What is Native White Point versus D65? - AVS Forum
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post #1 of 16 Old 01-09-2014, 11:47 AM - Thread Starter
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I've purchased an i1 Display Pro colorimeter and I'm working on calibrating my PC monitors.

However, when I start the application, it gives me a choice of target White Points. After reading some articles online, it seems like the two common choices are "D65" (6500K) and "Native".

However, what does "Native" White Point mean?

I've used the i1 Display Pro's Profiler application for Windows, and when I select "Native", it achieves a white point of around 7500K but if I select 6500K then it does achieve around 6500K.

What's going on here?

To further complicate matters, my monitor has built-in color temperatures to choose from...
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post #2 of 16 Old 01-09-2014, 12:04 PM
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I don't know what you're doing but when I last looked... Native has nothing to do with colour temperature but contrast ratio.

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post #3 of 16 Old 01-09-2014, 12:33 PM
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Native doesn't calibrate the white point, but uses the color of the monitor as is.

This maximizes the number of bits the ICC profile has to play with, but most ICC implementations are relative colormetric. So while the ICC profile will apply some correction, it won't be as absolutely accurate as calibrating the whitepoint via the 1D-LUT. But on a lowend monitor that has a really blue white point, you can throw away 1/3rd of your bits trying to shift it back to D65, this can cause banding and other artifacts that may be more objectionable than the relative colormetric match.

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post #4 of 16 Old 01-09-2014, 01:06 PM
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How would you make an Apple display (metal frame) really accurate then? All you can adjust on those displays is the brightness. There's nothing else you can play with.

Though, I haven't seen any banding...
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post #5 of 16 Old 01-09-2014, 01:15 PM
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Perhaps i1profiler can access and adjust monitor's LUT? Have you tried ticking on AGC although I think it's good for brightness/contrast control only...
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post #6 of 16 Old 01-09-2014, 01:23 PM
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Originally Posted by xvfx View Post

How would you make an Apple display (metal frame) really accurate then? All you can adjust on those displays is the brightness. There's nothing else you can play with.

Though, I haven't seen any banding...

Aside from apple, who ever said they were?

The ICC profiles from Apple for those monitors do include a vcgt tag which apple uses to apply a 1D LUT to get the monitors to D65.

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post #7 of 16 Old 01-09-2014, 01:23 PM
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Originally Posted by mytbyte View Post

Perhaps i1profiler can access and adjust monitor's LUT? Have you tried ticking on AGC although I think it's good for brightness/contrast control only...

The LUT is in the video card and controlled by the OS.

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post #8 of 16 Old 01-09-2014, 01:36 PM
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Quote:
Originally Posted by sotti View Post

Aside from apple, who ever said they were?

The ICC profiles from Apple for those monitors do include a vcgt tag which apple uses to apply a 1D LUT to get the monitors to D65.
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So while the ICC profile will apply some correction, it won't be as absolutely accurate as calibrating the whitepoint via the 1D-LUT.

I mean with x-rites. Not Apple's ICC's. They're terribly off. As I used table based and large patch set.

As this LUT stuff is way beyond me.
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post #9 of 16 Old 01-09-2014, 01:44 PM - Thread Starter
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Thanks for the information!

Do I understand this correctly then...?

There are two options for calibration:

1) Adjusting monitor's LUT tables - This is adjusting the monitor's RGB controls and temperature when trying to calibrate to D65, etc.
2) Not adjusting LUT tables - This is when you leave the monitor at "default" settings and you use an ICC/ICM profile to correct any colors.

Furthermore, do I understand it correctly that there are two LUT tables? One on the monitor (adjusting RGB using the physical buttons on the monitor or DDC commands) and one in the video card (loaded using ICC/ICM profile).
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post #10 of 16 Old 01-09-2014, 01:46 PM
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Quote:
Originally Posted by xvfx View Post


I mean with x-rites. Not Apple's ICC's. They're terribly off. As I used table based and large patch set.

As this LUT stuff is way beyond me.

Xrite does add a vcgt tag to their ICC's. If it's not as accurate as CalMAN, that has a lot to do with the process and time we've spend developing our AutoCal algorithm.
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So while the ICC profile will apply some correction, it won't be as absolutely accurate as calibrating the whitepoint via the 1D-LUT.

As this LUT stuff is way beyond me.

Using alternative settings are usually for people who know why they want those options.

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post #11 of 16 Old 01-09-2014, 01:51 PM
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Quote:
Originally Posted by sofakng View Post

Thanks for the information!

Do I understand this correctly then...?

There are two options for calibration:

1) Adjusting monitor's LUT tables - This is adjusting the monitor's RGB controls and temperature when trying to calibrate to D65, etc.
2) Not adjusting LUT tables - This is when you leave the monitor at "default" settings and you use an ICC/ICM profile to correct any colors.
Correct, but ICC correction may be a relative match to the white point, or an absolute ICC match, so you won't necessarily get D65 for white if you go with option 2.
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Originally Posted by sofakng View Post

Furthermore, do I understand it correctly that there are two LUT tables? One on the monitor (adjusting RGB using the physical buttons on the monitor or DDC commands) and one in the video card (loaded using ICC/ICM profile).
Yes/no, depending on the monitor. A few monitors do have 1D LUTs, but the majority of the monitors just have a custom white point, some also have cuts. So you can calibrate the white point for the monitor with the gains, and then calibrate the 1D LUT to make sure the white point is consistent from 0% to 100% and the gamma is also on target.

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post #12 of 16 Old 01-09-2014, 01:53 PM
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Originally Posted by sotti View Post

Xrite does add a vcgt tag to their ICC's. If it's not as accurate as CalMAN, that has a lot to do with the process and time we've spend developing our AutoCal algorithm.

I must next look into investing for that. For both computers and TV's.
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post #13 of 16 Old 01-09-2014, 01:56 PM - Thread Starter
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I'm terribly sorry but I'm still a bit confused.

Is it OK to adjust the white point on your monitor using the built-in RGB controls? (or DDC commands)

If I'm understanding correctly, you shouldn't adjust anything on the monitor and just use ICC profiles? (Is an ICC profile where the video card 1D-LUT is stored?)
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post #14 of 16 Old 01-09-2014, 02:36 PM
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Quote:
Originally Posted by sofakng View Post

I'm terribly sorry but I'm still a bit confused.

Is it OK to adjust the white point on your monitor using the built-in RGB controls? (or DDC commands)

If I'm understanding correctly, you shouldn't adjust anything on the monitor and just use ICC profiles? (Is an ICC profile where the video card 1D-LUT is stored?)

The issue with all of this is bit-depth. Since the DVI/Displayport cable is only going to carry 8-bit data and the OS only has an 8-bit frame buffer the more correction you have to do in the computer the few bits you can use to send to the monitor.

So do as much calibration as possible in the monitor hardware. This will mean you will have fewer corrections to make on the other side of the cable. Doing the remainder grayscale calibration with the 1D LUT in the graphics card will then preserve as much bit depth for the OS. With all calibration you want to start as close to the screen as possible and then work your way backwards towards the source.

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post #15 of 16 Old 01-09-2014, 03:12 PM
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Here's a post I wrote on HardForum about LUT adjustments and banding. I think I'm on the right track, but not 100% sure, so keep that in mind.
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post #16 of 16 Old 01-11-2014, 03:15 PM
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To be clear, an external LUT box wouldn't solve the issue of banding, right?
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