Way too accurate CRT gamma calibration targets available

Discussion in 'Photoshop Tutorials' started by Timo Autiokari, Jul 20, 2003.

  1. Hi,

    I've uploaded a set of unbearably accurate CRT gamma calibration charts:
    http://www.aim-dtp.net/aim/evaluation/gammaspace/index.htm
    Please have a look at them, I hope to hear if there is something to improve
    still.

    The above is in form of CRT gamma evaluation but you can right-click the
    chart (of the system gamma-space that you are calibrating to) and make the
    chart as the background image of your desktop, there it will help
    AdobeGamma calibration enormously.

    These chart are unbearably accurate since, with most consumer grade
    monitor, they make the small drift in the operation point of the monitor
    detectable. This drift can be rather rapid so that a change is detected
    within a hour or two or it can be very slow so that a change is detected
    only after some 8 to 24 hours of power on time.

    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 20, 2003
    #1
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  2. Timo Autiokari

    Stephan Guest

    Yes you set the size of your naviagation frame properly.
    Now that is funny as shit! Why would anyone want to get them then if they
    are unbearable?
    You have been explaining us for a long time why Adobe is wrong and why you
    are right, Why our monitors are all displaying wrong colors and yours is
    not,
    yet, I am still waiting to see ANYTHING you have created with your superior
    settings and deep understanding of profiles etc.
    You are like a guy in a painting group telling people why the camel hair
    molecular structure is far superior to nylon.
    Frankly, just between you and me, I don't give a shit.Abobe Gamma and my
    Epson are my friends and my work looks good.
    I see you on a soap box with a sign around your neck saying : ASJUST YOUR
    MONITORS NOW! THE END IS NEAR

    Stephan
     
    Stephan, Jul 20, 2003
    #2
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  3. Timo Autiokari

    °¿° Guest

    How near?
     
    °¿°, Jul 21, 2003
    #3
  4. Thanks for the contribution.

    It might be helpful to note above and/or below the RGB/YMC "bars" (in a
    small font) with which gamma control it should be adjusted, and in what
    direction (e.g. +R or -G) to reach a balance.

    Bart
     
    Bart van der Wolf, Jul 21, 2003
    #4
  5. Timo Autiokari

    JSH Guest

    Timo, your new site is BRILLIANT. My monitor has never been as well
    calibrated and for the first time in years I am getting accurate prints from
    my Epson. So from one user a heartfelt thanks.

    Incidentally, I don't know who Stephan is but he seems both ill-mannered and
    juvenile. His language range is also a little lacking. Perhaps he will
    learn some original words one day, though sadly it seems to me that a whole
    generation of Americans seem to think that the word shit can be used to
    describe anything. The English language has so many wonderful words it is
    sad that they over-use this one, rather ugly one. But let's all hope that
    little Stephan learns some new ones soon, shall we? I'm sure when he does
    his doting parents will be so proud of him. He might then also get a
    girlfriend or boyfriend and go out more and bother all of us a little less.

    Hang on though. Stephan is clearly very intelligent, or at least he seems
    to think so. I wonder.... is he really Stephen Hawking, Newton Professor of
    Physics at Cambridge, authir of a Brief History of Time. Silly of me not to
    see it straight away, and not to realize that the spelling of Stephan was
    not a first grade spelling mistake but a ruse to mislead us all.
     
    JSH, Jul 21, 2003
    #5
  6. Timo Autiokari

    SalsaMaster Guest

    The sign I saw in downtown Seattle this past Friday said that the end was
    just around the corner. So I walked around the corner, saw a Starbucks and
    stopped in for a cup of their house blend. Did you know that you can't walk
    a block in downtown Seattle without seeing a Starbucks... Anyway, I then
    went up REI and checked out their tents (I'm trying to get my pack weight
    down) then went down to the market and picked up some fresh fish for dinner.
    I must've walked around a hundred corners and never did see the end. <g>
    Maybe we already missed it ?
     
    SalsaMaster, Jul 21, 2003
    #6
  7. Timo Autiokari

    Stephan Guest

    English happens to be my third language.
    My real name is Stephane but since most people can't read properly they
    assume it is Stephanie because of the E at the end.
    I read Hawking and you should use you spell check, he is an author, not an
    authir.
    Thanks you for assuming I am so young, it is refreshing.
    There are a few more words I know and I would like whisper them in your hear
    but I let you guess them, more fun like that

    Stephan
     
    Stephan, Jul 21, 2003
    #7
  8. Timo Autiokari

    openmind Guest

    Timo, thanks for posting this. English not being your native tongue, you
    did a great job. Here are a few suggestions for improvement. The phrases
    in quotes are from your page.

    "Set as Backgound" - in the Netscape browser, I believe that this should
    be Set as Wallpaper.

    "On the left left" - change to At the far left?

    "Top left" - Top right?

    It would also be nice to have a "hard wired" chart that shows how a
    monitor is NOT properly calibrated. This chart will show how badly the
    far left, center and right sections look like.

    My top and bottom right look pitch black and I have no idea what you
    meant by stripes. Yes, this tells me I need to adjust the monitor's
    black point setting.

    My far left and center are almost gray. But compared to the chart's
    background, there is a VERY light, but observable, magenta cast in some
    areas. The cast is more visible at the shadow end of my right column of
    the far left pair. The cast is on all three channels at the center, but
    more on r and b. What does this mean? Should everything on the chart be
    without any cast at all?

    My gamma is supposed to be at 2.2, and indeed that chart is the best
    when compared against charts of other gamma values. Perhaps this hint
    can be helpful.
     
    openmind, Jul 21, 2003
    #8
  9. Timo Autiokari

    openmind Guest

    Stephan is just like many other posters here. Language is the least of
    his problems. These posters attack those who differ from what they
    believe in and what they know (or think they know). They are firm
    believers that the earth is flat and that evolution is heresy, and want
    to put away all those who dare to think otherwise.
     
    openmind, Jul 21, 2003
    #9
  10. Timo Autiokari

    °¿° Guest


    Isn't it?
     
    °¿°, Jul 21, 2003
    #10
  11. Hi,

    Aha, that sure would help to understand the charts more easily, hmmm it
    need to be an illustration, not having the dithers, I'll see what can be
    done, until then any chart with gamma-space that is way different than what
    the system is set to is good for this purpose.
    Oh, they were stripes a long time ago, I've changed that now to say
    "pattern". There is similar kind of pattern (but in vertical) than what
    AdobeGamma shows, however the AdobeGamma "Brightness and Contrast" pattern
    is not correct, it outputs the very same RGB levels for the pattern no
    matter what "desired gamma" is selected, the fixed RGB values it outputs
    are good only for "desired value" of 2.5.
    Yes, for perfect calibration the chart should appear as pure gray all over.

    Now, the charts put the vision to an extremely sensitive state so a small
    cast (just discernible/detectable cast) is still an indication of good
    calibration. If you set the chart as the wallpaper you will most probably
    notice that the hue of the small cast changes as hours go by, this is due
    to the drift of the electronic components in the monitor.

    There is a color cast or tonal range (gray) difference in case:

    1) the tonal reproduction curve of the monitor (or the monitor path) does
    not follow the gamma law accurately (or if there is matrix or 3D look up
    table conversion such as a gamut or color-space conversion in the monitor
    path).

    2) if the blackpoint of the monitor is not accurately set.

    3) it is possible to get the cast also when using some existing profile as
    the starting point for AdobeGamma (profiles can be rather complex and
    AdobeGamma does not clean up everything in them). If the Description box in
    AdobeGamma says something else than "Adobe Monitor Settings" then
    AdobeGamma has used some profile as the starting point. The easiest way to
    start from the scratch is to zip compress all the profiles from the systems
    ICC profile directory (by *moving* to them the zip archive or just zipping
    first and then deleting the profiles) then when AdobeGamma is started the
    Description box will say "Adobe Monitor Settings" indicating that
    AdobeGamma has not read a profile in.

    The cast is either in the dark end or in the highlight depending on how you
    adjust the gamma sliders in the AdobeGamma.
    Blackpoint adjustment usually correct this.

    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 21, 2003
    #11
  12. Timo Autiokari

    Mike Russell Guest

    Fair enough. I've spend many an hour with Timo's gamma charts and recommend
    them to anyone who is interested in this issue.

    --

    Mike Russell
    http://www.curvemeister.com
    http://www.zocalo.net/~mgr
    http://geigy.2y.net
     
    Mike Russell, Jul 22, 2003
    #12
  13. Not sure how these are supposed to help with Adobe Gamma exactly. Maybe
    someone could explain it to me? I tried playing around and I think I've got
    my monitor pretty close to perfect, but it's curious that I have to enter a
    target gamma of 2.1 when making a profile in Adobe Gamma in order to achieve
    2.2 according to the charts on Timo's site. Not sure if this means anything
    at all or not...


    Hi,

    I've uploaded a set of unbearably accurate CRT gamma calibration charts:
    http://www.aim-dtp.net/aim/evaluation/gammaspace/index.htm
    Please have a look at them, I hope to hear if there is something to improve
    still.

    The above is in form of CRT gamma evaluation but you can right-click the
    chart (of the system gamma-space that you are calibrating to) and make the
    chart as the background image of your desktop, there it will help
    AdobeGamma calibration enormously.

    These chart are unbearably accurate since, with most consumer grade
    monitor, they make the small drift in the operation point of the monitor
    detectable. This drift can be rather rapid so that a change is detected
    within a hour or two or it can be very slow so that a change is detected
    only after some 8 to 24 hours of power on time.

    Timo Autiokari http://www.aim-dtp.net
     
    Katie Piecrust, Jul 22, 2003
    #13
  14. *Very* much. The gamma charts cover the full tonal range and they show the
    error in tonal difference and in hue difference where as the gamma patches
    in AdobeGamma have only one level.

    E.g. even if the blackpoint setup of your monitor has error you will still
    very easily end up with an incorrect match using AdobeGamma but the charts
    will show that there is error.
    Then your system gamma is 2.1.

    To get 2.2 use the 2.2 chart, adjust the blackpoint of the monitor
    accurately, set the "Desired gamma" in AdobeGamma to 2.2 and then use the
    sliders to calibrate.

    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 22, 2003
    #14
  15. Hello Katie,

    Aha. What I say is: When a particular gamma chart appears as gray all over
    (and the blackpoint checks are apper ok too) then your system (monitor) is
    effectively in that gamma space (no matter what value is in the Desired
    Gamma input box in AdobeGamma.

    What you have done is that you have some (not necessarily correct) gamma
    adjustments effective through the AdobeGamma sliders. Then you try to match
    a gamma chart using the Desired Gamma input box. This is not how the charts
    should be used.

    Do it this way:

    1. Make the 2.2 chart as the wallpaper of your desktop.
    2. Adjust the blackpoint correctly.
    3. Open AdobeGamma and set it to 2.2.
    4. Adjust the AdobeGamma sliders so that the chart appears gray all over.

    Then you are accurately in gamma 2.2. space. (it is much better to have
    the system in gamma 2.5 space since that is what the 99.999999% of the
    browsers on the Web are).

    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 22, 2003
    #15
  16. Ok, thanks for the information and your time. I think I've got it right now
    based on your instructions. Just one more question regarding Adobe Gamma. I
    couldn't get my monitor into a 2.2 gamma space when adjusting R, G, and B
    gammas individually, but I could do it if I viewed them as a single gamma.
    Is this ok, or is it better to adjust R G and B individually? Again, many
    thanks!


    Hello Katie,

    Aha. What I say is: When a particular gamma chart appears as gray all over
    (and the blackpoint checks are apper ok too) then your system (monitor) is
    effectively in that gamma space (no matter what value is in the Desired
    Gamma input box in AdobeGamma.

    What you have done is that you have some (not necessarily correct) gamma
    adjustments effective through the AdobeGamma sliders. Then you try to match
    a gamma chart using the Desired Gamma input box. This is not how the charts
    should be used.

    Do it this way:

    1. Make the 2.2 chart as the wallpaper of your desktop.
    2. Adjust the blackpoint correctly.
    3. Open AdobeGamma and set it to 2.2.
    4. Adjust the AdobeGamma sliders so that the chart appears gray all over.

    Then you are accurately in gamma 2.2. space. (it is much better to have
    the system in gamma 2.5 space since that is what the 99.999999% of the
    browsers on the Web are).

    Timo Autiokari http://www.aim-dtp.net
     
    Katie Piecrust, Jul 22, 2003
    #16
  17. Hi Katie,

    It is best when it can be done using the gray gamma slider only.

    Some (many) monitor have differences in the r, g, b gun characteristics so
    then one needs to use the individual sliders.

    All adjustment settings that the gray slider provides can be achieved with
    the r,g,b sliders also but it is somewhat more work that way.

    Actually the sliders really should be arranged better in AdobeGamma, one
    slider should be Luminosity and two should affect to the color/hue.

    BR,
    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 22, 2003
    #17
  18. Thanks for the warning, I think. Anything in particular you can point out
    for me that should be avoided in your opinion?



    Warning - Timo is a well known troll on usenet who seems to enjoy
    destroying other users' images. No, we don't know why he does this.

    Anything you "learned" on his site is probably wrong.

    Chris
     
    Katie Piecrust, Jul 23, 2003
    #18
  19. Hello Katie, Mr. Cox is not well, you can find
    what he points out here: http://tinyurl.com/hygv

    Timo Autiokari http://www.aim-dtp.net
     
    Timo Autiokari, Jul 24, 2003
    #19
  20. Timo Autiokari

    Mike Russell Guest

    Good point. I would add that one side of this frog-and-mouse battle relies
    on personal attacks, to the exclusion of technical discussion. The other
    does not.

    I'll leave it to you to figure out which is which.

    --

    Mike Russell
    http://www.curvemeister.com
    http://www.zocalo.net/~mgr
    http://geigy.2y.net
     
    Mike Russell, Jul 24, 2003
    #20
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