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Author Topic: adust luminance with brightness or RGB sliders or both?  (Read 14575 times)
AFairley
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« on: December 18, 2009, 09:49:10 AM »
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I need to get my luminance to around 105 cd/m2 to match print brightness under display conditions (printer is profiled). I'm calibrating a Dell 2209WA with a Spyder 3 Elite (gamma 2.2, 6500K). The monitor factory defaults are brightness=75, R/G/B=100.

I found that if I calibrate leaving the RGB values near the factory default (say 93/96/94 after calibration), and lower the brightness to 10, I'm still way too bright, 140 cd/m2. I can hit the target by also lowering the RGB values together, though. (For example, to hit the luminance target my current calibtated settings are brightness 40, RGB 75/77/74, dap is 0.05.)

So my question is, should I calibrate by lowering brightness to 10 (or even lower) and going the rest of the way by lowering RGB; or doing it the way I am now setting brightness nearer the middle; or even leaving brightness up near the default and just lowering RGB values? Or does it make any difference in the end anyway?

Physically, what is the difference between the two types of adjustments? I believe lowering brightness just dims the backlight. What does lowering R or G or B do hardware-wise.

Thank you for shedding light!
« Last Edit: December 18, 2009, 12:21:58 PM by AFairley » Logged

Mark D Segal
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« Reply #1 on: December 18, 2009, 09:54:16 AM »
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Wnat software are you using with the Spyder 3? The software, if it is or works like Color Eyes Display does,  should give you a luminance calibration option which you would enter as the 105 cd/m2 you want, and it should return a value very close to that once the profiling is completed.
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Mark D Segal (formerly MarkDS)
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AFairley
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« Reply #2 on: December 18, 2009, 11:06:02 AM »
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Quote from: MarkDS
Wnat software are you using with the Spyder 3? The software, if it is or works like Color Eyes Display does, should give you a luminance calibration option which you would enter as the 105 cd/m2 you want, and it should return a value very close to that once the profiling is completed.

Mark, I am using teh Spyder 3 Elite software.  The way it works is that although you specifiy a target luminance, after doing the RGB calibration, the software gives you the luminance value and just prompts you to change it with the brightnesss slider on the monitor in an interative process.  Actually, since the RGB calibration screen also displays current luminance, you can use the cheaper Elite Pro software (which does not let you specify target luminance) to adjust luminance and save a few bucks.  With the Spyder Elite 3 software, I zero in on the luminance target at the same time I'm adjusting RGB values (also an interative process) to avoid any color shift as a result of changing brightness levels.

So my initial question remains....
« Last Edit: December 18, 2009, 11:45:42 AM by AFairley » Logged

Mark D Segal
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« Reply #3 on: December 18, 2009, 11:10:26 AM »
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In that case I can't be of further assistance because I'm not familiar with that inter-active process. With the software I'm using (ColorEyes Display) and I believe the same applies for BasicColor, one doesn't need to play with luminance interactively. Sorry.
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« Reply #4 on: December 18, 2009, 12:10:08 PM »
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I donít have a direct answer to the question. The vendor would probably be the best source.

As a suggestion, try setting it one way and perform some tests, then reset and retest. If you do, let us know the results.

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bjanes
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« Reply #5 on: December 18, 2009, 12:31:37 PM »
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Quote from: Justan
I donít have a direct answer to the question. The vendor would probably be the best source.

As a suggestion, try setting it one way and perform some tests, then reset and retest. If you do, let us know the results.

When I upgraded to 64 bit Win 7, I had to update my monitor calibration since the old solution did not work with the new OS. I had been using Pantone Optical with an old spider. In that system, one had to adjust the luminance with the control on the monitor. My new calibration software is ColorEyes and I was surprised that the software adjusted the luminance without my intervention.

An understanding of the calibration process would be helpful. I think that Color Eyes must adjust the luminance by manipulating the look up table in the video card. This might not be optimum since the video card is 8 bit and the luminance adjustment might take up a couple of those bits. It is for this reason that many users calibrate to the native white point of the monitor rather than a specific value such as 5000K or 6500K- that would also take up bits in the video card lookup table.

Some of the higher end displays have their own 10 bit lookup table in the monitor itself and adjustments in the monitor itself do not reduce the effective bit depth of the video card. I would think that adjusting the luminance with the monitor controls would be similar to the approach used by these higher end monitors. Does anyone have information here?

Bill
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« Reply #6 on: December 18, 2009, 12:39:29 PM »
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Quote from: bjanes
When I upgraded to 64 bit Win 7, I had to update my monitor calibration since the old solution did not work with the new OS. I had been using Pantone Optical with an old spider. In that system, one had to adjust the luminance with the control on the monitor. My new calibration software is ColorEyes and I was surprised that the software adjusted the luminance without my intervention.

An understanding of the calibration process would be helpful. I think that Color Eyes must adjust the luminance by manipulating the look up table in the video card. This might not be optimum since the video card is 8 bit and the luminance adjustment might take up a couple of those bits. It is for this reason that many users calibrate to the native white point of the monitor rather than a specific value such as 5000K or 6500K- that would also take up bits in the video card lookup table.

Some of the higher end displays have their own 10 bit lookup table in the monitor itself and adjustments in the monitor itself do not reduce the effective bit depth of the video card. I would think that adjusting the luminance with the monitor controls would be similar to the approach used by these higher end monitors. Does anyone have information here?

Bill

Bill, subject to correction, my understanding of the way ColorEyes works (and this is what I'm using) is that if the display allows it, calibration is performed in the display LUT itself; if the display does not allow it, the video card is used. Also, if one is fortunate enough to have a DDC-compliant display, one need not touch the display controls at all.
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Mark D Segal (formerly MarkDS)
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pherold
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« Reply #7 on: December 18, 2009, 12:39:42 PM »
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Yes, lowering the brightness dims the backlight.  

Lowering the RGB will affect the Liquid Crystal Diodes in the screen panel so that they will be partially obscuring the RGB colors in the panel at all times - even when displaying a full white.  The word around the industry is that it's asking a lot for an LCD crystal to not only do the normal light-blocking the produces the color variation on the screen, but also to include in that a precise amount of dimming like this.  You might expect a problem with uniformity across the display or see variation from day to day as you turn it on and warm it up.  Therefore, it's usually recommended that LCD's be calibrated with their RGB's at factory defaults, and let the video card handle the task of fine tuning the white balance, and the brightness if necessary.
The better displays with IPS (In Plane Switching) panels do a better job with this.  But with your Dell, you might look to see if you get the problems mentioned above.

As Mark noted, ColorEyes Display Pro is one of the few monitor calibration software packages that will include a brightness reduction in the video card if necessary in order to get your brightness down to your aimpoint.

We have an article on LCD's that pertains to this:
http://www.colorwiki.com/wiki/Monitors_Part_Two#Native_White

And another on the 'monitor-too-bright' issue:
http://www.colorwiki.com/wiki/My_Printer_I...UST_THE_DISPLAY
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AFairley
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« Reply #8 on: December 18, 2009, 01:19:50 PM »
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Thank you Patrick, that is precisely the information I was looking for, now I have a much better idea of how to proceed.  

Absent springing for a copy of the ColorEyes package, I am going to see if I can lower brightness in the ATI driver some before starting in on the calibration using the monitor hardware adjustments (though I'm not sure if or how the Spyder software interacts with the video card driver).

Thanks again.
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ChasP505
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« Reply #9 on: December 18, 2009, 01:31:23 PM »
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I have to comment on AFairley's method(s) with the Spyder3 Elite and the Dell 2209WA.  Several reviews of this popular entry level IPS paneled monitor report that merely lowering the Brightness control, all other settings at factory default, yields a luminance value of about 120cd/m2.  My experience with my own 2209WA and the Spyder3 Elite package confirmed this.

My monitor is approaching one year old and I now use the Spyder3 puck combined with ColorEyes Display Pro software.  Even though this monitor is "DDC enabled", typical of most Dell monitors, the DDC functionality doesn't work with CEDP.  So I manually lower the Brightness to 5% and leave all other monitor settings at defaults.  CEDP measures this as 115cd/m2 which seems to match perfectly with the ambient light level in my office.  CEDP also shows my RGB levels to be accurate at 100%, not requiring any adjustment.  The native white point of this display is about 6400K, but I use D65.

My prints match my display beautifully.  Of course I softproof in Photoshop and print with custom print profiles. The display is easy on the eyes, has good contrast with very good shadow detail. Banding is close to non-existant.
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Chas P.
AFairley
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« Reply #10 on: December 18, 2009, 01:36:53 PM »
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Quote from: ChasP505
So I manually lower the Brightness to 5% and leave all other monitor settings at defaults.

Thank you Chas, I was hesitant to go too low on the manual brighness adjustment because I had heard that on cheaper monitors over-lowering brighthness can lead to color shifts.  Sounds like that is not a problem for you.
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ChasP505
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« Reply #11 on: December 18, 2009, 01:52:59 PM »
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I don't have the budget at this time for a high end Eizo or NEC, so I need to get the best performance out of this entry level monitor that does not have an internal LUT.  I've read tons of discussions on how to calibrate low end LCD displays and after digesting all this info I accepted the philosophy that it's best to keep the display as close to its native/default settings as possible.  I also believe that if the monitor can only manage 120cd/m2 with the Brightness/Backlight lowered all the way to zero, it can only degrade the performance by trying to "force" it any lower. It just wasn't engineered to go to 105cd/m2.

My monitor is slightly less bright than when it was brand spanking new and I believe keeping the Brightness above 0% and not touching the Contrast or RGBs makes for a higher quality display profile.
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Chas P.
AFairley
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« Reply #12 on: December 18, 2009, 05:03:18 PM »
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So now I have another question.  What happens in the monitor when you adjust brightness by using the slider in the graphics card driver software as opposed to using the monitor's menu-driven settings?
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ChasP505
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« Reply #13 on: December 18, 2009, 05:15:12 PM »
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The difference is you're making a software adjustment at the video card, rather than making the only true physical adjustment on your display -- dimming the backlight.  Let's face it...  If you really need a monitor that can deliver 105cd/m2 or lower, you'll need to make a bigger investment.  Take a look at the NEC P221W.
« Last Edit: December 18, 2009, 05:21:26 PM by ChasP505 » Logged

Chas P.
bjanes
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« Reply #14 on: December 19, 2009, 06:23:39 AM »
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Quote from: MarkDS
Bill, subject to correction, my understanding of the way ColorEyes works (and this is what I'm using) is that if the display allows it, calibration is performed in the display LUT itself; if the display does not allow it, the video card is used. Also, if one is fortunate enough to have a DDC-compliant display, one need not touch the display controls at all.
Mark, yes, that is my understanding also. I do not have a DDC-compliant display nor does my monitor have its own LUT. On re-reading the documentation, I understand that one should do a precalibration procedure using the monitor's controls, e.g. to set luminance, so that this adjustment does not have to be made by ColorEyes using the video card LUT. I'm not sure if I did this correctly, and the precalibration option is no longer offered in the ColorEyes setup, presumably because it has already been done. To check this, do I have to uninstall the software and start over?

Bill
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ChasP505
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« Reply #15 on: December 19, 2009, 07:03:39 AM »
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Quote from: bjanes
...On re-reading the documentation, I understand that one should do a precalibration procedure using the monitor's controls, e.g. to set luminance, so that this adjustment does not have to be made by ColorEyes using the video card LUT. I'm not sure if I did this correctly, and the precalibration option is no longer offered in the ColorEyes setup, presumably because it has already been done. To check this, do I have to uninstall the software and start over?

Bill

Bill, This doesn't sound right.  Do you have "LCD Brightness/Gains" selected?  With this mode selected, there should be a selection available called "Monitor White" which is done before running the profiling.  It present your RGB and Brightness levels, which you adjust using the monitor's OSD controls.  My Dell 2209WA shows R 0, G 0, B -1.  Close enough that I don't make any OSD adjustments.  The Brightness level is based on whatever value you entered for white luminance.  I have 115cd/m2 entered and lowering the Brightness control to 5% zeros that adjustment out.

« Last Edit: December 19, 2009, 07:20:20 AM by ChasP505 » Logged

Chas P.
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« Reply #16 on: December 19, 2009, 07:35:46 AM »
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Bill and ChasP, yes, what ChasP shows above is what my version of the software (1.42) also shows, and the procedure described is correct - but tedious. Bill, check whether you also have this feature - I'd be surprised if a re-install were useful.
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Mark D Segal (formerly MarkDS)
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bjanes
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« Reply #17 on: December 19, 2009, 08:35:48 AM »
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Quote from: ChasP505
Bill, This doesn't sound right.  Do you have "LCD Brightness/Gains" selected?  With this mode selected, there should be a selection available called "Monitor White" which is done before running the profiling.  It present your RGB and Brightness levels, which you adjust using the monitor's OSD controls.  My Dell 2209WA shows R 0, G 0, B -1.  Close enough that I don't make any OSD adjustments.  The Brightness level is based on whatever value you entered for white luminance.  I have 115cd/m2 entered and lowering the Brightness control to 5% zeros that adjustment out.

Chas,

Thanks for the reply. Yes, I have LCD Brightness/Gains selected, but I don't know what that means nor can I find the explanation in the documentation. The setting was determined by ColorEyes and I did not over ride it. The solution to my pre-calibration was right under my nose. One simply clicks on the monitor white and the interactive screen pops up, and I get the display that you posted. I didn't see that image previously; did you update your post? Many thanks for the tip. My monitor apparently does not have  RGB settings, but little adjustment would have been needed, so this is not important. Against the advice of ColorEyes, I chose to use the native white of the monitor as suggested by Bruce Fraser and Chris Murphy in their color management book. I don't have a viewing booth and merely look at my prints under a Solux lamp situated about 1 foot from the print. This gives a luminance similar to the 110 cd/m^2 of my monitor. I allow my perception to adapt to the white of the Solux. 110 cd/m^2 is about 75% of the maximum luminance of my monitor, a Samsung SyncMaster 213T. This is not a very high end monitor, but my results are decent and I am in no rush to upgrade to possibly a NEC. For my purposes, I think the EIZOs are overkill and overpriced.
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bjanes
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« Reply #18 on: December 19, 2009, 08:40:01 AM »
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Quote from: MarkDS
Bill and ChasP, yes, what ChasP shows above is what my version of the software (1.42) also shows, and the procedure described is correct - but tedious. Bill, check whether you also have this feature - I'd be surprised if a re-install were useful.
Mark, you are correct. See my recent post to ChasP. It would be nice to have a DDC monitor with its own LUT so as to avoid this interactive process. However, if one's monitor is relatively stable, process does not need to be repeated very often.
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Mark D Segal
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« Reply #19 on: December 19, 2009, 08:53:28 AM »
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Fortunately that's true and if what you've got serves the purpose, you're in good shape. I also don't think it's necessary to go over the top on displays, but of course different folks have widely different views on this matter. I think in the range of several hundred up to around 1500 dollars there's significant bang to the buck for an up-grade depending on the model, but beyond that I'm not so convinced yet.
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Mark D Segal (formerly MarkDS)
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