Folks,

I posted this to a couple of other threads, but received no responses.

Is there but one completely correct RGB calibration for an individual panel (or A/V mode for a panel with multiple memories), or are there many? In other words (using my Pioneer 5020 plasma as an example), could I get my RGB levels to 100% each with more than one combination of RGB settings, say R 457, G 480, B 505 and R 488, G 496, B 552?

If both COULD have all three levels at 100%, would they both yield the same color temp (I think they would)? Would there be a difference in the picture, theoretically? Advantages to doing it one way or the other?

I know there are many other factors involved, but I'm just trying to understand the impact of the RGB levels in doing a DIY calibration.

Thanks,

poormxdad

Greetings

There can be many right answers. It comes down to where you set your contrast and brightness ... and the variance in the components of the TV and a number of other things.

5+5=10 ... but so does 8+2=10 ... and 3+3+4 ... and so forth.

regards

Is there but one completely correct RGB calibration for an individual panel (or A/V mode for a panel with multiple memories), or are there many? In other words (using my Pioneer 5020 plasma as an example), could I get my RGB levels to 100% each with more than one combination of RGB settings, say R 457, G 480, B 505 and R 488, G 496, B 552?
For a given set of primaries, there will be one and only one algebraic combination of them that will exactly produce D65. That being said, as Michael indicates, you do calibrate to a tolerance and that means multiple paths to the goal. Unit-to-unit variation will mean that the combination of controls required to get "close enough" to D65 on your panel are unlikely to match many other users' settings. However, if you could pull together all of the control values for all of the calibrated sets for your model, you would probably see a reasonably tight distribution of values for each control, but you would still need to do measurements to figure out where in that distribution your particular set fell.

If both COULD have all three levels at 100%, would they both yield the same color temp (I think they would)? Would there be a difference in the picture, theoretically? Advantages to doing it one way or the other?
I'm not quite sure what you are asking. If your meter has decent-enough precision (repeatability), then different values ought to produce slightly different measurements, unless the controls were so granular that the changes were beneath the meter's ability to differentiate them.

Bill

Bear,

I'm not sure how to ask it differently, but here goes...

Let's say I'm using HCFR and calibrate the RGB levels on my 5020. With Red at 500, Green at 500, and Blue at 500 (just for simplicity) HCFR tells me in Continuous Read mode that all the levels are at 100% at all percentages of Gray. I should have 6500k color temp. Soooooooooooooo, then I bump Green to 505, and chase Red and Blue till HCFR again tells me all the levels are at 100%. I should also read a 6500k color temp, since the RGB levels are at 100%. What have I done, and why would one calibration be better than another?

Thanks,

poormxdad

Bear,

I'm not sure how to ask it differently, but here goes...

Let's say I'm using HCFR and calibrate the RGB levels on my 5020. With Red at 500, Green at 500, and Blue at 500 (just for simplicity) HCFR tells me in Continuous Read mode that all the levels are at 100% at all percentages of Gray. I should have 6500k color temp. Soooooooooooooo, then I bump Green to 505, and chase Red and Blue till HCFR again tells me all the levels are at 100%. I should also read a 6500k color temp, since the RGB levels are at 100%. What have I done, and why would one calibration be better than another?

Thanks,


poormxdad


i would also like to know the answer to the above question.

Bear,

I'm not sure how to ask it differently, but here goes...

Let's say I'm using HCFR and calibrate the RGB levels on my 5020. With Red at 500, Green at 500, and Blue at 500 (just for simplicity) HCFR tells me in Continuous Read mode that all the levels are at 100% at all percentages of Gray. I should have 6500k color temp. Soooooooooooooo, then I bump Green to 505, and chase Red and Blue till HCFR again tells me all the levels are at 100%. I should also read a 6500k color temp, since the RGB levels are at 100%. What have I done, and why would one calibration be better than another?

Thanks,

poormxdad
Increasing one primary is the same as decreasing the other two. What you have more than likely done is essentially rebalanced your display at D65, but with greater light output. Assuming we are talking about a contrast (gain) control, rather than a brightness (bias) control, then you have also more than likely increased the contrast ratio (dynamic range) of the set, as well. You will need to double-check that something hasn't gone a-kilter with the usual visual patterns, though.

Bill

The replies are kind of dancing around the issue but there's something completely missing also...

In one example, somebody said "increase green" and referred to color temperature. If you do that, and the TV controls for green don't alter red or blue in any way (this will be true on some TVs, not true on other TVs), the color temperature will not change. That's why nobody should EVER be calibrating by color temperature. Most calibrators will use xy coordinates for grayscale calibration because all 3 colors are taken into account. If you only look at color temp, you are really only seeing the effects of red and blue while ignoring green.

There was another example where the settings were 500, 500, 500 and the question was... what happens if you change them all to 525, 525, 525... on most TVs, the image will be lighter with the higher settings. The color may or may not still be in balance - it depends on how the TV's controls work... some TVs are pretty linear and the controls only affect 1 color, but there are plenty of TVs where an adjustment to 1 color affects 1 or 2 other colors and moving all 3 settings the same amount may not move all 3 colors the same "amount."

If you are talking about the adjustments labeled low, offset, bias, etc. the RGB controls would work something like the brightness control if you moved all 3 colors up or down by the same amount so you don't want to be doing that - you start with the Brightness control set correctly and you have to keep checking the Brightness control to make sure your "low" adjustments haven't altered the effective brightness setting.

If you are talking about the controls labeled gain or high... moving those up/down together acts something like the Contrast/Picture control which wouldn't be quite as critical for most calibrations, but if you want 35 fL for your peak white level, adjusting the 3 gains up or down will move you off your 35 fL target (on most displays, there can be exceptions).

Remember that the white or shade of gray you are looking at for every grayscale step consists of about 71% green, 21% red, and 8% blue. So if you adjust the blue control, you won't get much change in luminance for that grayscale step - but if you adjust green - you can get a very large change in luminance for that step (which can alter gamma quite a bit - again, this varies from display to display). This is one reason that many calibrators minimize their changes to green - just makes the calibration easier with less touch-up and fewer back-and-forth iterations to get all the controls in balance. Certainly there are times when it makes sense to adjust green, and experience helps you determine when you should make a green adjustment or leave it alone and use the other colors.

Bear,

I'm not sure how to ask it differently, but here goes...

Let's say I'm using HCFR and calibrate the RGB levels on my 5020. With Red at 500, Green at 500, and Blue at 500 (just for simplicity) HCFR tells me in Continuous Read mode that all the levels are at 100% at all percentages of Gray. I should have 6500k color temp. Soooooooooooooo, then I bump Green to 505, and chase Red and Blue till HCFR again tells me all the levels are at 100%. I should also read a 6500k color temp, since the RGB levels are at 100%. What have I done, and why would one calibration be better than another?

Thanks,

poormxdad

Then all you've done basically is raise the contrast (white level). If you need to do that, use the contrast control instead, usually.

It's hard to know just what someone is asking, and as stated there can be numerous solutions......

When calibrating, you need to optimize the RGB levels. If I read the question right, if you max out RGB levels for driving the panel, you will have issues with color temp and probably with RGB gamma, and clipping.

As Chris mentioned, raising RGB levels is similar to increasing contrast. Settings need to be where the grayscale is most uniform (flat). Increasing contrast (too high) can have serious affect on this.

Alrighty then. Sooooooooooooo, I've read that for a plasma TV, I should be shooting for a luminance of 30-40ftL. Is there a more specific number for a Pioneer 5020 used mainly for movie viewing at night in a light-controlled room?

Let's say for sake of argument that the number is 35ftL. Is there also a general number for contrast for a Pioneer 5020 that I should be at to simultaneously reach 35ftL? I've been calibrating with contrast at 39. If I were to calibrate the RGB levels with contrast set at 39 and got 40 ftL max, should I reduce the RGB levels, or should I reduce contrast?

I haven't really had time to experiment with trying to reclaibrate using different RGB levels, BUT, if I did, would higher RGB levels across the board give me a higher or lower gamma?

Thanks,

poormxdad

Peak output is really not the primary concern. You calibrate for the tightest gray scale tracking and the smoothest response curve (gamma), with the transition to black that you want. The value that you get for peak output is what you get. You don't target that generally. You might change the output a few ftL and get a much better gray scale, or the gamma that you want. It really is not a high priority to hit a specific target.

Alrighty then. Sooooooooooooo, I've read that for a plasma TV, I should be shooting for a luminance of 30-40ftL. Is there a more specific number for a Pioneer 5020 used mainly for movie viewing at night in a light-controlled room?

Let's say for sake of argument that the number is 35ftL. Is there also a general number for contrast for a Pioneer 5020 that I should be at to simultaneously reach 35ftL? I've been calibrating with contrast at 39. If I were to calibrate the RGB levels with contrast set at 39 and got 40 ftL max, should I reduce the RGB levels, or should I reduce contrast?


Don't use the high/low controls instead of brightness/contrast.

If you use Movie mode, you're going to hit a limit as to what your peakw white level is anyway so why are you obsessing? 30 fL is ENOUGH - especially if you never see the TV output anything brighter. But humans must have some crow genes in them because they like bright shine-y colorful things and that (almost) always leads people to run TVs too bright and too colorful. I will confess to switching from 30 fL peak white levels to 35 fL even though I hate myself for doing so. It's like I caved to the dark side. All you are trying to do is find a level that doesn't cause eye-strain when you view the TV in a dark room - while avoiding having the level so high that you cause response problems (like 1 color running out of gas at 100% white and not being as bright as it needs to be to make 100% accurate).

Don't use the high/low controls instead of brightness/contrast.

If you use Movie mode, you're going to hit a limit as to what your peakw white level is anyway so why are you obsessing? 30 fL is ENOUGH - especially if you never see the TV output anything brighter. But humans must have some crow genes in them because they like bright shine-y colorful things and that (almost) always leads people to run TVs too bright and too colorful. I will confess to switching from 30 fL peak white levels to 35 fL even though I hate myself for doing so. It's like I caved to the dark side. All you are trying to do is find a level that doesn't cause eye-strain when you view the TV in a dark room - while avoiding having the level so high that you cause response problems (like 1 color running out of gas at 100% white and not being as bright as it needs to be to make 100% accurate).

Ditto for Pure mode on a PRO-151FD. I started out with Contrast at 38, (which seems to be everyone's number for the 151) and noticed with a flat grayscale from 30 to 90 that blue dropped about 5 percent at 100. I cut the Contrast to 37 and blue popped back up, to be even with red and green at 100. Of course, this is a small adjustment but still put out about 31 ft-lambert.

In ISF-Day mode, I couldn't believe how intense/bright you can get and not have one or more colors drop off. I set contrast to 34 and it still comes out to 41 ft-lamberts. In my controlled lighting environment, there is no need for any more light output.

I think the ultimate effect of getting high fL on displays is to trick the eye into better black levels. The more you can close the pupil, the less black detail you can see. I think this is especially useful in displays with poor contrast ratios. It's kind of like walking into a dark theater from outdoors, mid-day, you basically can't see your hand in front of your face for a brief period.

I get 36.something ftL with the contrast set at 39, brightness at 0 on my 5020. We hardly ever watch TV during the day, so the room is pretty dark. I have a small lamp behind the panel.

Just for the sake of increasing my understanding... Doug, you said you increased yours to 35ftL. If I wanted to drop to 35ftL, would I recalibrate with the contrast at 38, or just drop the contrast to the 38 (or 37) and retain the calibration I have now?

I suppose I am obsessing. But if we didn't obsess, who would become the professional calibrators, or their customers?

Thanks,

poormxdad

Yes, yo uare obsessing. You very well may louse up gray scale or gamma far more than the benefit of going from 36 to 35 ftL, whatever that might be. I suggest that if you obsess about anything, you do so about gray scale tracking, black level, and near black performance, all of which will make FAR more difference than peak white level in the quality of your image.

I get 36.something ftL with the contrast set at 39, brightness at 0 on my 5020. We hardly ever watch TV during the day, so the room is pretty dark. I have a small lamp behind the panel.

Just for the sake of increasing my understanding... Doug, you said you increased yours to 35ftL. If I wanted to drop to 35ftL, would I recalibrate with the contrast at 38, or just drop the contrast to the 38 (or 37) and retain the calibration I have now?

I suppose I am obsessing. But if we didn't obsess, who would become the professional calibrators, or their customers?

Thanks,

poormxdad

Unless you have a PROBLEM at 36 fL (one color can't get bright enough to make 100% accurate, for example), just leave it alone. The difference between 36 and 35 fL is nothing significant to your eyes. How much the grayscale is upset by a 1 fL change in peak white level varies a lot from TV to TV. I don't think you'll see much of a change, but you never know until the TV is measured after making the change.

If you are using a bias light, there's even less reason to change the peak white level - in fact with a bias light you can get away with a higher peak white level anyway. BUT... unless your bias light is 6500K (hate to use that term since it ignores green, but saying 0.3127, 0.329 for the d65 reference coordinates seems awkward), it is doing more to mess up your calibration than anything else you could be doing on your own. Incandescent lamps typically measure less than 3000K. Halogen lamps measure less than 4800K. So you really need to be using a light source close to 6500K for a bias light to be helpful. If you're not using that, you are destroying your calibration by flooding the room with light that is tinting all the colors you are trying to get right. www.cinemaquestinc.com (http://www.cinemaquestinc.com) sells "Ideal-Lume" bias lights for home and commercial/studio use and those are about as close to 6500K as you'll get without spending far more money. Their basic bias light is pretty affordable. THEN... if your walls/ceiling/floor are anything other than a neutral white or neutral gray, the color of the wall will mix with the bias light making even an accurate bias light become inaccurate. So you opened a whole new can of worms with the old light behind the TV trick - LOL! All that said... you don't absolutely HAVE to paint the walls/ceiling and change the floor covering - those are like the finishing touches (unless the walls, ceiling or floor are green - that's really bad and should be covered up ASAP). Getting a bias light that is close to 6500K is the #1 priority, even if the walls/ceiling/floor aren't absolutely neutral, the cooler bias light will help a lot with perceived image quality.

So just say D65, Doug. I really should not get started on the 6500K problem...see your own sig Leonard...

So just say D65, Doug. I really should not get started on the 6500K problem...see your own sig Leonard...

I would but the general enthusiast population doesn't "get" the distinction to a large extent. I find a large % all think d65, d6500, & 6500K are all the same thing.

Can you explain the difference for me, please....

I would but the general enthusiast population doesn't "get" the distinction to a large extent. I find a large % all think d65, d6500, & 6500K are all the same thing.

What's d6500? I know what the other two are, but have never heard of d6500.

What's d6500? I know what the other two are, but have never heard of d6500.6500K is a correlated color temperature
d6500 is nothing, just an incorrect term
D65 is a specific point, x=.3127, y=.329

Doug,

I have given serious thought to the "Ideal-Lume" lamp. My walls are painted a pale blue and I have dark blue carpeting--the room is more than the home theater. Will the Ideal-Lume lamp still help?

Thanks,

poormxdad

could I get my RGB levels to 100% each with more than one combination of RGB settings, say R 457, G 480, B 505 and R 488, G 496, B 552?

If both COULD have all three levels at 100%, would they both yield the same color temp (I think they would)? Would there be a difference in the picture, theoretically? Advantages to doing it one way or the other?

There are many grayscale combos that produce a fine flat scale. Normally you are looking for the brightest image so in that sense, there is only one correct RGB calibration:

#1. Increase each color on 100% white, while maintaining your grayscale balance, until you find the color that clips (where increasing that color produces no more increase in that color's output). [Find the clipped color]

#2. Adjust the other two colors to produce a proper RGB gray scale. [balance RGB]

Of course you will have to adjust the Contrast and Brightness controls and then repeat #1/#2 again (and again) until both the gray scale and Contrast/Brightness are properly set. [adjust Contrast and Brightness controls]

The color temperature will be correct if the RGB is neutral gray.

The picture will be as bright as possible once you find the clipped color.

The advantage of doing the steps outlined = the brightest possible image with a flat grayscale. Other RGBs work as well, they just won't be as bright.

There are many grayscale combos that produce a fine flat scale. Normally you are looking for the brightest image so in that sense, there is only one correct RGB calibration:

#1. Increase each color on 100% white, while maintaining your grayscale balance, until you find the color that clips (where increasing that color produces no more increase in that color's output). [Find the clipped color]

#2. Adjust the other two colors to produce a proper RGB gray scale. [balance RGB]

Of course you will have to adjust the Contrast and Brightness controls and then repeat #1/#2 again (and again) until both the gray scale and Contrast/Brightness are properly set. [adjust Contrast and Brightness controls]

The color temperature will be correct if the RGB is neutral gray.

The picture will be as bright as possible once you find the clipped color.

The advantage of doing the steps outlined = the brightest possible image with a flat grayscale. Other RGBs work as well, they just won't be as bright.

Unless the really bright version screws up your gamma, sometimes it's better to sacrafice 20-30cd/m^2 for better gamma response.

But I do agree with the general principle as a starting point for sure.

Unless the really bright version screws up your gamma, sometimes it's better to sacrafice 20-30cd/m^2 for better gamma response.

But I do agree with the general principle as a starting point for sure.

In general, the gamma is controlled by the allowed selections and to a more limited extent by the Contrast and Brightness. But, I agree that sometimes the brightest setting isn't the best for gamma and you have to turn the Contrast down a bit. In a good machine that shoudn't affect the gray scale much.

In general, the gamma is controlled by the allowed selections and to a more limited extent by the Contrast and Brightness. But, I agree that sometimes the brightest setting isn't the best for gamma and you have to turn the Contrast down a bit. In a good machine that shoudn't affect the gray scale much.

Yeah maybe I should've phrased that differently.

The gamma would be screwed up from the start, and lowering contrast get's it back to in the ball park.

And yeah not a top of the line display.

In general, the gamma is controlled by the allowed selections and to a more limited extent by the Contrast and Brightness. But, I agree that sometimes the brightest setting isn't the best for gamma and you have to turn the Contrast down a bit. In a good machine that shoudn't affect the gray scale much.

In practice, there can be a great deal of interaction between gamma, gray scale, brightness, and contrast adjustments. This varies with brands and models, and even within models, even in "good machines." It is simply hard to generalize the effects of the controls in many displays. When you get to the point in a calibration where you are getting that last little bit of accuracy in any of these parameters, changing one may affect any of the others in lots of cases.

Doug,

I have given serious thought to the "Ideal-Lume" lamp. My walls are painted a pale blue and I have dark blue carpeting--the room is more than the home theater. Will the Ideal-Lume lamp still help?

Thanks,

poormxdad

Yes, the Ideal-Lume lamp will still help. The farther the TV is from walls/ceiling/floor the better though. The dark carpet will reflect less light than a lighter carpet so that will help. It's not an ideal situation, but it would be much worse if the walls were yellow, green or red.

Doug,

I have given serious thought to the "Ideal-Lume" lamp. My walls are painted a pale blue and I have dark blue carpeting--the room is more than the home theater. Will the Ideal-Lume lamp still help?

Thanks,

poormxdad
The short answer is, yes. If you want to understand why, read the following: http://www.avsforum.com/avs-vb/showthread.php?t=1162578 .

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants Affiliate

"Advancing the art and science of electronic imaging"

George,

Good read.

Thanks,

poormxdad

Technicolor- NY can be added to the list of confirmed users. They placed a large order last week. Emulating professional practice yields better imaging.:)