stubborn RGB on samsung - AVS Forum
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post #1 of 16 Old 12-20-2012, 06:24 AM - Thread Starter
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I have a LN52B750 that is several years old. I calibrated it when I got it with an i1 LT, but a few months ago I bought the better i1 Display 3. I figured I'd re-calibrate my TV to see if anything changed over the years. Things went OK, but I'm running into the same problem that I did back then. The grayscale has this pesky blue hump in the middle. I can lower the blue offset to get the middle correct, but then there's not enough blue down low. It seems like the closer I get the middle, the worse the upper and lower ends of the grayscale get. It's the same with the red. If I raise the R offset to get a little more red near the 40-50% range, there's way too much red down low. Here's what I came up with last night (see pics). my settings are:

White Balance:
R-Offset: 25
G-Offset: 25
B-Offset: 25
R-Gain: 35
G-Gain: 25
B-Gain: 23


The screencaps are with the R offset at 26, but after calibrating, I looked at a grayscale ramp and the darker parts looked slightly red. I lowered the R offset to 25 and that seemed to help.






Other settings:

Mode: Movie
Backlight: 4
Contrast: 98
Brightness: 45
Color: 49
Tint: G49/R51

Gamma: +2
Color Space: Auto
Color Tone: Warm2
Black Tone: Off
Dyn. Contrast: Off
Flesh Tone: 0
Edge Enhance: Off
xvYCC: Off

Size: Screen Fit
Digital NR: Off
HDMI Black Level: Greyed Out (or low for cable box)
Film Mode: Greyed Out (or Film 1 for interlaced material)
Auto Motion Plus: Custom

Blur: 10
Judder: 0 (or 3 for TV)

Game Mode: Off
Energy Savings: Off

Service Menu:
CE Dimming OFF
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post #2 of 16 Old 12-20-2012, 07:14 AM
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Seeing that your R-Gain is at 35 tells me that you clipped your red a long time ago and now are trying to compensate for it. Set your white balance back to default 25's, and take readings of a 100% window starting with your contrast at 80. Watch the red while increasing your contrast 1 click at a time. At some point red will stop increasing and start decreasing the percentage. This is your red clipping point. My A650 red clipping point is a contrast setting of 89, YMMV. This may help with the deficiency of blue on the top end and flatten things out. Play with the gamma setting also. The gamma setting on Samsung's are global, so if you still have a hump, this will move it up or down the grayscale.
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post #3 of 16 Old 12-20-2012, 07:32 AM - Thread Starter
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Originally Posted by duke32 View Post

Seeing that your R-Gain is at 35 tells me that you clipped your red a long time ago and now are trying to compensate for it. Set your white balance back to default 25's, and take readings of a 100% window starting with your contrast at 80. Watch the red while increasing your contrast 1 click at a time. At some point red will stop increasing and start decreasing the percentage. This is your red clipping point. My A650 red clipping point is a contrast setting of 89, YMMV. This may help with the deficiency of blue on the top end and flatten things out. Play with the gamma setting also. The gamma setting on Samsung's are global, so if you still have a hump, this will move it up or down the grayscale.

Thanks, I will give this a try. The reason I had contrast set so high, is that 95-100 seems to be the usual contrast setting everyone uses on this model. Even at contrast 100, the whites don't clip, and there is no discoloration. I settled on 98 and backlight 4 because that gives me right around 30 ftL for 100% white.
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post #4 of 16 Old 12-20-2012, 07:18 PM
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If your model does not have Samsung's 10-point grayscale controls, there may be NOTHING you can do to fix a hump in the middle. If your models DOES have 10-point grayscale controls, you should set the 2-point controls to get the grayscale sort of OK, then fix remaining problems with the 10-point adjustments.

Whenever you have a situation where 1 or more colors "cross" each other in the RGB Balance graph, you can't usually fix the problem with 2-point adjustments... you have to have something "more" like 10-point controls (20-point in some LG models) in the TV or an external video processor with 10 or more adjustment points.

If you can manipulate the gains and offsets to get red, green, and blue to be parallel or to cross each other no more than 1 time, you can get pretty good results with 2-point grayscale controls. But once you have a situation where any one (or more) colors cross each other more than 1 time in the RGB Balance graph, there's really nothing you can do to fix it with gain/offset controls alone (assuming you haven't gotten any one (or more) gain or offset out in the weeds somewhere).

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post #5 of 16 Old 12-21-2012, 07:13 AM - Thread Starter
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Quote:
Originally Posted by Doug Blackburn View Post

If your model does not have Samsung's 10-point grayscale controls, there may be NOTHING you can do to fix a hump in the middle. If your models DOES have 10-point grayscale controls, you should set the 2-point controls to get the grayscale sort of OK, then fix remaining problems with the 10-point adjustments.
Whenever you have a situation where 1 or more colors "cross" each other in the RGB Balance graph, you can't usually fix the problem with 2-point adjustments... you have to have something "more" like 10-point controls (20-point in some LG models) in the TV or an external video processor with 10 or more adjustment points.
If you can manipulate the gains and offsets to get red, green, and blue to be parallel or to cross each other no more than 1 time, you can get pretty good results with 2-point grayscale controls. But once you have a situation where any one (or more) colors cross each other more than 1 time in the RGB Balance graph, there's really nothing you can do to fix it with gain/offset controls alone (assuming you haven't gotten any one (or more) gain or offset out in the weeds somewhere).

Thanks:) Unfortunately, my TV only has the 2-point controls. If you take a look here, you can see a before and after from when I calibrated a few years ago:

https://sites.google.com/site/calibrationb750/home/before--after-calibration

After playing around for hours the other night, I still came up with practically the same white balance settings.

White Balance (initial cal. from a few years ago) vs White Balance (most recent)
R-Offset: 25 / 25
G-Offset: 25 / 25
B-Offset: 26 / 25
R-Gain: 34 / 35
G-Gain: 25 / 25
B-Gain: 23 / 23

Anyway, my grayscale ramp looks reasonable. I noticed a slightly reddish area in the low end the other night, so I bumped the R-offset down to 25 from 26, and it seems better. I haven't re-measured yet, but I think that'll probably help lower my large delta E at 20% that you see in my original post. it looks like I could bump up the B-offset 1 notch, but I think that will also make the middle blue hump worse.

Guess it's time for a new TV with fancy 10-point adjustment, hehe;)
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post #6 of 16 Old 12-21-2012, 04:13 PM - Thread Starter
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Well, I played around with the controls a bit more and wound up with this:




This is what happens when I get the 20/30% and 80% gray looking good. Settings are just slightly different than before...

R-Offset: 24
G-Offset: 25
B-Offset: 26
R-Gain: 35
G-Gain: 25
B-Gain: 25

I guess I will just have to accept the blue hump. Grayscale ramps and patterns look reasonable, and the picture looks fine with HD and Blu-ray. The more I try to fix the hump, the worse the high and low ends get.cool.gif
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post #7 of 16 Old 12-21-2012, 04:24 PM
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When you were done, did you recheck and set brightness and contrast verifying you are not clipping any colors?
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post #8 of 16 Old 12-21-2012, 06:13 PM - Thread Starter
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Quote:
Originally Posted by airscapes View Post

When you were done, did you recheck and set brightness and contrast verifying you are not clipping any colors?

I think so. I went through the basic patterns on the AVS 709HD disc, and they looked good. I looked at the color clipping pattern, and they were all distinguishable.

Also, I tried playing with the contrast, like someone mentioned above. I loaded up a 100% white window and turned the contrast down. I raised it a notch at a time, and watched the red level. It never got to a point where it started decreasing, even at contrast 100. I just left the contrast at 98, though.
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post #9 of 16 Old 12-22-2012, 01:28 PM
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The art of calibration comes from knowing what compromises to make when the TV has issues that can be completely resolved with the available controls and the native limitations of that particular TV. There can be times when leaving one error uncorrected while fixing other errors looks best... other times you may get better-looking images if you fix 50% or one error and 50% of the other error (though it's unusual to have a situation where you have that precise of an option).
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post #10 of 16 Old 12-23-2012, 09:01 AM - Thread Starter
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Quote:
Originally Posted by Doug Blackburn View Post

The art of calibration comes from knowing what compromises to make when the TV has issues that can be completely resolved with the available controls and the native limitations of that particular TV. There can be times when leaving one error uncorrected while fixing other errors looks best... other times you may get better-looking images if you fix 50% or one error and 50% of the other error (though it's unusual to have a situation where you have that precise of an option).

I played around a bit more with it and I guess I'm sticking with:

R-Offset: 25
G-Offset: 25
B-Offset: 26
R-Gain: 35
G-Gain: 25
B-Gain: 23

I guess these settings make sense, because when I did my "before" measurements, the red was low all the way across the grayscale, green was close, and blue was close, but had the hump in some places. Below, you'll see my before RGB with WB at default and color at warm2. The after results are below that.

BEFORE


AFTER



I got some fairly decent Delta E values, except for the very middle section, but that's about as much as I can reduce the "hump" without messing up the high and low ends.
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post #11 of 16 Old 12-26-2012, 01:09 PM - Thread Starter
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Also, anyone know if calibrating the grayscale through the service menu would give me better results, or would I just end up with the same thing?
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post #12 of 16 Old 12-26-2012, 01:41 PM
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Originally Posted by milehighou View Post

Also, anyone know if calibrating the grayscale through the service menu would give me better results, or would I just end up with the same thing?

Usually the service menu might have finer steps, or a larger range but it wouldn't effect this kind of problem.

I have a toshiba LCD that was the first TV I really tried to calibrate that had almost this exact problem.
The only real solution is to up your high end red a bit (or drop green and blue) and just live with it, I spent probably 50 hours tinkering and remeasuring to see if I could fix a hump like that (and also a gamma dip), but the truth is when you only have 2 points of control you just have to live with results like that (and they really aren't all that bad).

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post #13 of 16 Old 12-26-2012, 02:16 PM - Thread Starter
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Originally Posted by sotti View Post

Usually the service menu might have finer steps, or a larger range but it wouldn't effect this kind of problem.
I have a toshiba LCD that was the first TV I really tried to calibrate that had almost this exact problem.
The only real solution is to up your high end red a bit (or drop green and blue) and just live with it, I spent probably 50 hours tinkering and remeasuring to see if I could fix a hump like that (and also a gamma dip), but the truth is when you only have 2 points of control you just have to live with results like that (and they really aren't all that bad).

LOL, thanks. I know how that goes. I don't know if I spent 50 hours, but I know I've passed quite a few messing with the gray controls. I will probably just leave well enough alone until I get a new TV some day. I think the picture looks good now. It'd be nice to get below that magical 3 delta E number, but oh well:cool:
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post #14 of 16 Old 12-30-2012, 06:14 PM - Thread Starter
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Well, I don't know if this is much better, but I did a little more tweaking. I raised the contrast to 98 because my light output at 100% white was a tad low. It is now 30.5 ftL.

Instead of tuning at 80 and 30%, I kept going back and forth between 25 and 75%. The graph looks like I should bump up the red offset, but the low end just looks too red if I do that. Anyway, for WB, I settled on:

R-Offset: 25
G-Offset: 25
B-Offset: 27
R-Gain: 35
G-Gain: 25
B-Gain: 22

Not much of a difference from my original settings, but I watched a blu-ray last night, and everything seemed great.


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post #15 of 16 Old 12-31-2012, 03:22 PM
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Hey, what meter are you using? I think you are the first to calibrate to a non conventcional percentage of white pattern. I think you should just go back to 80 and 20 or 30. Looking at your 80 % white results when you calibrated using 80/20 or 30 it's at a delta e of 2.6. Still seems like it should be lower if you set your white balance properly to x313 y329 try to hit this point for both 80 and 20 % of white. Then take a full measurement. I realise you only have 2 points in controlling the grey scale then getting the middle closer and sacrificing at the high end is the better way to go. The delta e for the majority are in the "visible" range. If this is the best the tv can do then sorry to say you have to live with it.
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post #16 of 16 Old 12-31-2012, 10:04 PM - Thread Starter
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Hey, what meter are you using? I think you are the first to calibrate to a non conventcional percentage of white pattern. I think you should just go back to 80 and 20 or 30. Looking at your 80 % white results when you calibrated using 80/20 or 30 it's at a delta e of 2.6. Still seems like it should be lower if you set your white balance properly to x313 y329 try to hit this point for both 80 and 20 % of white. Then take a full measurement. I realise you only have 2 points in controlling the grey scale then getting the middle closer and sacrificing at the high end is the better way to go. The delta e for the majority are in the "visible" range. If this is the best the tv can do then sorry to say you have to live with it.

It's the i1 Display 3 pro.

I was also looking at 80 and 30% when calibrating, but the big change always seems to happen when going from 20 to 30. 20 will be too red, and then 30 will be too blue.

I dropped my blue offset down 1 click from 27 to 26, and I think I'm just gonna leave it like that. Didn't feel like setting up and re-measuring everything, but going by the rgb graph above, that seems like a reasonable thing to do. Grayscale ramp and steps looks good visually. I wish I had 10-point grayscale adjustments, but with only 2-point, there's only so much I can do.
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