defaults are either a ways warm or cold, but I'm usually fine with the warm W/B.

I have to dial main Color back a little around 45-49 for the more accurate skin-tones and I crank the main Tint control over about 5+points just to help get yellow and green to a better place at the expense of the other primaries/secondaries...Then I use the CMS to fix the damage I did to the other primary/secondaries and further improve the green and yellow.
I've got it set so there IS some visible pseudo-banding in that pattern I posted (less abrubt than most content banding but definitely showing some heavy leaning in that sensitive pattern).
This has let me get green and yellow to a much more natural place without badly hurting anything else AND without adding visible banding in actual content (I first noticed the banding in certain animated scenes since most of my adjustment was to yellow and green rather than sky-tones).

While LG has done a particularly poor job with their CMS/20point response, many other manufacturers are guilty to a lesser extent of the same thing. Worst of all, most professional test-patterns and the overall calibration graph don't show these kinds of problems, so often only a calibrator who takes the extra time to view actual content (and even then, only the specifically affected content which shows it) will notice.
I'm surprised using simple gradients like the one above aren't more wide-spread for checking errors like this..I'm certainly NOT a professional calibrator, so I just made my own pattern quickly on a whim because it made sense for detecting the problems I was finding more easily.
 
#7 ·
I don't have a colormeter either (found out even a nice spectro needs to be sent in for re-calibration every 1-2years which costs around $100-$150 I think...decided it wasn't worth it).
I just used the gradient pattern by connecting my computer to the LG's HDMI input, opening it up in paint and then seeing how far I could adjust each aspect of the LG's CMS before banding got totally out of control.
This is how I learned about how far I could tweak the CMS saturation and luminance before things got ugly AND where I found out exactly how limited those controls are for adjusting their colors (since they mostly only affect a very small point rather than moving that point and gradually everything near/around it).
On my LG the CMS tint control has a little more effect than the saturation and luminance CMS controls, so I can nudge it as much as -10/+10 or even -15/+15 if needed while the luminance and saturation CMS controls are better left within -5/+5 for mine.

Because I don't have a colormeter, I was just adjusting out the really obvious color errors I could easily see by eye and also by comparison to other nearby displays that I know are at least in the ballpark of correct.
 
#9 ·
Most LCD/LED televisions are surprisingly accurate nowadays. If you've got a fairly new TV, I'd check www.rtings.com to see if they have it listed because they measure their TVs to post how accurate they are out-of-the-box AND then calibrate them and post the calibration settings. Granted, they aren't necessarily all that perfect from one set to another, but I've noticed patterns from panel-readings and it seems like the larger errors are often repeating and pretty easy to fix by copying settings from another set of the same exact model..that's assuming the set even HAS larger errors to begin with!

The settings-tweaking can be pretty fun in a "I'm totally a geek for this" kind of way.
Those main controls on the LG all work really well and the White-Balance presets (and I think the 2point W/B settings) work well too. From what I remember seeing with LG's earlier 1080 LED model (the larger, flatter one that cost a bit more released a year before the pf1500) the primaries are a lot more accurate now than they were with something like my PA75u, so at least those fine CMS details are probably at a much more accurate starting-point compared to mine even if you don't adjust them or just nudge them a little bit.

Now because of you I'm probably going to mess around with my LG's 2point and 20point W/B to see what happens since I haven't played with the settings in over a year.
 
#10 ·
I did a calibration on an LG B6 a couple weeks ago using calman. Got great looking charts, but resulted in the posterization, which led me to this thread.

I did a C6 yesterday. Same thing. But, I backed off the red saturation and everything cleared up. Sweet! Also may need to back of magenta as well if that is causing any issues. Everything else I left as it was after the calibration and things looked great.

Hope this helps someone.
 
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