Hardware Profiling a Laptop LCD - Impossible?

Rishi Sanyal , Mar 11, 2007; 03:52 p.m.

This is regarding a consistent blue-->violet hue shift I get in all color-managed (CM) applications after hardware profiling my MacBook Pro (MBP) LCD.

I use an i1 colorimeter + Eye-One Match 3.6 software.

I've successfully calibrated, using the above package, my Sony CRT & a 20" Apple Cinema Display. Here are there profiles mapped against the sRGB color space & against each other:

I then tried calibrating my MBP LCD, as did a fellow named Andrew on another forum, and we both keep getting these squarish (indicating a limited gamut) 3D plots of our calibrated profiles, which you can see here ('i1-calibrated LCD' profiles are the profiles generated from my own calibration of my MBP LCD using the i1 colorimeter; 'Color LCD' is the original canned profile for the MBP LCD provided by Apple):

It's not the limited gamut that bothers me. It's the blue portion of the monitor gamuts that, as measured by the i1 colorimeter/software, lies *outside* the sRGB gamut.

When using these i1-generated monitor profiles, blues turn lighter, and somewhat violet, in CM applications for both Andrew & I.

Let me see if I can replicate this for you, below. Please use a color-managed browser (Safari); or, if you're a Windows user, please download the files via the links I've provided, and then view them in a color-managed application. If you just don't have access to a CM app, then, for you I have included the third image below, where I have converted my monitor capture of the blue square to the sRGB profile.

Here's pure blue in the sRGB color profile (0,0,255)
[a.k.a. What I SHOULD see as blue]:

Linked Here

Here's a screen capture of this same exact file as viewed on my MBP LCD (i1-generated ICC profile embedded)
[a.k.a. What *I* DO see as blue, IF *YOU* are viewing in a CM app]:

Linked Here

Here's the above file (screen capture) converted to sRGB
[a.k.a. What *I* DO see as blue, IF *YOU* are vieweing in a nonCM app such as IE or Firefox]
[meaning for you Safari/CM viewers out there, this & the above square should look the same]:

Linked Here

As you can (hopefully) see, blues get lighter when viewed in CM applications on my MBP LCD. A slight violet hue is also introduced into blues, as can be seen here (exaggerated below, intentionally, by angling the laptop screen at a non-standard viewing angle):

The square on the left (that appears purple/violet) is actually (0,0,255) in a sRGB document in Photoshop (color-managed, obviously). The square on the right is (0,0,255) in a ProPhoto RGB document in Photoshop. For some reason, if you create a new ProPhoto RGB or ROMM-RGB document and dump (0,0,255) paint in it, the color remains blue even when using my i1-generated monitor profile. Create the document in any other color space, dump blue paint, and you get the hue shift I've been mentioning.

To further analyze where this hue shift is arising from, I took both the blue/sRGB & blue/ProPhoto RGB documents in PS, and 'Converted to' my i1-generated monitor profile (since, essentially, this is what PS is always doing on the fly as a CM application). Here's what I got:

sRGB to monitor profile: (0,0,255) --> (102,0,255)
ProPhoto RGB to monitor profile: (0,0,255) --> (0,0,255)

For the blue in the sRGB document, the red channel was increased from 0 to 102! Hence the hue shift to violet. Not so for the blue in the ProPhoto RGB document.

I also performed this experiment with my other i1-generated monitor profiles; that is, converting the (0,0,255) blue in my sRGB document to the following monitor profiles:

Conversion to MBP LCD profile: (0,0,255) --> (102,0,255)
Conversion to ACD LCD profile: (0,0,255) --> (55,0,249)
Conversion to Sony CRT profile: (0,0,255) --> (16,0,255)

As you can see, the violet hues being introduced to blues for Andrew and I are coming from the introduction of reds as Photoshop converts to our monitor profiles on-the-fly. This violet hue is much less noticeable on the ACD, and almost completely unnoticeable on the Sony CRT. Makes sense, given the values above, right? On the MBP, a 0% red in a pure blue image is being changed to 40% red before output to monitor, resulting in the hue shift to violet. On the ACD, a 0% red in a pure blue image is being changed 21% red before output to monitor, resulting in a slight hue shift to violet. On my Sony CRT, 0% red in a pure blue image is being changed to 6% red before output to monitor, essentially allowing pure blues to remain pure blue on the monitor.

So, why the seemingly bad monitor profiles being generated by i1 for our MBP LCDs? Another user on the Luminous Landscape forum had this same sort of squarish monitor profile with an overextended gamut in the blues that lay outside the gamut of sRGB when he profiled his Pismo Powerbook years ago using the i1 colorimeter... see profiles here:

Note, the 'canned' monitor profiles provided by Apple do not have this overextended gamut in the blues, and also do not display this hue shift with blues. However, the canned Apple profiles are rather inaccurate in other regards (e.g. there's no way the gamut of our displays is almost as wide as sRGB or as that of the iMac display)... I had crazy over-saturated reds/oranges on my MBP using the canned Apple profile... hence, I am mostly happy with the i1 calibration... except for the entirely inaccurate blues in CM apps. Yes, blues remain blue in nonCM applications, since nonCM apps just throw the (0,0,255) values at my screen rather than first converting them to (102,0,255)... which is just insane!

Any help would be greatly appreciated, as none of us have solved this problem thus far...

Thanks in advance,
Rishi

P.S. We calibrate in total darkness, with native white point and gamma set to 2.2. LCD panels are positioned as normal to the table surface as possible, so that colorimeter does not exert any significant force on the LCD due to its weight. Luminance is usually set between 90-120 cd/m2, but it doesn't really matter: I've tried every combination of 90, 100, 120 cd/m2 with every possible combination of native white point/D65 & gamma 1.8, 2.2... you name it, I've tried it, and still I get this ridiculous behavior with blues...

Responses

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Ellis Vener , Mar 11, 2007; 04:07 p.m.

"{It's not the limited gamut that bothers me. It's the blue portion of the monitor gamuts that, as measured by the i1 colorimeter/software, lies *outside* the sRGB gamut."

So? Use a bigger colorspace than sRGB.

Rishi Sanyal , Mar 11, 2007; 05:16 p.m.

That's not the point.

I'm simply stating that I think it's *strange* that my laptop LCD's monitor gamut falls outside of sRGB, and I'm *wondering* if that's part of the explanation for why blues shift to violet.

I solely work in ProPhoto RGB. But that doesn't change the fact that most people still post images in sRGB and my digital camera probably also uses some variant of the sRGB color space or Adobe RGB and my film scanner... well that's another long story.

The *only* cases where blue stays blue is when I create a document in PS in the ProPhoto RGB or ROMM-RGB color spaces (yes, that's right, I tried creating a blue document in *every other profile* that exists in Photoshop). Pure blue in *every other* color space shifts hues. And I imagine that the only reason pure blues (RGB = 0,0,255) stay blue for documents in the ProPhoto RGB or ROMM-RGB color spaces is because the blue primaries for these color spaces are 'imaginary'. Hence, for some reason I don't pretend to understand, application of the monitor profile converts this 'imaginary' blue to a pure 0,0,255 blue, rather than a violet 102,0,255.

The main point here is that blues in pretty much every image become lighter and shift hues in CM apps.

Roger Smith , Mar 11, 2007; 07:00 p.m.

" I tried creating a blue document in *every other profile* that exists in Photoshop). Pure blue in *every other* color space shifts hues. "

Hmm, that's really interesting. I wonder if Andrew Rodney or someone can comment on this.

I created a blue square in Photoshop (0, 0, 255 with fill bucket) and then went to "assign profile" and went through the list. SRGB, EktaSpace, ProPhoto and AdobeRGB all looked quite "blue." My monitor profile also looked blue- pretty much identical to adobeRGB. I then assigned blue to SRGB and then looked and "conversion" to Adobe, ProPhoto, etc, and all retained their blueness. I'm using a hardware calibrated CRT.

Your film scanner ought to be able to give you files in ProPhoto.

It sounds to me like your screen may not be currently able to accurately display blues. In the Eye-One software advanced settings there is the option of doing a look-up table and I think that's recommended for LCDs rather than the default RGB curves. Did you try the different profiles and see if it made a difference?

Rishi Sanyal , Mar 11, 2007; 06:51 p.m.

Hi Roger, so we meet again... good to hear from you :)

I'm not surprised that you don't see this hue shift... neither do I on my hardware calibrated CRT.

Re: my monitor not being able to accurately display blues... I highly doubt that. In fact, blues are the one thing this monitor seems to have a very high response in. Add to that the fact that in a nonCM application, the blue sRGB file looks (to my eye) perfect. And by perfect I mean it looks pretty much exactly like the blue sRGB file in BOTH CM & nonCM applications on my hardware calibrated Sony CRT.

So my MBP LCD is quite capable of producing that true blue that I see on my CRT... only when my i1-generated monitor profile isn't mucking up the blues by adding all that red...

Re: Advanced settings in Eye-One for 'doing a look-up table'... Is that under 'Preferences' in the Eye-Match software? Because I didn't see any such option when I went through the 'Advanced' calibration...

L G , Mar 11, 2007; 09:12 p.m.

The profile for my Macbook pro has a much smaller gamut than the Dell 3007WFP that I use as an external monitor with it. The only area that the Macbook LCD has a wider gamut is in a very narrow range of blue. Both were calibrated with an i1 Display.

I see no problems displaying blues on the Macbook, but the color is noticeably poor compared to other monitors.

I don't understand how you got the screen captures. Does the mac capture the profile altered data?

Rishi Sanyal , Mar 11, 2007; 08:32 p.m.

L G,

Yes, the Mac does capture the profile altered data. It's the same thing as loading a pure blue (0,0,255) sRGB image in Photoshop, and then 'Converting to' the i1-generated monitor profile.

Sounds like the profile for your MBP LCD matches up with mine. Please check your i1-generated profile in ColorSync Utility, and confirm.

Given your post, I'm willing to bet you a nickel, maybe even a dime, that the three blue squares in this post all look about the same (the last, sRGB, one might be a little lighter) color in Safari, but that none of them look AS blue (as in neon-like pure blue) as the first square *as displayed by Firefox* on your MBP LCD. (In Firefox: I predict that for you the second square will be a little more violet, and the third one will be a lighter blue than the first square).

Am I correct?

Serge Cashman , Mar 11, 2007; 08:50 p.m.

How does a profile look like for a monitor at it's native state (Native/Native)?

I would have thought it's an i-1 issue if Andrew over at LL wasn't using Spyder2 Pro and Basiccolor. There could be some videocard LUT weirdness happening that isn't measured correctly.

Rishi Sanyal , Mar 11, 2007; 10:08 p.m.

Serge,

Andrew also tried the DTP94, and got similar results.

I tried clearing the LUTs using the 'ProfileMenu' utility that was suggested to you over at LL. I also tried Tim's method of first, before calibrating, setting a standard profile (such as sRGB) as your monitor profile instead of a 'canned' profile made from information downloaded from an EDID chip on the monitor. And then calibrating.

No luck.

Native/Native calibration put a very offensive blue cast over my entire screen in general (hence my shying away from it), yet STILL somehow caused CM apps to exhibit this blue-->violet hue shift.

Thanks to everyone for trying to attack this strange issue... Agree with Roger -- a comment from a seasoned expert might be very helpful at this point... i.e. on a very basic level, what would prompt a color-management module (CMM) such as the Adobe CMM or Apple CMM to throw in 40% (102 out of 255) red to a pure blue tone before throwing out to the monitor?

In other words, what exactly in a device color profile (specifically, monitor profile) would instruct a CMM to add 40% red to a pure blue tone to try and approximate 'pure blue'?? Sounds like insanity to me, but please correct me if I'm wrong!

L G , Mar 11, 2007; 09:09 p.m.

Using color sync my profile looks very close to yours.

Using safari the last two blues look the same. The first one looks like the firefox first one. It is darker blue than the other two, but not as intense as when displayed on the Dell LCD.

You are right about how they look in Firefox.

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