Adjusting LCD Monitor RGB Values Doesn't Reduce Number of Display Colors?

[bsteinagel]

I read some responses to a post on this forum regarding calibrating a Dell 2407WFP monitor.  I have the 2408WFP monitor and am confused by some of the responses that were left under that post.  Namely, one poster says that the lower you adjust your RGB values the less colors your monitor will display (I believe jani said that).  I was just talking with some of the color management gurus over at the Adobe forums and they say this is not true.  Adjusting the RGB values of a monitor adjusts the gain of the monitor.  This is like adjusting the volume of your stereo.  Just as you wouldn't listen to your music with the stereo turned all the way up because of distortion, etc.,  you're not going to get the optimum viewing experience with your monitor's RGB values set to 100.  In other words, by adjusting the RGB values, you're adjusting the strength of the colors, not the amount of colors the monitor can display.  

Furthermore, during the calibration process one of the steps involves adjusting the RGB values of your monitor to get a more accurate calibration.  Why would we be doing this as part of our calibration process if the very act of adjusting the RGB values would reduce the number of colors displayed by our monitors?  Seems counterproductive, does it not?

I was able to get a good calibration of my monitor by reducing my RGB levels to 70%, then fine tuning the levels during calibration in addition to lowering the brightness to 120 cd/m2.  I could not have lowered the brightness of my monitor enough to reach 120 cd with the RGB levels all the way at 100 using only the brightness control on my monitor.

If somebody can set the record straight and tell me if I'm misunderstanding something or misinterpreting it, it would be helpful.

Thanks,
Brad

[Henry Goh]

Brad,

That is how I calibrate my 2408 also.

I start with RGB values reduced to around 50% each.  Carry out the calibration according by setting target luminance at 120

[Czornyj]

I was just talking with some of the color management gurus over at the Adobe forums and they say this is not true.  Adjusting the RGB values of a monitor adjusts the gain of the monitor.

That's absolutely not true! You could only adjust the gain in high end, CRT monitors like Barco Reference, or Sony Artisan. A normal LCD panel has a simple, white CCFL backlight, so you can't change the gain of RGB channels! You can adjust the "gain" only by cutting the brightness of R,G and B pixels of the LCD matrix, and when the internal LUT and matrix of the panel have 8 bit control, you're also cutting the available palette as well. Some panels for color-critical applications (Nec 90 series, Eizo CG, Quato IntelliProof, LaCie) have 12-14 bit LUT and 10 bit matrix control, so you're not loosing color tones when calibrating the white point (only the luminance is lowered). The only panels that have real "gain adjustment" are RGB LED backlight LCD's.

[jani]

The only panels that have real "gain adjustment" are RGB LED backlight LCD's.

And even so, it's not for certain that all LCD panels with LED backlight may be adjusted in that manner.

But as Brightside's technology makes it into more and more panels, and possibly with the advent of OLED and other exciting new technologies, the shrinking color space problem may be reduced.

For regular LCD monitor calibration, configure your hardware calibrator for an LCD panel, and its software will provide instructions for LCD adjustment (brightness) and make the necessary adjustments to the colour look-up table.

[bsteinagel]

For regular LCD monitor calibration, configure your hardware calibrator for an LCD panel, and its software will provide instructions for LCD adjustment (brightness) and make the necessary adjustments to the colour look-up table.

That's the problem.  The Eye On Match software for my i1 Display 2 colorimeter doesn't seem to do that.  It tells me to reduce the brightness down to the target value using the brightness control on my monitor, but it won't try and adjust the video card LUT to reach the target luminance if adjusting the monitor's brightness isn't enough.  Even with the brightness set all the way to 0 I still cant get my display below 140 cd/m2 or thereabouts.  I'm trying to get it to the recommended target luminance value of 120 cd.  The only way to do this is to lower the RGB values individually to 70 before calibrating.

Am I reducing the number of colors my display can show by doing this?  If so, any suggestions on how to work around this?

Thanks,
Brad

[Czornyj]

Am I reducing the number of colors my display can show by doing this?  If so, any suggestions on how to work around this?

Yes - you are reducing the number of colors of your display, and the contrast. There's no work around for this - (eventually you may set the panel to 100% brightness and leave it for a few months till CCFL will burn out a bit)

On the other hand - 140cd/m^2 is not that bad

[jani]

That's the problem.  The Eye On Match software for my i1 Display 2 colorimeter doesn't seem to do that.  It tells me to reduce the brightness down to the target value using the brightness control on my monitor, but it won't try and adjust the video card LUT to reach the target luminance if adjusting the monitor's brightness isn't enough.  Even with the brightness set all the way to 0 I still cant get my display below 140 cd/m2 or thereabouts.  I'm trying to get it to the recommended target luminance value of 120 cd.  The only way to do this is to lower the RGB values individually to 70 before calibrating.

Am I reducing the number of colors my display can show by doing this?  If so, any suggestions on how to work around this

As Czornyj writes, yes, you are.

This is unavoidable when you try to force a bright display to behave like a not-so-bright display, and it was the basis of my major disappointment with the Dell 2405.

[The View]

I've had the same questions when I adjusted my old, brighter LCD.

What I learned is, that adjusting the card LUT is NOT recommended and you will lose color.

[jani]

I've had the same questions when I adjusted my old, brighter LCD.

What I learned is, that adjusting the card LUT is NOT recommended and you will lose color.

If you don't let your calibration software adjust the LUT, then you won't get a calibrated device. Sorry, there is no complete win-win solution for such displays.

You can win if you have more advanced displays, though.

[The View]

If you don't let your calibration software adjust the LUT, then you won't get a calibrated device. Sorry, there is no complete win-win solution for such displays.

You can win if you have more advanced displays, though.

Those advanced displays...

... like the Eizo ColorEdge?

Any other members of the club? How's the Apple Cinema Display doing? (not a member, I suppose).

[Czornyj]

Those advanced displays...

... like the Eizo ColorEdge?

Any other members of the club? How's the Apple Cinema Display doing? (not a member, I suppose).

Like I said - Nec x90 series, Eizo CG, LaCie, Quato. They have 12-14 bit, programmable LUT, so the automatic hardware calibration is possible. Plus they have proper brigtness control, and you can calibrate them to lower luminance level without any problem. I can even get 20cd/m^2 on my 2190UXi.

[Czornyj]

Like I said - Nec x90 series, Eizo CG, LaCie, Quato. They have 12-14 bit, programmable LUT, so the automatic hardware calibration is possible. Plus they have proper brigtness control, so you can calibrate them to lower luminance level without any problem. I can even get 20cd/m^2 on my 2190UXi.