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Author Topic: iMac calibration/profiling  (Read 14841 times)
jjlphoto
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« on: February 20, 2009, 05:28:59 PM »
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A friend of mine just bought a brand new Apple iMac. I've the GMB i1Pro device, so I offered to do a cal/profile on his display. (According to the GMB license, I can legally install the i1 Match3 software on another person's machine.)

In the i1 Match 3 v3.6.2 wizard, I set the desired target values to 120 cd/m2, 6500K, and 2.2. I slid the brightness slider in the iMacs Display Prefs to minimum, but the lowest the iMac will go is 230 cd/m2. Is he simply stuck with a machine that is not designed to be properly cal/profiled?
« Last Edit: February 20, 2009, 05:40:28 PM by jjlphoto » Logged

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Czornyj
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« Reply #1 on: February 20, 2009, 05:48:39 PM »
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Quote from: jjlphoto
A friend of mine just bought a brand new Apple iMac. I've the GMB i1Pro device, so I offered to do a cal/profile on his display. (According to the GMB license, I can legally install the i1 Match3 software on another person's machine.)

In the i1 Match 3 v3.6.2 wizard, I set the desired target values to 120 cd/m2, 6500K, and 2.2. I slid the brightness slider in the iMacs Display Prefs to minimum, but the lowest the iMac will go is 230 cd/m2. Is he simply stuck with a machine that is not designed to be properly cal/profiled?

It's a common problem - not only with iMac.
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Marcin Kałuża
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« Reply #2 on: February 20, 2009, 06:31:36 PM »
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Is that 230 the value the software returned AFTER calibration and profiling or before? If before, after you finished the calibration and the profiling what L value did the software return?
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Mark D Segal (formerly MarkDS)
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John MacLean
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« Reply #3 on: February 20, 2009, 09:58:54 PM »
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Quote from: jjlphoto
A friend of mine just bought a brand new Apple iMac. I've the GMB i1Pro device, so I offered to do a cal/profile on his display. (According to the GMB license, I can legally install the i1 Match3 software on another person's machine.)

In the i1 Match 3 v3.6.2 wizard, I set the desired target values to 120 cd/m2, 6500K, and 2.2. I slid the brightness slider in the iMacs Display Prefs to minimum, but the lowest the iMac will go is 230 cd/m2. Is he simply stuck with a machine that is not designed to be properly cal/profiled?

I've spoken to the xrite sales rep Marty Glickman about this before and he said the luminance will get adjusted to the proper level by the Match software. Not the best case scenario but it works.

However THIS article doesn't give too much credence to the display itself.

Working with the new Intel iMac
"Why an iMac? Well, I shoot a lot on location or in hire studios, so a portable computer is essential and I find that iMacs offer a high-powered computer with a large built-in. These are easy to transport and suit the way I work. Now regarding the new 24″ iMac I can confirm that there is a problem with the display on my screen. The left half of the display is brighter and it is impossible to set the brightness any lower than 215 cd m2. Worse still, I have not been able to generate a decent monitor profile using the Eye-One pro and ColorMatch software. It is a significant enough problem that I have found it impractical to use for judging how photographs look in Lightroom or Photoshop. The highlight tones are so blown out that I can’t tell the difference between white and off-white, which results in skin tones looking washed out and lacking in contrast. This is definitely the worse quality monitor I have ever had to work with. My solution, as you can see from the intro picture, has been to rig up an Apple 23″ LCD display as a second monitor and use this to view the photos."
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jjlphoto
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« Reply #4 on: February 21, 2009, 12:26:02 PM »
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Quote from: MarkDS
Is that 230 the value the software returned AFTER calibration and profiling or before? If before, after you finished the calibration and the profiling what L value did the software return?
As stated in my OP:
in the i1 Match 3 v3.6.2 wizard, I set the desired target values to 120 cd/m2.
After the cal/profile was complete, the final reading is always +-230cd/m2. I set it side by side with my Eizo, both displaying my favorite Andrew Rodney test image, and his looked substantially lighter.


Quote from: John MacLean
I've spoken to the xrite sales rep Marty Glickman about this before and he said the luminance will get adjusted to the proper level by the Match software. Not the best case scenario but it works.
Total BS. See above.


Quote
The left half of the display is brighter and it is impossible to set the brightness any lower than 215 cd m2. Worse still, I have not been able to generate a decent monitor profile using the Eye-One pro and ColorMatch software.
His has the same uneven appearance, even after substantial warm-up. After the cal/profile was made (I did it three times), I did the gray scale test, and it rendered a very choppy looking gradient, and there was a lot of magenta/green rainbowing.

He's got another friend with a Monoco Optix and the corresponding software. I wonder if that package will be able to drive his luminance level down?

Thanks for all the feedback guys. Glad its not mine.
« Last Edit: February 21, 2009, 12:36:50 PM by jjlphoto » Logged

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jackbingham
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« Reply #5 on: February 21, 2009, 12:55:54 PM »
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Ok, lets go through this again.
The Imac out of the factory will only go so dim. Why they built it this way I have no clue. That being said you can set the brightness on these manually to 10% or so and then use calibration software to adjust the brightness in the video card. Not ideal but it does work and can be a reasonable solution. The unevenness of these particular displays is a good reason for a return. Calibration can't help that problem.
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Jack Bingham
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jjlphoto
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« Reply #6 on: February 21, 2009, 02:03:28 PM »
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Quote from: jackbingham
....The Imac out of the factory will only go so dim. Why they built it this way I have no clue. That being said you can set the brightness on these manually to 10% or so and then use calibration software to adjust the brightness in the video card...

How do you do that Jack? Before running the cal/profile, I went to the Display Prefs and slid the brightness slider all the way to the left, which is minimum. Is there something I am missing?
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jackbingham
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« Reply #7 on: February 21, 2009, 02:32:47 PM »
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John, I can't speak for any other piece of software, but with Coloreyes you select the LCD Brightness only monitor plugin, set your target white point luminance to the value you want and profile. The adjustment will be made in the video card. I would assume you could do the same thing with any other calibration tool.
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Jack Bingham
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jjlphoto
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« Reply #8 on: February 21, 2009, 02:44:25 PM »
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Quote from: jackbingham
John, I can't speak for any other piece of software, but with Coloreyes you select the LCD Brightness only monitor plugin, set your target white point luminance to the value you want and profile. The adjustment will be made in the video card. I would assume you could do the same thing with any other calibration tool.

Same with GMB i1 Match3. In the start-up window in the wizard, the user can set their desired target points. I selected a lum of 120cd/m2. But that bloody iMac is so bright right out of the box, the GMB software can only drop the displays lum so much, even with the display manually set to minimum in the OSX Display Prefs.
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jackbingham
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« Reply #9 on: February 21, 2009, 03:09:28 PM »
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Perhaps you should download the Coloreyes demo and give that a spin.
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Jack Bingham
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« Reply #10 on: February 21, 2009, 03:38:16 PM »
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I've read about an app called "Shades" which allows you to lower the brightness of an iMac.  For every person who recommends it, there's somebody else who slams it, but it's worth trying.
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Damien
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« Reply #11 on: February 21, 2009, 03:49:53 PM »
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Actually it is not worth trying. Here's why. You build your profile based on the output of the video card and then you make a brightness adjustment with shades. Now your profile is worthless unless you can make the leap that changing the brightness out put of the card won't change anything else. All shades does is adjust the output of the video card. And it will only work after profiling. With a shades adjustment in place, building a new calibration and profile will reset it. So now you need to go back and set it again and wreck your profile.
It's a non-starter if profiling is important.
« Last Edit: February 21, 2009, 03:50:45 PM by jackbingham » Logged

Jack Bingham
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« Reply #12 on: February 22, 2009, 03:59:07 AM »
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Hmmm ...

Well, in that case, John's friend should simply work in a very bright room
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Damien
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« Reply #13 on: February 24, 2009, 07:37:41 AM »
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Quote from: jjlphoto
As stated in my OP:
in the i1 Match 3 v3.6.2 wizard, I set the desired target values to 120 cd/m2.
After the cal/profile was complete, the final reading is always +-230cd/m2. I set it side by side with my Eizo, both displaying my favorite Andrew Rodney test image, and his looked substantially lighter.

OK, thanks for clarifying - it wasn't obvious to me at what point in the process you got that very bright reading. The reason I asked is exactly what Jack Bingham mentioned - one expects (based on CED experience anyhow) that the calibration/profiling software should adjust the video card to deliver approximately the cd/mm2 you asked for as an input to the calibration. One wonders in this case whether the problem of reducing iMac's brightness is largely due to the video card or to the display or both. It just crossed my mind - and without knowing anything about the build of this computer - that perhaps the card can be changed if that's the source of the problem?
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
jackbingham
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« Reply #14 on: February 25, 2009, 06:10:11 PM »
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Mark this is really very simple. The imac out of the box is too bright. Drag the brightness slider all the way to dim and you could still have 200+. The only solution is to drag the slider down to 10% or so and then have your calibration software do the rest in the video card. Simple,  non-elegant solution to a less than ideal manufacturing practice.
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Jack Bingham
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« Reply #15 on: February 25, 2009, 07:12:54 PM »
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Jack, yes - sounds completely sensible as you put it. But I've heard - forget where, and don't know whether this is true - that making very large calibration adjustments in video cards can cause them to have other problems rendering accurate images, hence it's better done in the display itself (clearly very constrained in this case). Anything to this general point?
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Mark D Segal (formerly MarkDS)
Author: "Scanning Workflows with SilverFast 8....." http://www.luminous-landscape.com/reviews/film/scanning_workflows_with_silverfast_8.shtml
jackbingham
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« Reply #16 on: February 26, 2009, 08:00:52 AM »
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As a general rule making calibration adjustments to monitor internal high bit luts will always be better than making color and brightness adjustments to video cards. However in the absence of that ability you have only two choices. Settle for a less than ideal color match to print or in some cases suffer with some banding in the shadows. Most monitor calibration tools these days do a very good job of smoothing out the banding. I have several imacs myself that I run at d50 or so, measured from my viewing booths, the banding is minimal and the color match is right on. In my mind the color match is a much more critical factor than some banding.
The imac is a compromise from the start so you have to pick your demon.
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Jack Bingham
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« Reply #17 on: February 26, 2009, 08:14:17 AM »
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Quote from: Damo77
Hmmm ...
Well, in that case, John's friend should simply work in a very bright room

Just raise the luminance of the viewing booth by the display to result in a visual match. Keep the ambient light low if possible (it can't be too low).
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Andrew Rodney
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« Reply #18 on: February 26, 2009, 05:01:57 PM »
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Geez Andrew, how is that even vaguely relevant?  Not only has John's friend bought a fairly run-of-the-mill consumer computer, he hasn't even sprung for his own calibrator, so I think the chance of him owning a viewing booth is pretty remote, don't you?
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Damien
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« Reply #19 on: February 26, 2009, 05:15:36 PM »
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Quote from: Damo77
Geez Andrew, how is that even vaguely relevant?  Not only has John's friend bought a fairly run-of-the-mill consumer computer, he hasn't even sprung for his own calibrator, so I think the chance of him owning a viewing booth is pretty remote, don't you?

He's got to calibrate the damn thing. But he's got to take viewing conditions into mind before he can set calibration. You can't match a viewing booth to a display without having some idea you will drive the booth to set luminance.
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Andrew Rodney
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