Red pixels still glow when setting Samsung LCD screen to Green only filter... what to think of it? - AVS Forum
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post #1 of 14 Old 09-26-2013, 12:19 PM - Thread Starter
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Hello all, sorry for opening a new thread I couldn't find a related thread...

If possible, I'd like to get some expert advice or clarification regarding an issue with the green RGB mode in my Samsung UE32F5000.
32A6AF0S in service menu.

I'm an almost total noob regarding display calibration.
Calibration settings before noticing green RGB mode issue: (by eye, no calibration equipement used)
For setbox connected to HDMI1 port of TV.

Preset: Movie
Backlight: 17 (Depends on ambient ilumination)
Contrast: 95
Brightness: 45
Sharpness: 0
Color: 53 (don't remember why I put this value)
Tint: 50/50
Gamma: 0
Color Tone: Warm 1
HDMI Black level: Normal
Color Space: Auto
Screen size: Screen fit
Film Mode: Auto 1 (can't see difference with Auto 2)
Dynamic Contrast: Disabled
LED Motion Clear: Disabled
Digital/MPEG Noise Filter: Disabled
Black tone: Disabled

White Balance:
Red Offset 20
everything else 25

Everything else untouched or at stock settings...

I recently acquired a loupe to be able to scrutinize the subpixel structure of the panel.
With the loupe I also took the opportunity to see what sort of changes were happening within the pixels when changing calibration settings... nothing worth mentioning until I looked at the RGB mode.

Selecting red or blue modes expectedly lightened up only the corresponding RGB componets of the pixels, but in green mode I noticed that besides the green subpixels also a little part of the red subpixels got slightly iluminated in an area of the screen that in non RGB mode was actually white, pure white.... only on the white area of the picture the red subpixels where lightened up...

For ilustration purposes I'll upload the following picture (I can't take a picture of mine):
Note that this picture is not representative of the subpixel structure in my screen, it's different.



What I described is the opposite of this, the green subpixels fully lightened up and the a little portion of the reds also slightly lightened.
I obviously can't discriminate the subpixels by naked eye, so only through the lupe I can see it.

I guess this isn't normal as only one color should lighten up, correct?
Is this a normal miscalibration/or oversaturation issue or is there some problem with my TV?

Before discovering this I had already noticed that the images on my display often look a bit to reddish, noticeable in peoples faces, and also had noticed that if I raise the Contrast setting very high past 95 there will be a color shift in whites becoming less red and more green or cyan... also noticed that greys look a bit red to...

I'd like to ask if this is addressable through the two point white balance controls?

I have experimented lowering the red offset until the red subpixels got lightened off in green mode with success.
But I had to lower the red offset to at least 6... which seems like a bit to much but I don't know...
After doing this I was initially pleasently surprised with the effect this simple change had on the images of my TV, grays didn't look red anymore and whites didn't color shift anymore when raising Contrast setting to max and greens and blues looked much more well saturated, peoples faces were in general more believable without the red tint.
But now there seemed to be a bit to much green in the mix so I lowered the green offset until it seemed reasonably balanced, I lowered it to 20... now there was to much blue lol.
At this point I noticed that blacks were starting to get crushed and the overall brightness of the pics was decreased and further lowering of the green and blue offsets to try to get the right (absolutelly subjective) balance just augmented those issues.
I eventually settled with a red offset of 5, green offset of 16 and blue offset of 20.
With these settings I was able to counteract the decreased brightness and eliminate the black crush just by raising gamma to "+2"...
However after this gamma adjustement I noticed that the red subpixels got slightly lightened up again (much less now) when in green RGB mode on a corresponding white area of the picture, but I didn't notice any red tint now, actually the dark areas, in some movie scenes, had an unnatural blue tint to them... but overall the picture seemed to look better fine detailed and transparent as if a dirty layer had been removed from the screen...

At this point I stopped and thought about asking for some help or guidance here at avsforum... I forgot to check if there was any color shift at white peaks again...
Unfortunatelly my setbox cannot playback any video files of mine, I can't use any test patterns to do basic callibration for my setbox it seems... unless I try to hack it's network settings to stream a video from my PC into it but that's too much hassle lol.

But anyway, I'd like to have some expert explanation or opinion or advice about my issue here with the green RGB mode and the best way to eliminate the red omnipresent glow, or at least an explanation/interpretation of what this might mean.

Any input will be greatly apprecciated!
Apologise for wall of text.
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post #2 of 14 Old 09-27-2013, 04:41 PM
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Don't use RGB mode on that TV than, simple as that. End of discussion. It happens. Most of the time, RGB and YCbCr modes look identical. Occasionally you find cases where YCbCr looks a little better than RGB or vice versa. If you have one of those TVs, use the mode that looks better and forget about it. Nothing you can do about it.

There is nothing gained by using RGB mode anyway. And using a loupe to look at pixels... sheesh, calibrators don't even do that because it doesn't really tell you much about how images will look.

And stay OUT of the damn service menu. Samsungs are the most often whacked TVs by people who ignore the warnings and go into the service menu. STAY OUT of there... there's nothing in there you need to calibrate the TV. User Menu settings have all the controls. And you can't do anything useful without a meter and calibration software with the calibration controls anyway. Even if you THINK you are doing the right thing, there's about a 75% chance that you are NOT helping because human vision is EASILY fooled by things you are unlikely to be taking into account. And even if you knew all of the things that throw your perception off, you still can't do anything about them by eye, because your vision will simply NOT allow you to see the images correctly when there are one or more perception-whacking factors in play.

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post #3 of 14 Old 09-27-2013, 04:47 PM
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+1 What Doug Said!
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post #4 of 14 Old 09-27-2013, 04:54 PM
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And by the way, there's no such thing as a "subpixel" you can see. It is a concept, not a physical thing. You are looking at pixels when you look thought a loupe. Plasma pixels can only be on or off, nothing in between. So each red pixel can only be 0% red (black) or 100% red. To get a shade of red somewhere between 0 ad 100, pixels are flashed on and off many times per frame and there is some dithering added so all the 12% red pixels aren't all flashing on and off at the same time because that could be visible in the image.

The rate the pixels are flashed on and off is the subpixel rate. You can see the flickering pixels easily at illumination levels below 10% and you may see it even higher than that. But by the time you get to 25% or 30%, pixels appear to be pretty steadily illuminated even though they are flickering. What happens to a given pixel during 1 specific frame (1/60th of a second) happens at the subpixel level but you cannot see subpixels. 50% red is created by flickering each red pixel that is supposed to be at the 50% level for 1/2 of the frame interval... half of 1/60th of a second. So if there are 10 pixel flickers per frame available, 50% red would require the 50% red pixels to be on for 5 flickers and off for 5 flickers, but to keep this from being visible, the flickering is randomized so one red pixel might be on-off-on-off, etc while another red pixel might be on-on-off-off, etc. while another pixel might be on-off-off-on etc.. When you reproduce something like 5% white, most of the pixels will be off most of each frame so you end up with a 5% area that looks like a bunch of mosquitoes flitting about rather than looking like a solid gray area. Until you move far enough away that you can no longer see pixels or groups of pixels.
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post #5 of 14 Old 09-28-2013, 12:05 PM - Thread Starter
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Thanks for your reply Doug Blackburn...

I'm not sure you understood the issue on my TV screen though... maybe I didn't explain it correctly.
I don't think this has anything to do with differences between RGB and YCbCr color spaces.
I think my setbox is probably sending a 0-255 RGB color space to my TV because I have to set "HDMI Black level" to Normal otherwise I'll get black crush.
I guess I would have to test with another source that can send either color space and see if the issue remains... just to be sure...

But for clarification and completeness sake I'll try to explain further:

In the Picture settings of the User Menu (NOT Service Menu, I didn't even know one could calibrate through the Service Menu...) of my Samsung UE32F5000 LCD (not Plasma) there's a setting called "RGB Only Mode":
http://www.samsung.com/us/support/howtoguide/N0000000/9413/0/N/4/M//

"RGB Only:

The RGB Only Mode option is used for calibration purposes only. With this option turned on the TV can apply a Red, Green, or Blue filter for use when calibrating the TV.

Important: The applied color filter will still be applied even after exiting the menu. To disable the color filter you must return to the RGB Only Mode and set it to off.
Off: Disables RGB Only Mode.
Red: Applies a Red Filter to the picture.
Green: Applies a Green Filter to the picture.
Blue: Applies a Blue Filter to the picture
."

When selecting one of those three color filters the screen will only show different shades of the selected color.
So when selecting red the only color that will appear on the screen is (different shades of) red, when selecting blue the only color on the screen will be blue and when selecting green the only color on the screen will be green.

Looking at the pixels of the screen through a loupe (just for curiosity sake) with the different filters I observed that with either Red or Blue filters selected only the Red or Blue pixels, respectivelly, where lightened up regardless of the shade/(corresponding color in any area of the picture with "RGB Only Mode" set to Off).
But with the Green filter in any area of the picture that corresponds to pure white (with "RGB Only Mode" Off), besides the Green pixels also a small part of the Red pixels was slightly iluminated, meaning less brilliant than the Green pixels but still glowing nevertheless.
This was a very clear thing to see, the pixel structure in pic on the first post is not to dissimilar of mine TV and the Red pixels were't flickering at all regardless of how low the intensity of their glow/light was.

What I'm talking about is the whole Green pixels glowing and about three squares(Bits?) of the Red pixels glowing to, but with less intensity. It's very easy to visualize with the picture on the first post, just like my TV panel each of the color pixel has 8 small squares/rectangules (not sure if should call them Bits since S-PVA panels are 8-bit per pixel?... nevermind) and each of them can glow independently and with different intensity from each other.

I hope the issue is easier to visualize now.

I don't really expect/demand an explanation or advice for this particular issue (although a constructive one would certainly be apprecciated).
But I assume it still could be an interesting subject for experts to discuss about, either from a manufacturing quality control or panel quality point of view as this could have some potential significance value for calibrators, costumers and alike...
So naive as this assumption of mine might be, I'm still admired (not in a good way) by the way how you simply dismissed this subject altogether... unless you didn't understand it right...

Anyway the thread is here for anyone with an interest to discuss this matter, if someone has any subject related thing to say feel free to express.

FWIW, I ended up leaving the two point white balance controls at the settings that gave me the best (striving for neutrality and accuracy but it's admitedly a personal assessment and non educated by any equipement/calibration reference) color balance on the screen regardless of/if the Red pixels glow in the Green filter mode.
But the acknowledgement of this issue through a loupe and the influences on the picture quality when trying to deal with it have made for a worthwhile learning experience for me.
The thing that most mattered in the end is to acquire the right balance of settings/variables rather than trying to acquire the purest/most perfect state for each visual element... probably indicative of LCD limitations afterall, or something of the kind...

Current calibration settings:
Color: 50

White Balance settings:

Red Offset: 20
Green Offset: 23
Blue Offset: 25
Red Gain: 30
Green Gain: 32
Blue Gain: 23

Everything else the same as in the settings in the above post.

Happy with it as it is right now.

Maybe I should change the title of this thread as it is not particularly clear...
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post #6 of 14 Old 09-28-2013, 12:15 PM - Thread Starter
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Thread title changed.
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post #7 of 14 Old 09-28-2013, 04:44 PM
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Quote:
Originally Posted by kkl10 View Post

Thanks for your reply Doug Blackburn...

I'm not sure you understood the issue on my TV screen though... maybe I didn't explain it correctly.
I don't think this has anything to do with differences between RGB and YCbCr color spaces.
I think my setbox is probably sending a 0-255 RGB color space to my TV because I have to set "HDMI Black level" to Normal otherwise I'll get black crush.
I guess I would have to test with another source that can send either color space and see if the issue remains... just to be sure...

But for clarification and completeness sake I'll try to explain further:

In the Picture settings of the User Menu (NOT Service Menu, I didn't even know one could calibrate through the Service Menu...) of my Samsung UE32F5000 LCD (not Plasma) there's a setting called "RGB Only Mode":
http://www.samsung.com/us/support/howtoguide/N0000000/9413/0/N/4/M//

"RGB Only:

The RGB Only Mode option is used for calibration purposes only. With this option turned on the TV can apply a Red, Green, or Blue filter for use when calibrating the TV.

Important: The applied color filter will still be applied even after exiting the menu. To disable the color filter you must return to the RGB Only Mode and set it to off.
Off: Disables RGB Only Mode.
Red: Applies a Red Filter to the picture.
Green: Applies a Green Filter to the picture.
Blue: Applies a Blue Filter to the picture
."

When selecting one of those three color filters the screen will only show different shades of the selected color.
So when selecting red the only color that will appear on the screen is (different shades of) red, when selecting blue the only color on the screen will be blue and when selecting green the only color on the screen will be green.

Looking at the pixels of the screen through a loupe (just for curiosity sake) with the different filters I observed that with either Red or Blue filters selected only the Red or Blue pixels, respectivelly, where lightened up regardless of the shade/(corresponding color in any area of the picture with "RGB Only Mode" set to Off).
But with the Green filter in any area of the picture that corresponds to pure white (with "RGB Only Mode" Off), besides the Green pixels also a small part of the Red pixels was slightly iluminated, meaning less brilliant than the Green pixels but still glowing nevertheless.
This was a very clear thing to see, the pixel structure in pic on the first post is not to dissimilar of mine TV and the Red pixels were't flickering at all regardless of how low the intensity of their glow/light was.

What I'm talking about is the whole Green pixels glowing and about three squares(Bits?) of the Red pixels glowing to, but with less intensity. It's very easy to visualize with the picture on the first post, just like my TV panel each of the color pixel has 8 small squares/rectangules (not sure if should call them Bits since S-PVA panels are 8-bit per pixel?... nevermind) and each of them can glow independently and with different intensity from each other.

I hope the issue is easier to visualize now.

I don't really expect/demand an explanation or advice for this particular issue (although a constructive one would certainly be apprecciated).
But I assume it still could be an interesting subject for experts to discuss about, either from a manufacturing quality control or panel quality point of view as this could have some potential significance value for calibrators, costumers and alike...
So naive as this assumption of mine might be, I'm still admired (not in a good way) by the way how you simply dismissed this subject altogether... unless you didn't understand it right...

Anyway the thread is here for anyone with an interest to discuss this matter, if someone has any subject related thing to say feel free to express.

FWIW, I ended up leaving the two point white balance controls at the settings that gave me the best (striving for neutrality and accuracy but it's admitedly a personal assessment and non educated by any equipement/calibration reference) color balance on the screen regardless of/if the Red pixels glow in the Green filter mode.
But the acknowledgement of this issue through a loupe and the influences on the picture quality when trying to deal with it have made for a worthwhile learning experience for me.
The thing that most mattered in the end is to acquire the right balance of settings/variables rather than trying to acquire the purest/most perfect state for each visual element... probably indicative of LCD limitations afterall, or something of the kind...

Current calibration settings:
Color: 50

White Balance settings:

Red Offset: 20
Green Offset: 23
Blue Offset: 25
Red Gain: 30
Green Gain: 32
Blue Gain: 23

Everything else the same as in the settings in the above post.

Happy with it as it is right now.

Maybe I should change the title of this thread as it is not particularly clear...

The red, green, or blue-only modes are for setting/checking color and tint, nothing more. They serve the same purpose as the color filters that come with some setup and test discs. Using your offsets and gains to adjust them is wrong. Those are for adjusting grayscale, not for color decoding. And you can't accurately adjust them by eye anyway.

The reason you are seeing red pixels lit along with green in Green-only mode is because your display is blending green and red to make its green primary.

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post #8 of 14 Old 09-28-2013, 08:15 PM
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ditto

There may (or may not) be a native color mode that will have very inaccurate and oversaturated primaries (or perhaps only 1 or 2 primaries are oversaturated). When you select a more appropriate mode where the primaries are more accurate... it doesn't happen by accident. Something has to happen to make green more accurate. If green is oversaturated, about the only option to desaturate it to make it accurate would be to add red... or possibly blue (depending on where the green point actually was) or you may have to add red AND blue to desaturate green to make it accurate.

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post #9 of 14 Old 09-29-2013, 08:31 AM - Thread Starter
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I see... I guess that's how it works then...

Initially when I lowered the Red offset until the red pixels weren't glowing anymore in the green filter, I didn't notice any difference in the saturation or luminance of the filter at all.
But when I disabled the filter and looked at normal images there was a lot of difference, definitely to much green tint.

In the end I just ignored the issue and didn't try to adjust the green filter with the offsets nor gain controls, I know that's wrong.
I tweaked the white balance controls with normal pictures, with the color filters Off, where whites, flesh and greys or shadows were abundant (I know it's not accurate by eye but what else can I do?...).
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post #10 of 14 Old 09-29-2013, 02:29 PM
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What else can you do? Really? You can spend 100 or more hours reading and practicing calibration until you get fairly good at it... and spend some money on a meter and software you need for calibration. Or you can hire a professional calibrator to do the calibration for you saving you the time, effort, and cost of doing it yourself.

Your eyes have about as much chance of making things better as selecting settings blindly (within reason, of course, most controls have far more adjustment range than is really needed).

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post #11 of 14 Old 09-29-2013, 03:50 PM - Thread Starter
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Well that's easy to say but to do it's a different story. rolleyes.gif
The part about reading and practising is not a problem for me, the problem is that I'm not exactly sitting on a pile of money...
I only spent around 306 euros with this TV afterall.
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post #12 of 14 Old 09-29-2013, 03:55 PM
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Greetings

Options

1. Learn it all yourself ...buy your own gear and spend time over the next year scrounging around for tidbits of information. (You will get to the right answer ... eventually ... maybe.)

2. Hire a professional to come and do it and hope he will also educate you some over the 4 hours that he is there. Or hire the wrong professional and the person is in and out in 45 min. Your TV is calibrated, but you don't understand how or why.

3. Get professional level training on how to calibrate with your own gear. (Costs anywhere from $100 to $1600 or more and spending more does not mean it is better.)

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post #13 of 14 Old 09-29-2013, 04:05 PM - Thread Starter
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Greetings there

Option 4. Make friends with a professional calibrator and invite him for a diner. tongue.gif
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post #14 of 14 Old 09-29-2013, 04:37 PM
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Greetings

It kind of comes back to your time being worth little to nothing again. Go spend your time looking for that special calibrator that will do this for you. Teach you in exchange for a dinner. Like everyone that is an engineer also has the aptitude to teach others to be an engineer. Doesn't quite work that way.

A couple of dinners and you are half way to the cost of professional training anyway.

But you are allowed to dream on though.

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