Precision M6400 screen color as blue push/tint

Discussion in 'Dell Latitude, Vostro, and Precision' started by Sonnie Parker, Dec 15, 2008.

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  1. Dreamer

    Dreamer The Bad Boy

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    Very briefly, the color gamut is the range (not the amount) of colors that a display can reproduce and is determined by the backlight, which has nothing to do with the color depth (e.g. 6/8-bit per channel), the latter comes into play when we talk about color precision and accuracy.

    Standard notebook screens, found in 90% of notebooks, have about 45% NTCS color gamut due to the used CCFL backlight. For comparison, the typical desktop LCD CCFL backlight monitors/TVs have at least 72% NTSC color gamut, which is considered "standard" and then there is WCG-CCFL before we get to the W- and RGB-LED backlight.

    Higher color gamut, in terms of notebooks, could be achieved by using: DUAL LAMP CCFL, WHITE-LED, RGB-LED backlight

    The different backlight technologies have their pros and cons and their implementations could vary. Again, the used backlight technology itself isn't indicative for the display quality or accuracy, neither is the higher color gamut, the latter could only provide deeper/richer, more natural-looking colors, which could be a nice extra but the rest still mainly depends on the quality of the panel in front of the backlight, the color depth (incl. the quality of the dithering algorithm if used) etc.

    Now I'll stop here as you could easily find the answers of these type of questions by using Google, there is a number of guides covering this topic. Try these for starters:
    http://www.xbitlabs.com/articles/monitors/display/lcd-testmethods_2.html#sect1
    http://www.xbitlabs.com/articles/monitors/display/lcd-guide_11.html
    http://forums.anandtech.com/messageview.aspx?catid=31&threadid=1745344&enterthread=y
    http://www.lagom.nl/lcd-test/black.php#blacktest.png

    Another thing that I wanted to mention is that display specifications on manufacturer's sites should also be taken with a grain of salt when it comes to viewing angles, contrast ratio and even brightness, that's way we have sites such as these below that offer objective measurements for these parameters.
    http://www.notebookcheck.net/Reviews.55.0.html
    http://www.notebookjournal.de/ (use Google to translate if needed)


    Take care everyone.
     
  2. Mavtech

    Mavtech Notebook Enthusiast

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    In my case, WUXGA CCFL, even when I reduce the colors to 256 it dosent make a difference, I'm still seeing only one color in that chart (yellow) instead of the two colors (yellow and green) on the external monitor. Its the same as I described in my earlier post.
     
  3. robf23

    robf23 Notebook Guru

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    20 years in digital image production...

    You will never get monitors to 'a standard'. All you can do is get a profile to bend their deficiencies so you see as much of the gamut in a straight manner as possible. The only monitors that are going to be able to do this are monitors with a hardware gamut that completely covers the colour space your trying to work it. The best you can hope for is that the majority of colours and gamma and brightness on across a range of screens match. Then you can have fun matching that to a physical target, which again might shift the gamut out of some screens' gamut.

    You can't compare a screen against another because the other might be exaggerating what it's gamut in certain areas.

    It's the reason why high end CRT monitors used to cost £5000 and have hardware calibrators, not just profile building pucks. And it's the reason why no-one expects to do an serious retouching on a laptop with colours that change as you shift your head, and why everyone hangs onto their CRT's for their far superior colour stability as long as they can.

    LCD screens, even with LED are a long way off a high end CRT still. But the RGB LED screens do provide much wider gamut that at least addresses some of the older LCD limitations. That said, the viewing angles on my 5 year old LCD laptop are better than my new RGB LED sony...

    Serious colour accurate LCD screens even now are going to probably cost more than a heavily loaded M6400. Somewhere in the gamut, most LCD's have 'holes' where they are unable to display subtle differences in colour. Which is why we still have to check work done on our high end LCD monitors against a CRT, because there's times when those differences cant be seen.

    Realisticly, an LED is a better screen, once profiled and the software understands it, than an LCD... but it's not going to be a replacement for serious desktop kit in colour terms, and one does think that sometimes some don't understand fully what they are purchasing...

    Pretty much the only monitors i've seen have really good colour and calibration have been Barco References (£5000), Sony Artisans(£3000?), and lagging, but still better than the rest, Lacie Blue III (£2000) (the IV was a step down). Everything else is playing catch up by a long margin.

    You pay for what you get.
     
  4. puremind

    puremind Notebook Evangelist

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    I have tested the RGB LED foud on the Dell Studio XPS 16.

    The gamut is about 130% but there are some issues with the display:
    • Yes the colors do pop but green is widly oversaturated
    • Most colors have incorrect hue
    • Yes maximum luminance is very high but black levels are very poor, so the contrast remains only reaches 560:1
    • Color temperature is too high (greyscale suffers from a greenish tint)

    Those issues cannot be solved through calibration:
    1. Calibrating the greyscale to a different color temperature (65K standard) reduces the contrast significantly. Adding some red will fix color temperature but also increase black luminance and hence reduce the contrast.
    2. The color saturation and color hue controls do not alter the green color in any significant way.

    While the display may be ok for gamers who like nuclearly inaccurate colors, I wouldn't recommend it for photographers.

    Also remember that calibration wont't be able to fix the color temperature below 10% stimulous (greenish residual backlighting illumination remains).

    • The poor black levels mean the picture looks flat and 2 dimensional
    • The color inaccuracies lead to radiating grass and foliage as well as incorrect skin tones.


    I am including the details of my measurements below, as well as examples of how the color settings of the ATI Catalyst Control panel affect the readings. I also created color profiles using ColorEyes and BasicColor Display but because of the high color temperature, as expected, this leader to a poorer contrast.

    Contrast
    Black Level: 0,48cd/m²
    White Point (maximal luminance): 270cd/m²
    Contrast: 560:1

    Unfortunately, this is merely average, as most competing non LED panels have contrasts of 600:1 or higher. Also any good screen should have black levels below 0,3cd/m².


    Greyscale
    There is a blue and green excedent across the full luminance spectrum which increases at low stimulous. This is typically due to lower quality RGB LED backlighting. The backlighting produces a green/blue light instead of a white light, which becomes prominant at low LCD luminance. This means balancing the grey scale will require adding some red and black levels will suffer.

    [​IMG]
    [​IMG]


    The color temperature can be fixed however it means adding red, which further deteriorates black levels and contrast!


    Standard Color Space
    This is the color space with the standard saturation and hue setting

    Color Saturation = 100 and Color Hue = 0 (Standard)

    [​IMG]
    [​IMG]


    As demonstrated below, adjusting the color saturation and color hue controls in the AT Catalyst panel does not allow to correct the color inaccuracies!

    Increasing Color Saturation
    This merely removes blue from both the green and red primaries.

    Color Saturation = 120

    [​IMG]
    [​IMG]

    Color Saturation = 200 (Max)
    [​IMG]
    [​IMG]


    Decreasing Color Saturation
    This merely adds blue to both the green and red primaries

    Color Saturation = 60

    [​IMG]
    [​IMG]

    Color Saturation = 20

    [​IMG]
    [​IMG]


    Increasing Color Hue
    This merely adds blue to the red color.

    Color Hue = 30 (Max)

    [​IMG]
    [​IMG]

    Decreasing Color Hue
    This merely adds blue to the green color.

    Color Hue = -30 (Min)

    [​IMG]
    [​IMG]
     
  5. shlang

    shlang Notebook Enthusiast

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    Hi all.

    I managed to get access to DELL 2408WFP.
    Impressive... Good graphics.
    Gaming on it is bad, as monitor has noticable delay.

    I tried to match M6400 LGD018E to DELL 2408WFP "Desktop preset".

    I believe I got very close.


    I use loader which came with spyder 3 Elite. So provie gets applied on login to windows.

    The latest and I believe my best profile is here (next post):
    http://forum.notebookreview.com/attachment.php?attachmentid=30722&d=1234726225
     

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  6. shlang

    shlang Notebook Enthusiast

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    Tried to get max number of bits per color, while keeping colors in good match to DELL 2408WFP. Tried to compensate for Red tint which is bug of my spyder 3.

    Profile for R:G:B output 1.00:0.90:0.95 is attached. Please use external loader on this to load LUT on startup.
    Do not put this profile into color management for device!
    The profile is for LUT correction.

    To have correct colors 1. Adjust gamma as per attached picures. Apply for R, G, B. Thel use any available LUT loaders to load ICM profile and correct the LUT.

    Red gamma in the control panel must have center point adjusted to 0.46 output - this is to compensate for my spyder 3 problem with reds.

    My guess you should still have more than 14.2M colors after this correction. And it will display everything very very close to 2408WFP "Desktop" profile.

    Please let me know how it works for you if you try it.
     

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  7. Mavtech

    Mavtech Notebook Enthusiast

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    I'm selling my M6400 and have bought an HP 8730w as a replacement. But I just wanted to post some final images which illustrate how bad the problem was. My M6400 is WUXGA CCFL with the LG panel (LGD4C01). The external monitor used is a Dell 2007WFP.

    [​IMG]

    And this shows the problems it has displaying green CCFF00. It displays as yellow FFFF00 instead.
    [​IMG][​IMG]

    Test files used:
    http://img21.imageshack.us/img21/2260/color2j.jpg
    http://img18.imageshack.us/img18/743/ccff00andffff00onblack.gif
    http://img19.imageshack.us/img19/9417/ccff00onffff00.gif
     
  8. cindy-j

    cindy-j Newbie

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    I have a Dell M6400 also and have the same problem. The Dell rep I have talked to doesn't understand the problem.

    DUH

    Anyway, could Intoxicate e-mail the E2E-RGB-icm-Profil to me or make it so I could download it here to try? Maybe it would help I tried to download it here but it has the 10 download limit that has been reached already.

    Thanks I'm frusterated!:confused:
     
  9. mattgorringe

    mattgorringe Newbie

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    There seems to be a problem with color its like digital vibrance is turned up/ on on My Dell M6400 and but it cant be adjusted below 0. I have a dell M90 and the colors on that are much more natural. I have messed about with this for hours in the color manager . This has to be the most expensive non functional notebook I have ever bought. I can believe they shipped them like this.

    Does anyone have a fix for this or know of anything I can try? Im running the CCFL backlight version. Its as though i need to go negative on the Digital Vibrance setting.

    I just noticed on my M90 that if i set digital vibrance to 50 % i get exactly the same hideous colors as my M6400 set to 0% is there any hacks to make this value negative or over ride the nvidea setting. Or turn the vibrance feature off.

    No Amount of gamma tweaking seems to rectify this.
     
  10. Torht

    Torht Notebook Geek

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    Are people still having issue with calibrating the RGB LED screen for the M6400? Personally, I did not seem to have an issue while calibrating the matte RGB LED screen. When I tried to calibrate an E2E RGB LED screen, the results were decidedly greenish. Though, the matte one I calibrated was the Samsung screen, whereas the E2E one was LG. I assume it is not the glass that is causing the difference.
     
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