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CHROMAPURE GRAYSCALE & COLOR CALIBRATION FOR DUMMIES
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mfractal



Joined: 27 Mar 2016
Posts: 1
Location: Brazil


PostLink    Posted: Sun Mar 27, 2016 1:59 pm    Post subject: Reply with quote


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Quote:
It's also important to use the right test patterns for your display type. If you are calibrating a plasma or CRT display, always use window test patterns for grayscale, gamma, and color calibration. A window test pattern only fills the middle of the screen like this:

For display types that are not plasma or CRT, always use full field test patterns. A full field test pattern fills the entire screen like this:


Hi there. Planning to calibrate a Samsung JS8500 55" LED tv and not sure which patterns should i use. According to the instuctions full screen patterns should be used. The TV does however modify it's black levels in accordance to what is displayed on the screen. Ex. full black screen apprears extremely black, then say, subtitles appear - the whole black background gets brighter. Hope that makes sense Smile

So should i use full screen or field?
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kal
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Joined: 06 Mar 2006
Posts: 14313
Location: Ottawa, Canada

TV/Projector: JVC DLA-RS56


PostLink    Posted: Sun Mar 27, 2016 2:32 pm    Post subject: Reply with quote

Hi! Your display's not a plasma or CRT, so you would use full field test patterns.

Some TV do mess around with the black level based on content which can throw a wrench into the whole calibration process since you really don't know what the TV is doing or is going to do. You may want to try calibrating with those extra features turned on or off and see what kind of results you get.

Kal

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riesscar



Joined: 23 Jun 2016
Posts: 4



PostLink    Posted: Sat Aug 06, 2016 12:53 am    Post subject: Reply with quote

Greetings, and thank you for this clear and thorough guide! I own a retail iDisplay Pro for computer profiling, and I have recently been using it to calibrate HDTVs in the building where I work (there are 10 in total). I purchased Chromapure Standard Edition, along with licenses for my two colorimeters (I also own a Spyder 4). I also purchased the Chromapure calibration disc used in the guide. I have completed the tutorial on a few displays of different make, panel type and control options. I have a few questions that I hope someone might be able to assist with:

1) When I initialize my i1 Display Pro, there are only two modes in the drop-down menu (standard and front projector); however, in the tutorial it states that "NOTE: If you have a standard Display 3 meter (retail or OEM), then four operating modes will appear (Standard, Plasma, CRT, and Front Projection Lens)". Why might this be? The license lists the colorimeter as a Display 3 Pro, although I'm not sure why given that it is not one of the custom calibrated meter that s sold here. Could this be the problem?

2) When I initialize the meter and display a 100% white pattern, I get some strange values and variance, sometimes on the same display. For example, my Vizio LCD HDTV reported 60hz the first time I initialized the meter on it but has reported 120hz on all subsequent initializations. An example of what seems like a strange Hz rate would be my newer Vizio LED HDTV, which reported 480hz. Are these values normal? Is it detecting the screen refresh rate? If so, these readings must be inaccurate.

3) I am tempted to purchase your i1 Display Pro (retail) upgrade to a calibrated "Display 3 Pro", but I have reservations... At 175$ it costs almost as much as the meter. What sort of improvements might I hope to see. I will be calibrating TVs that range from CRT to LCD to Plasma to LED, and that stretch the gambit with regard to age and manufacturer. Additionally, what is the turnaround time on the calibration once I've sent the meter in?

4) On the white balance section of the tutorial, it states that it is best not to adjust the green value, but to reduce DeltaE using the red and blue controls. Why exactly is it ill-advised to adjust green? I find that without doing so I struggle to achieve balance.

5) In the color calibration section for TVs without a CMS, it states "Adjust the display's main color control on the display until you have minimized the red error for red, green, and blue.". What does this mean exactly? Do you mean to reduce red error for three different patterns? Or do you mean simply to reduce the red error for the sRGB color space? I hope this question makes sense.

6) On two of my displays I have access to a CMS. I have been able to use both to some effect, but I don't understand how the three HSL values interact. How can I increase the saturation of a color without increasing its luminance? I have no idea how to fine-tune hue. Do you have any tips on how to adjust the HSL values in a CMS? Is it best to start with one or another?

7) Lastly, when a display lacks gamma controls or options and I end up with a Gamma value which falls short of 2.22 (say 2.15 for instance), do you recommend reducing contrast or brightness in order to raise the gamma, or is this a matter of preference which is unique to each screen/person.

Thanks so much for any help/advice you might provide, and thank you again for the great tutorial!
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kal
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Joined: 06 Mar 2006
Posts: 14313
Location: Ottawa, Canada

TV/Projector: JVC DLA-RS56


PostLink    Posted: Sat Aug 06, 2016 3:04 pm    Post subject: Reply with quote

riesscar wrote:
Greetings, and thank you for this clear and thorough guide!

Glad you like it! I've asked the author of ChromaPure (Tom) to chime in here and answer some of your questions as they're best positioned to answer some of them. I can help with this one however:

Quote:
3) I am tempted to purchase your i1 Display Pro (retail) upgrade to a calibrated "Display 3 Pro", but I have reservations... At 175$ it costs almost as much as the meter. What sort of improvements might I hope to see. I will be calibrating TVs that range from CRT to LCD to Plasma to LED, and that stretch the gambit with regard to age and manufacturer.

That's a difficult question to answer as it depends how "off" your meter is to begin with. Until we get in the lab and measure against reference, we don't know how much improvement you will see. The older the meter, the more improvement you're likely to see. A certificate of calibration is included with all calibrations so that you see the differences yourself. Here's an example:


More info: http://www.curtpalme.com/forum/viewtopic.php?t=36772

Quote:
Additionally, what is the turnaround time on the calibration once I've sent the meter in?

Tom can chime in on this too but I believe the actual lab time is fairly fast (a day or so). Most of the waiting is for transit there and back.

Cheers,

Kal

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TomHuffman



Joined: 01 Jun 2010
Posts: 58
Location: Springfield, MO


PostLink    Posted: Sat Aug 06, 2016 8:08 pm    Post subject: Reply with quote

riesscar wrote:
1) When I initialize my i1 Display Pro, there are only two modes in the drop-down menu (standard and front projector); however, in the tutorial it states that "NOTE: If you have a standard Display 3 meter (retail or OEM), then four operating modes will appear (Standard, Plasma, CRT, and Front Projection Lens)". Why might this be? The license lists the colorimeter as a Display 3 Pro, although I'm not sure why given that it is not one of the custom calibrated meter that s sold here. Could this be the problem?
Yes. You will have additional modes only if we calibrate the meter.

2) When I initialize the meter and display a 100% white pattern, I get some strange values and variance, sometimes on the same display. For example, my Vizio LCD HDTV reported 60hz the first time I initialized the meter on it but has reported 120hz on all subsequent initializations. An example of what seems like a strange Hz rate would be my newer Vizio LED HDTV, which reported 480hz. Are these values normal? Is it detecting the screen refresh rate? If so, these readings must be inaccurate.
It doesn't matter. The meter will always report some multiple of 60 for NTSC displays.

3) I am tempted to purchase your i1 Display Pro (retail) upgrade to a calibrated "Display 3 Pro", but I have reservations... At 175$ it costs almost as much as the meter. What sort of improvements might I hope to see. I will be calibrating TVs that range from CRT to LCD to Plasma to LED, and that stretch the gambit with regard to age and manufacturer. Additionally, what is the turnaround time on the calibration once I've sent the meter in?
Turnaround time is just a couple of days. The improvement can be significant with LED displays, less so with front projectors and LCDs. Plasmas are somewhere in between.

4) On the white balance section of the tutorial, it states that it is best not to adjust the green value, but to reduce DeltaE using the red and blue controls. Why exactly is it ill-advised to adjust green? I find that without doing so I struggle to achieve balance.
Because green substantially affects gamma and overall light output.

5) In the color calibration section for TVs without a CMS, it states "Adjust the display's main color control on the display until you have minimized the red error for red, green, and blue.". What does this mean exactly? Do you mean to reduce red error for three different patterns? Or do you mean simply to reduce the red error for the sRGB color space? I hope this question makes sense.
The software reports errors for red, green, and blue. Choose the Color setting that provides the lowest error in red.

6) On two of my displays I have access to a CMS. I have been able to use both to some effect, but I don't understand how the three HSL values interact. How can I increase the saturation of a color without increasing its luminance? I have no idea how to fine-tune hue. Do you have any tips on how to adjust the HSL values in a CMS? Is it best to start with one or another?
The interaction between saturation and luminance depends on how the CMS is designed. Regarding hue, select the setting that results in the lowest dE.

7) Lastly, when a display lacks gamma controls or options and I end up with a Gamma value which falls short of 2.22 (say 2.15 for instance), do you recommend reducing contrast or brightness in order to raise the gamma, or is this a matter of preference which is unique to each screen/person.
No, in such a case there's really nothing you can do about this, unless you have 10-point RGB white balance controls. If you do, then you can use the green cointrol to adjust gamma, making sure to also use red and blue to maintain good white balance.

Thanks so much for any help/advice you might provide, and thank you again for the great tutorial!

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riesscar



Joined: 23 Jun 2016
Posts: 4



PostLink    Posted: Sun Aug 07, 2016 4:33 am    Post subject: Reply with quote

Thanks so much for the responses!
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riesscar



Joined: 23 Jun 2016
Posts: 4



PostLink    Posted: Mon Aug 08, 2016 11:59 pm    Post subject: Reply with quote

Greetings again! I wonder if I might submit a few more inquiries:

1) When calibrating colors, the tutorial says to display a color pattern (plume) at 100%. The issue that I'm having is that if I set my luminosity (Y) to 120cd/m, my dE is always way off due to the my color luminosity. I have read on other tutorials that color should be calibrated using 75% signal test patterns, but when I think about it I'll have failed to calibrate my colors according to the white point... right?

2) On a related note, I have found that if I am calibrating a display that has a CMS (an HSL system), and I reduce the luminosity of a color to reduce dE, I end up with far worse color inaccuracies at lower luminosities (75,50,25). Conversely, if I accept my luminance errors and resulting high dE, I end up with more accurate colors at 75%. I don't understand how I can calibrate a color, if it doesn't scale across saturation and luminance intensities. (I could be way off here... I hope my question is comprehensible :/)

3) I've discovered inconsistencies between two other calibration programs and ChromaPure when taking readings. In addition to ChromaPure Standard Edition, I have Calman Control and Spyder HD. I wanted to see how SpyderHD's simple workflow does as a preliminary calibration, which I did using Calman Control's Andvanced Workflow. I fine-tuned the rudimentary calibrations done by SpyderHD, calibrating the white point and greyscale, setting the sharpness, and further calibrating colors using the display's CMS -- this is in addition to the main color and tint adjustments already done. I was able to get pretty good results... the readings I did just to compare with the Spyder4 values were either the same or within the margin of error. However, when I looked at the readings reported between Calman and ChromaPure, I was concerned to see very different numbers. For example, my dE error on the white point and along the grayscale rose substantially, my Gamma curve was no longer linear and dropped off at the 80-90% mark, and my reported color error went from less than 5 dE max to numbers as high as 35 (again with luminosity errors being most severe). Moreover, I have found strange variance between readings in different modules within ChromaPure! For example, if I open the color management module and calibrate successfully using a 100% red pattern, I get a different reading from the same source within the post-calibration color gamut module. A final worry is that when I display a 100% white internal pattern from a TV, it is read as having a much higher Y value and different RGB levels than the 100% White test patterns on the ChromaPure Calibration disc. Can anyone think of a reason that my software would be receiving different readings from multiple others (Spyder HD, Calman Control, and iProfiler) while using the same colorimeter (on two of them, since I used the Spyder4 on its software)? I checked the settings on both programs, and aside from a few options available in one and not another (measurement smoothing etc) they are the same.

Thanks for any guidance,

Carson
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TomHuffman



Joined: 01 Jun 2010
Posts: 58
Location: Springfield, MO


PostLink    Posted: Wed Aug 10, 2016 12:25 am    Post subject: Reply with quote

riesscar wrote:
Greetings again! I wonder if I might submit a few more inquiries:

1) When calibrating colors, the tutorial says to display a color pattern (plume) at 100%. The issue that I'm having is that if I set my luminosity (Y) to 120cd/m, my dE is always way off due to the my color luminosity. I have read on other tutorials that color should be calibrated using 75% signal test patterns, but when I think about it I'll have failed to calibrate my colors according to the white point... right?
If you are using v3, you should always use a 100% white reference even if you selected 75% intensity on the main page and used 75% intensity color patterns. If you select 100% intensity, then use 100% white and 100% color.
2) On a related note, I have found that if I am calibrating a display that has a CMS (an HSL system), and I reduce the luminosity of a color to reduce dE, I end up with far worse color inaccuracies at lower luminosities (75,50,25). Conversely, if I accept my luminance errors and resulting high dE, I end up with more accurate colors at 75%. I don't understand how I can calibrate a color, if it doesn't scale across saturation and luminance intensities. (I could be way off here... I hope my question is comprehensible :/)

Try calibrating at 75% intensity instead of 100%. That is more likely to provide reasonable p-erformance throughout the color range.

3) I've discovered inconsistencies between two other calibration programs and ChromaPure when taking readings. In addition to ChromaPure Standard Edition, I have Calman Control and Spyder HD. I wanted to see how SpyderHD's simple workflow does as a preliminary calibration, which I did using Calman Control's Andvanced Workflow. I fine-tuned the rudimentary calibrations done by SpyderHD, calibrating the white point and greyscale, setting the sharpness, and further calibrating colors using the display's CMS -- this is in addition to the main color and tint adjustments already done. I was able to get pretty good results... the readings I did just to compare with the Spyder4 values were either the same or within the margin of error. However, when I looked at the readings reported between Calman and ChromaPure, I was concerned to see very different numbers. For example, my dE error on the white point and along the grayscale rose substantially, my Gamma curve was no longer linear and dropped off at the 80-90% mark, and my reported color error went from less than 5 dE max to numbers as high as 35 (again with luminosity errors being most severe). Moreover, I have found strange variance between readings in different modules within ChromaPure! For example, if I open the color management module and calibrate successfully using a 100% red pattern, I get a different reading from the same source within the post-calibration color gamut module. A final worry is that when I display a 100% white internal pattern from a TV, it is read as having a much higher Y value and different RGB levels than the 100% White test patterns on the ChromaPure Calibration disc. Can anyone think of a reason that my software would be receiving different readings from multiple others (Spyder HD, Calman Control, and iProfiler) while using the same colorimeter (on two of them, since I used the Spyder4 on its software)? I checked the settings on both programs, and aside from a few options available in one and not another (measurement smoothing etc) they are the same.

I cannot answer any of this without some actual data. Please send to ChromaPure Support instead of here. I need a calibration report.

Thanks for any guidance,

Carson

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riesscar



Joined: 23 Jun 2016
Posts: 4



PostLink    Posted: Wed Aug 10, 2016 1:01 am    Post subject: Reply with quote

Thanks for the response. I'll go ahead and refer my question about readings to ChromaPure.

Carson
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kal
Forum Administrator


Joined: 06 Mar 2006
Posts: 14313
Location: Ottawa, Canada

TV/Projector: JVC DLA-RS56


PostLink    Posted: Thu Feb 09, 2017 3:24 am    Post subject: Reply with quote

The guide has been updated!:

- Added ChromaPure 3.1 support (all new screenshots and instructions)
- Added Rec. 2020/UHD/HDR support

Kal

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