yCMS - Color Management System

[yesgrey]

I got an error that I should give the numbers in increasing order. My IRE list was: 0, 1, 2, 3, 4, 10, 20, 30, 50, 70, 100. So, the real problem is that I should keep equal steps between values or I can not use too little steps.
There isn't such a limitation. The measures values should also be in increasing order, have you checked that? but that would not help you. I've already said that it's a bug. It's preferable to not use the Grayscale_Measurements command with the current version of yCMS. I'm working on it...

[iSeries]

Hi,

I'd like to have a go at creating a 3D LUT but to be honest after reading the 'manual' I am no more clued up than before. Is there a 'dummies' guide anywhere?

I have not calibrated my TV but someone on a well known AV forum posted profesional IRE calibration results. I've applied these through the 'Picture' menu of my TV (and improved colour 100%) but how can I apply these numbers to a 3D LUT?

Sorry for the newbie-ness :)

[janos666]

There isn't such a limitation. The measures values should also be in increasing order, have you checked that? but that would not help you. I've already said that it's a bug. It's preferable to not use the Grayscale_Measurements command with the current version of yCMS. I'm working on it...

No, there were 11 numbers in increasing order, like I wrote and I got that message.
May be there were some fluctuation in the RGB luminance values and (for example) R-2% was less than R-1%. (I checked the "Average many readings" but my display do not has internal LUT for gamma and software LUT won't give me perfect result through 8 bit link. - After you released this new yCMS and I started to examine dark gradiations I feel that I need a new display. :p)
I just recalibrated my display and noticed this "Near Black Scale" tab in HCFR, so I thoght it won't harm if I give it a try. It won't be a bad idea to increase the max IRE number to 14 either. (To add this near black scale too - as an experiment. It looks like PVA displays without internal LUT has strange gradiation near to black. I didn't noticed it with my S-PVA earlier but it is clearly noticeable with c-PVA panels and exists here too.)


But can you upload yCMS 1.0 or the latest cr3dlut version for me? I can't remember if I saw something like this in the past (only with simple gamut correction): 3DLUT OFF (http://img12.tar.hu/janos666/img/76795039.png) - ON (http://img12.tar.hu/janos666/img/76795040.png)
I didn't keep any old versions and I would watch movies until your next yCMS release. Thanks. :)


Hi,

I'd like to have a go at creating a 3D LUT but to be honest after reading the 'manual' I am no more clued up than before. Is there a 'dummies' guide anywhere?

I have not calibrated my TV but someone on a well known AV forum posted profesional IRE calibration results. I've applied these through the 'Picture' menu of my TV (and improved colour 100%) but how can I apply these numbers to a 3D LUT?

Sorry for the newbie-ness :)

First:
Using measures from others can result in better or worse state as well. If every display would be identical then they wouldn't be calibrated at home (and recalibratead about monthly period), they could be easily calibrated in the factory. (Some manufacturers do this for their displays one by one and you only have to fine tune it at home, if you want...)
But native primary colors should be close (with identical brightness and contrast settings), so you can use those coordinates to do a gamut correction (if necessary).
Second:
If your display has configurable internal CMS then you are very lucky and you do not need software CMS. I do not know the capabilities of your hardware and what settings did you applied exactly...
Third:
Here is a template. You should change the last 4x2 values (four substantional value would be enougt - I just copy-pasted them...) . These are the x;y CIE coordinates of Red, Green, Blue, White colors (in this order).
As yesgrey wrote it earlier too, you should not try to use IREs for gamma correction with current software versions.
Filename: HD - PC.txt

# Source video format
Input_Format HD YCbCr 8

#3DLUT output format
Output_Format HD RGB_PC 16

# Gamut correction - measured native x;y coordinates
Gamut_Measurements 0.655471 0.330898 0.232747 0.689508 0.140942 0.090273 0.311221 0.327337

[iSeries]

Thanks janos666 - yes I'm aware using someone elses calibration results will not be 100% perfect, but trust me, its miles better than it was (even Cinema mode was too blue - my TV is a LG 47LH5000).

I have a Spyder3 - can I use this to get the necessary measurements? If so, what software should I use?

[janos666]

Thanks janos666 - yes I'm aware using someone elses calibration results will not be 100% perfect, but trust me, its miles better than it was (even Cinema mode was too blue - my TV is a LG 47LH5000).

I have a Spyder3 - can I use this to get the necessary measurements? If so, what software should I use?

Of course. It will be very easy if the display is connected to a PC through a digital cable and it won't be too hard if it is not.
Install this free software: Color HCFR (http://www.homecinema-fr.com/colorimetre/index_en.php).
Put some DLL files to it's folder from your bundled calibration software's folder if you asked to do it. (There will be a detailed notice later. Then start again from here...)
Start a new "View images" document, select your instrument from the list.
Set the output range of the image generator as your display requires it. (0-255 for PC monitors and sometimes for TVs which are connected to PC and normally 16-235 for TVs with any input source. You can figure it out with a quick test. Watch a black image. If it is black with 16-235 range then output setting is right.)
Do a complete measure set by clicking on the icon with many colored rings. Wait until it finished and save the document for later.
May be you have to cancel the first attempt and start it again if it would hang on showing a black image. I usually have to double click on the black image, wait, hit ESC, hit OK and start it a second time to do a correct measure set...

If you can't connect the display to a PC then you need the AVS HD 709 test patterns (http://www.avsforum.com/avs-vb/showthread.php?t=948496) and play it back on your player to manually measure the primaries (or grayscale, ect.) in free measure mode.
But yes, I could figure it out that you have a PC because yCMS can be used with PC softwares (like madVR video renderer) only.

You can select the Primaries and Secondaries tab, set the xyY format and copy-past the R,G,B,W columns to a text file, clear the Y value and sort it.
Or you can choose the Grayscale tab and the RGB value format to get color luminance values for IREs.

Another thing: If you watch movies from your PC than you can use the calibration software to correct your gamma curve. The problem is that I do not know any free/bundle software which can work with a real Rec709 tonal response curve. But it won't be a problem if you target a gamma function like x^2.2. (I am not sure yet if in the real life, most HDTVs really use the Rec709 inverse transfer function or they have a simple gamma curve like x^2.2)

[Mark_A_W]

Do a measurement set with HCFR (primary colors and white will be enough for now but grayscale could be useful later, so choose the icon with the most rings...) and use copy-paste (CTRL+C and CTRL+V keys on your keyboard) the xyY values to a text file, delete the Y values and sort the xy values (in R G B W order) to a row and copy-paste it after the Gamut_Measurements command in your yCMS settings file.
You can do the same with grayscale RGB values but I do not think it is useful with current softwares.

Of course. It will be very easy if the display is connected to a PC through a digital cable and it won't be too hard if it is not.
Install this free software: Color HCFR (http://www.homecinema-fr.com/colorimetre/index_en.php).
Put some DLL files to it's folder from your bundled calibration software's folder if you asked to do it. (There will be a detailed notice later. Then start again from here...)
Start a new "View images" document, select your instrument from the list.
Set the output range of the image generator as your display requires it. (0-255 for PC monitors and sometimes for TVs which are connected to PC and normally 16-235 for TVs with any input source. You can figure it out with a quick test. Watch a black image. If it is black with 16-235 range then output setting is right.)
Do a complete measure set by clicking on the icon with many colored rings. Wait until it finished and save the document for later.
May be you have to cancel the first attempt and start it again if it would hang on showing a black image. I usually have to double click on the black image, wait, hit ESC, hit OK and start it a second time to do a correct measure set...

If you can't connect the display to a PC then you need the AVS HD 709 test patterns (http://www.avsforum.com/avs-vb/showthread.php?t=948496) and play it back on your player to manually measure the primaries (or grayscale, ect.) in free measure mode.
But yes, I could figure it out that you have a PC because yCMS can be used with PC softwares (like madVR video renderer) only.

You can select the Primaries and Secondaries tab, set the xyY format and copy-past the R,G,B,W columns to a text file, clear the Y value and sort it.
Or you can choose the Grayscale tab and the RGB value format to get color luminance values for IREs.

Another thing: If you watch movies from your PC than you can use the calibration software to correct your gamma curve. The problem is that I do not know any free/bundle software which can work with a real Rec709 tonal response curve. But it won't be a problem if you target a gamma function like x^2.2. (I am not sure yet if in the real life, most HDTVs really use the Rec709 inverse transfer function or they have a simple gamma curve like x^2.2)



Janos, it seems to me from the first post that you are talking about doing Gamut cropping - as you are measuring primaries only, not greyscale.


But from the second post you kinda are talking about a custom gamma curve, which would need a greyscale measurement.


And we would need a target curve input somewhere.

What if I don't want the end result to be 2.2? What if I want, say, 2.5? Or a non-standard result?


It still seems to me that something is missing between the raw measurements and yCMS.


But we are getting somewhere :)

[cyberbeing]

But there is a huge bug with the out of gamut colors (I think) in this version. Take a look at the blue area on the upper left corner: off (http://img12.tar.hu/janos666/img/76364851.png) - on (http://img12.tar.hu/janos666/img/76364853.png)

I've run into this problem as well with a couple different videos. The yCMS created LUT creates black blocks within portions of certain video sequences (repeatable). Until some of these bugs get fixed, I've rolled back to using cr3dlut which at least was 'stable' (yet no longer available on your website). Hint: It may be nice if you continued to make cr3dlut available until you can consider yCMS as being 'stable', without any significant bugs.

[iSeries]

@ janos666 - this isn't going to be as simple as I'd hoped! I've copied spyder3.dll to the install directory as it asked but when I try to start the measurements the software is saying 'Spyder3.dll returned an error during initialisation', and then 'Error during sensor initialisation'. Any ideas?

[yesgrey]

What if I don't want the end result to be 2.2? What if I want, say, 2.5? Or a non-standard result?
That's the next thing I will take care after solving the current issue with Grayscale_Measurements. It's a subject that will need some discussion, so we'll get back to it after I fix the Grayscale_Measurements... Don't forget yCMS is still a new-born... ;)

I've run into this problem as well with a couple different videos. The yCMS created LUT creates black blocks within portions of certain video sequences (repeatable).
I thought the problem only affected the Grayscale_Measurements command, but I've also fixed a bug that might affect the image even when it's not used.
Can you upload a small video sample? If that fixed bug solves the problem I will soon release a new yCMS version.

[cyberbeing]

Here you go (blocking appears in the blue haze around the 4 second mark):
http://www.mediafire.com/?mdmvmnyzqom

The other time it occurred it was in a blue area as well, but I forgot what video showed it. The image janos666 posted also had blocking in a blue area, so maybe it only effects blue? Or possibly any significantly out of gamut colors for any primary?

# Set input format
Input_Format HD YCbCr 8

# Set output format
Output_Format HD RGB_PC 16

# Display Gamut Measurements
Gamut_Measurements 0.626 0.343 0.294 0.607 0.149 0.078 0.3127 0.3290

[janos666]

@cyberbeing
I can notice it with blue colors only but this is the only primary color where the native point does not reach the Rec709 reference point, and it is out of the reference rectangle. I posted my gamut measures in #53
Here is an other blue sample: NLC logo (http://www.tar.hu/janos666/Sample.blueblank.mkv) (<- Right click, save as).
I can see some strange things with red colors as well but I can reproduce them with one movie only (Cargo), so it can be some encoding/decoding bug. There are some strange things with red scenes but they looks strange without 3DLUT processing as well. So I think that gamut conversion makes it more strange only. (Closed area, intense red light, red faces...)

@Mark_A_W
Yes. As yesgrey wrote it, we should do gamut correction only with current versions. But I suggested for him to measure the grascale as well if he already placed the instrument on his display because it can be useful in the (near?) future.
The other thing what I suggested that he can use PC softwares for gamma correction through VGA LUT. Some calibration softwares will let you define custom x^y gamma curves or sRGB curve, and a few (expensive) one will let you choose Rec709 or even allow you to define a custom math definition for any complex curves. The result won't be too close to perfect if you do not have 10+ bit output from your VGA but it will be close enough when you want a curve which is close to the native characteristics.

But this is a very complicated story. I was not able to figure it out yet that I should use sRGB or x^2.2 curve for a general purpose home PC. There are some arguments on both sides but I think that there is no one correct answer here. It is more like a recommendation. I used sRGB curve in the last few months but I calibrated my display with x^2.2 same days ago.
And the only software which can do Re709 calibration (as I know) is CalMan. That is more expensive than my EyeOne itself. And I do not want to manually load the VGA LUTs every time I watch movies.

So, my display will be calibrated to sRGB or x^2.2 (with VGA LUT) and I will convert the Rec709 sources with yCMS to match with this characteristic.


@iSeries
Sorry. I feel this is off-topic here, and I am not so familiar with Spyders. May be they can help: Color HCFR Calibration Discussion @ AVS Forum (http://www.avsforum.com/avs-vb/showthread.php?t=786966). But it will be some incompatibility with your DLL or device driver version.

[yesgrey]

yCMS v1.2 released

http://yesgrey.com/ycms.html

- Fixed corruption of blue and red at very low levels.

This is a new version only for fixing the corruption of blue and red at very low levels, noted by several users.

It's still recommended to not use the Grayscale_Measurements command until I fix what's wrong with it.

[yesgrey]

so maybe it only effects blue?
I can see some strange things with with red colors as well
You were both correct. The bug affected both blue and red at very low levels.

Let me know how it works with v1.2.

Thanks for reporting the problem.

[cyberbeing]

yCMS 1.2 fixes the sample I posted.

Is there a reason why you removed the Out_Of_Gamut_Clipping option which was in cr3dlut? Previously I always used the Simple method (if >1.0 -> 1.0; if <0.0 -> 0.0), which I assume is similar to Relative Colorimetric. Same goes for the Chromatic_Adaptation parameter.

Another thing which would be nice is if yCMS automatically outputted LUTs with the .3dlut extension, unless a different extension is specified.

[janos666]

The bug affected both blue and red at very low levels.
Let me know how it works with v1.2.

Yes, it is much better now. But still not perfect. Play my sample file and look at the lower right corner. There is some black blocks there with 3LUT processing.
But I think it won't be noticeable in actual movie scenes.

@cyberbeing - I was not able to see any real differences in actual movie scenes between those clipping modes. But I used the simple method.

[yesgrey]

Is there a reason why you removed the Out_Of_Gamut_Clipping option
Currently that option is not needed in yCMS.

Play my sample file
I can't download it. I only get a 1kB file.

[janos666]

@yesgrey - Try this link (http://rapidshare.com/files/396288093/Blueblanksample.mkv.html).

[yesgrey]

Try this link.
I got it, but I also need your configuration file for creating the 3DLUT.

[janos666]

I got it, but I also need your configuration file for creating the 3DLUT.
Last code area. (http://forum.doom9.org/showpost.php?p=1405988&postcount=53)

It's still recommended to not use the Grayscale_Measurements command until I fix what's wrong with it.
Will it affect the output_primaries command? I prefer to use that one as I use the VGA LUT to get gamma 2.2

[cyberbeing]

Is there a reason why you removed the Out_Of_Gamut_Clipping option which was in cr3dlut?Currently that option is not needed in yCMS.

Can you explain why you believe it is no longer needed? Doing color correction with a Perceptual rendering intent isn't automatically best for everything you know.

[yesgrey]

Doing color correction with a Perceptual rendering intent isn't automatically best for everything you know.
Using simple clipping isn't automatically best for everything you know, also. So, it has to be some kind of a mixed method, which yCMS is doing, hence the not inclusion of such an option.

[cyberbeing]

Using simple clipping isn't automatically best for everything you know, also.
'Simple clipping' taken literally would actually be Absolute Colorimetric, which you absolutely should not be doing. If by 'simple clipping' you actually mean Relative Colorimetric, then you are correct, which is why you would optimally need two different LUTs. One Perceptual and one Relative Colorimetric, depending on the content. At least that is how it is in the photography ICC color profile world.

So, it has to be some kind of a mixed method, which yCMS is doing, hence the not inclusion of such an option.
If you are compressing the gamut to preserve out-of-gamut gradients (which may not even matter), you are using a Perceptual method. This results in tone/hue color shifts of all colors which originally fell within the destination color space. This is usually the preferred method if your source has a lot of detail which falls out-of-gamut. If there is just one stray color which is way out-of-gamut, Perceptual can really mess up all your colors.

If you are not compressing the gamut and instead mapping out-of-gamut colors to the closest color in your destination color space, you are using Relative colorimetric. The goal of this method is to keep the original colors which were in-gamut in your destination color space unchanged. This is usually the preferred method if your source detail is mostly in-gamut. The goal is to preserve original colors whenever possible, which is not possible using a Perceptual method.

I don't really see how a mixed method is possible without two different LUTs or intervention of the video renderer. If you would explain what your mixed method was doing, that might help.

If a color is out-of-gamut, does yCMS do?

If if a particular color exists in both source and destination color space, what does yCMS do?

[yesgrey]

If a color is out-of-gamut, does yCMS do?
yCMS is not compressing the color gamut. All colors that lay in the destination gamut are untouched, it only changes the colors that lay outside the color gamut. yCMS can use a mixed method because it calculates all possible color combinations, and changes only the problematic ones.

[racerxnet]

I was wondering if a lut file could be created from the information from the panel manufacture. I copied the info and if someone could help I would appreciate it. CHI MEI LCD PANEL

Color Chromaticity


Red R x 0.632 -
R y 0.324 –

Green G x 0.273 -
G y 0.591 –

Blue B x 0.144 -
B y 0.068 –

White W x 0.280 -
W y 0.285

Color Gamut Min 68 Max 72

Thanks,

MAK

[yesgrey]

I was wondering if a lut file could be created from the information from the panel manufacture.
Add this line to your configurationFile:
Gamut_Measurements 0.632 0.324 0.273 0.591 0.144 0.068 0.280 0.285

Though, don't forget that the ideal situation would be measuring the primaries, because those indicated in the panel might not be accurate enough. However, it might give you a more accurate image than not using any correction at all.

Let us know how it worked.

[cyberbeing]

yCMS is not compressing the color gamut. All colors that lay in the destination gamut are untouched, it only changes the colors that lay outside the color gamut. yCMS can use a mixed method because it calculates all possible color combinations, and changes only the problematic ones.

So what type of 'changes' are being made to out-of-gamut colors?

You can:
A) Clip them (remove completely)
B) Move all out-of-gamut colors to the closet reproducible tone with no way to distinguish the out-of-gamut tones from your in-gamut tones. (multiple colors on the edge of the destination gamut represented as a single color)
C) Move all out-of-gamut colors to the destination gamut in a way so they are distinguishable from each other and produce smooth gradients (compress the gamut).
D) ????

[flanger216]

I'm still trying to stay afloat in all this colorimetry theory, but I'm hitting a conceptual dead-end:

I was under the impression that chromaticity primaries were an 'immutable' property of your display --- that is, you can tweak color and hue and gain settings as much as you like, but only a true CMS could actually alter the xy coordinates of your display's primaries. However, when I plot my TV's primaries to the CIE chart in HCFR, and then mess with the display settings, it quite clearly affects the shape and accuracy of the triangle on the CIE chart. In other words, my tweaks are affecting the chromaticity primaries, as reported in HCFR. Hue, color, gain, bias and temperature all affect the readings --- some quite severely.

My best attempt at wrapping my brain around this is the following: there are two sets of primaries --- let's call them the 'native' primaries and the 'gamut' primaries --- and the former refers to the full color gamut of which your display is capable, and the latter refers to the color gamut that ultimately results from your display settings (color temp, bias, gain, hue, etc.). HCFR intrinsically can only measure the 'gamut' primaries, because it must take its readings at the end of the display-chain, after the TV has performed its own post-processing.

Is this remotely accurate? Or am I still hopelessly confused? Most importantly, when and how should one measure the primaries for use in yCMS? As an extreme example, if I turn the 'color' control all the way down, the TV renders a black-and-white image, and HCFR would 'measure' the primaries as forming a curved line instead of a triangle at all. But this isn't really true, right? Turning the color saturation all the way down doesn't actually shift the color primaries into a linear curve... I imagine it merely distorts the measurements, not the 'true' chromaticity values of the display. So... for the purposes of using yCMS, should I measure the primaries at factory defaults, or after display calibration? Or am I doing this wrong? Is there some other method to calculate 'native' primaries?

Again, apologies... I'm usually semi-successful at figuring this stuff out, but colorimetry and CMSes are boiling my brains :eek:

[cyberlolo]

I'm still trying to stay afloat in all this colorimetry theory, but I'm hitting a conceptual dead-end:

I was under the impression that chromaticity primaries were an 'immutable' property of your display --- that is, you can tweak color and hue and gain settings as much as you like, but only a true CMS could actually alter the xy coordinates of your display's primaries. However, when I plot my TV's primaries to the CIE chart in HCFR, and then mess with the display settings, it quite clearly affects the shape and accuracy of the triangle on the CIE chart. In other words, my tweaks are affecting the chromaticity primaries, as reported in HCFR. Hue, color, gain, bias and temperature all affect the readings --- some quite severely.

My best attempt at wrapping my brain around this is the following: there are two sets of primaries --- let's call them the 'native' primaries and the 'gamut' primaries --- and the former refers to the full color gamut of which your display is capable, and the latter refers to the color gamut that ultimately results from your display settings (color temp, bias, gain, hue, etc.). HCFR intrinsically can only measure the 'gamut' primaries, because it must take its readings at the end of the display-chain, after the TV has performed its own post-processing.

Is this remotely accurate? Or am I still hopelessly confused? Most importantly, when and how should one measure the primaries for use in yCMS? As an extreme example, if I turn the 'color' control all the way down, the TV renders a black-and-white image, and HCFR would 'measure' the primaries as forming a curved line instead of a triangle at all. But this isn't really true, right? Turning the color saturation all the way down doesn't actually shift the color primaries into a linear curve... I imagine it merely distorts the measurements, not the 'true' chromaticity values of the display. So... for the purposes of using yCMS, should I measure the primaries at factory defaults, or after display calibration? Or am I doing this wrong? Is there some other method to calculate 'native' primaries?

Again, apologies... I'm usually semi-successful at figuring this stuff out, but colorimetry and CMSes are boiling my brains :eek:

I'm in the same boat.

[yesgrey]

So what type of 'changes' are being made to out-of-gamut colors?
Not A), not B), not exactly C). So I would say it's D)...

So... for the purposes of using yCMS, should I measure the primaries at factory defaults, or after display calibration?
I don't have yet the definitive answer for that. Furthermore, it might be the case that it will depend on the display type.
The main goal is the user setting the brightness and the contrast and let yCMS calibrate all the rest, but yCMS it's still a bit far from that...

After I correct the current problems with the Grayscale_Measurements command, I will post some simple instructions, but now, I need to keep my focus on yCMS.;)

[cyberbeing]

Not A), not B), not exactly C). So I would say it's D)...

So in other words you don't want to share what you are doing...

[naomatrix]

I have an LCD monitor is calibrated program Atrise Lutcurve and I watch movies through MPC-HC + madVR. Look it very good. I also tried to use parameters color gamut of my display, that I have received from computer program - Monitor Asset Maneger via EDID, my tinctures such

# Parameters by Monitor Asset Maneger
# Default color space ...... Non-sRGB
# Display gamma ............ 2.20
# Red chromaticity ......... Rx 0,640 - Ry 0,334
# Green chromaticity ....... Gx 0,285 - Gy 0,599
# Blue chromaticity ........ Bx 0,153 - By 0,076
# White point (default ).... Wx 0,313 - Wy 0,328

I ordered a template string

Gamut_Measurements 0.640 0.334 0.285 0.599 0.153 0.076 0.313 0.328

and made the files 3DLUt, but I do not see any difference between the image without gamut correction and with correction. Where should I look at and whether there is some objective method of comparing images. Is it possible to make in yCMS use of parameters gamut through EDID automatically.
Sorry for my english I'm from Ukraine

[yesgrey]

So in other words you don't want to share what you are doing...
Please don't take it personally, but until yCMS be more stable and less bug affected I prefer to not discuss publicly some aspects of it. I consider it solely as some kind of protection...;)
Furthermore, I haven't yet implemented some of my ideas. The current clipping is only slightly better than the other two available modes...

[yesgrey]

but I do not see any difference between the image without gamut correction and with correction.
The differences are more evident when the display gamut differs more from the source one, especially when it's wider, which isn't your case. In your case, the coordinates are so similar to the HD ones that you might not be able to detect any differences with real world images, probably only with some test patterns, where you could compare the primaries colors.
If you don't have any test patterns, go here (http://www.avsforum.com/avs-vb/showthread.php?t=948496) and get them on the first post. Play the 100% color video and you should be able to detect some differences.

Is it possible to make in yCMS use of parameters gamut through EDID automatically.
I don't know if that will ever be added, because the reliability of that info might not be very high...

[janos666]

Most importantly, when and how should one measure the primaries for use in yCMS?

There are three important components in your display:
- CCFL or LED back-light which has it's own color spectrum and it's own color temperature (and max/min luminance).
- LCD TFT panel with it's R, G, B pixels (made with color filters)
- (digital) driver/controller panel(s).

They are intended to match with various design parameters which can be a standard (like Rec709, sRGB, ect...) or any custom design. But they will be slightly unique (one by one) and they will change in time uniquely. (This is the reason why you need a colorimeter. You shouldn't think those instruments are perfect, but they are usually more than enough.)

The combination of the back-light and the TFT panel will determine the native characteristics of your display.
You have different options to push your display closer to the desired standard characteristics:
- It can be done with the internal electronic controllers, fully or partially.
- You can use software calibration, like VGA LUT or yCMS, ect.
- They can be used together.

Your possibilities will be limited by the supported hardware calibration features. Some professional displays will allow you to upload your 3D LUTs (made by an automated software) and make a complete hardware calibration. Some display will let you change a few things only (nothing like 2D LUT or IRE list for gamma or sliders for huye and saturation, but luminance and contrast only...)

There is no universal rule here but the general suggestion that you should change any possible setup in your hardware settings first and fine-tune it with software calibration. (Of course, you should omit any hardware features if you find them defective. And this applies to software bugs as well.)

And the basic idea behind this calibration:
- You have ** output characteristics but you want ## like ones. - You know the desired ## and you can measure the representative values of the ** state.
- You can make a matrix with math functions or pre-calculated tables of any possible values to manipulate your input signal to get ## through your ** output distortion.

Of course, the number of the lost color tones will be (nonlinearly) scaled by the distance between your display's native characteristics and the desired standard.
But this is another hardware factor. We usually have 8 bit/color materials and some displays will support higher bit depth. For example it will process the 10 bit input signal with 12 bit accuracy for 10 bit visualization, so there can be some room for image manipulation without losing details. But the other side is when you have 8 bit input with 8 bit processing and 6+2 bit visualization (like 6 bit TN or c-PVA panels with dithering) and you are far from the standard.

yCMS creates 16 bit 3DLUTs but MadVR will convert it back to 8 bit with dithering (I do not know but may be fake 10 bit quality is a good estimation - but there will be some dithering noise as a side effect...). But this number can be increased in the future with deepcolor support.

So, this is a deep hole, filled by eternal questions, desinformations, and a lot of shit. But the achievable result is much better than it was without calibration.

And to answer to your question (if you didn't figured it out already): You should use the measures which you make after the hardware or VGA LUT calibration. (Because that is your current display characteristic.)

You can see hexagonal CIE diagrams when you measure the primaries and secondaries after you manipulated the primaries only. This is not a standard behavior for HDTVs or consumer PC monitors. May be this function can be used for better CMYK simulation (which is used by printers).

[cyberlolo]

But how are the chromaticity primaries (Rx Ry Gx Gy Bx By Wx Wy) measured? Yesterday, an ISF certified calibrator came home to calibrate my KRP-500A, and he didn't know how to get those values.

He used his calibration equipment, and he saw that in Pure mode, using Bumtious' settings, my set was already perfectly calibrated. He only had to tweak the color temperature to reach 6500K, but nothing else. And then, I showed him the yCMS manual and asked him to give me the chromaticity coordinates of my TV so I can enter them to create a custom 3dlut, but he didn't know how to get those values.

Any help here, please?

[Mark_A_W]

Measure Primaries with HCFR and export values to a spreadsheet. Is this what you want?

Measure Red Green Blue Yellow Cyan Magenta
X 14.10174 9.465929 4.771986 22.703403 14.206526 18.559078
Y 7.40095 20.656126 2.066542 27.544523 22.373522 9.33258
Z 0.631434 5.138814 25.99736 5.800269 31.580687 26.514742
R 34.007427 -3.639539 -0.67371 28.340027 -4.099868 32.5783
G 0.242164 29.789465 0.331876 29.909027 29.515242 0.621179
B -0.05774 1.744957 27.324909 1.775425 29.609224 27.156624
Rc 7359 1014 280 7929 1312 7477
Gc 911 6691 943 7526 7520 1842
Bc 317 2897 5284 3202 8234 5577


My friend is an ISF Calibrator, he went to the US to do the course. He only did it because he needed it as a "qualification" as a professional calibrator.

He said the course is a complete joke. It's like calibration for 5 year olds. So being an "ISF Calibrator" as such is almost meaningless, it bears no reference to their actual competence.

[cyberlolo]

Not exactly. What I want is something like this (values are not mine) for my display:

# Red chromaticity ......... Rx 0,640 - Ry 0,334
# Green chromaticity ....... Gx 0,285 - Gy 0,599
# Blue chromaticity ........ Bx 0,153 - By 0,076
# White point (default ).... Wx 0,313 - Wy 0,328

So with that info I can create a 3dlut with this line:

Gamut_Measurements 0.640 0.334 0.285 0.599 0.153 0.076 0.313 0.328

So my question is: how can I get this values that belong to my display?

[Mark_A_W]

Is this closer? I just picked xyY instead of RGB. (Sorry the columns get all mixed up).

Measure Red Green Blue Yellow Cyan Magenta White
x 0.637104 0.268454 0.145328 0.405069 0.208427 0.341119 0.316547
y 0.334368 0.585809 0.062935 0.491444 0.328246 0.171535 0.330533
Y 7.40095 20.656125 2.066542 27.544523 22.373521 9.33258 29.550847
delta E 9.6 15.6 5.3 8.7 11.6 17.1
delta xy 0.50% 3.50% 0.60% 2.00% 1.60% 0.027
delta luma 17.80% -2.30% -3.10% 0.50% -3.80% 10.90%

[cyberlolo]

Yes, Mark, I think you got it! With that info, your values are:

# Red chromaticity ......... Rx 0.637 - Ry 0,334
# Green chromaticity ....... Gx 0.268 - Gy 0.585
# Blue chromaticity ........ Bx 0.145 - By 0.062
# White point (default ).... Wx 0.316 - Wy 0.330

And now, can you PLEASE explain me how have you done it?

[Mark_A_W]

With my DIY HCFR probe, and the HCFR software.

There are cheap probes you can buy instead of build....probably cheaper than your ISF calibration..

http://www.homecinema-fr.com/colorimetre/index_en.php


I think I just answered half of my questions to Yesgrey myself (the other part being "how to get a custom gamma curve").

[Mark_A_W]

Oh, and these aren't my "real" measurements. These numbers come from some quick and dirty measurements on my 24" Sony CRT monitor, not my projector.


But I know how now :)

Just need to break out the tripod and measure the projector again (it's been a while).


Actually, my colour filtered CRT projector is very close to Rec 709. The reds a bit more saturated, but I kinda like that. I will try the Gamut cropping with the 3DLUT, but I will need a new videocard, the 2600XT stutters on bluray with the 3DLUT enabled.

[cyberlolo]

Cheers Mark, you've been of great help to me. I think I'll call the calibrator to see if he can come home again to use his probe with HCFR and get the values. Thank you!

[Mark_A_W]

If he saved the measurements, then he already has the values. He just has to find the values in xyY format, like I did.

[yesgrey]

Not exactly. What I want is something like this (values are not mine) for my display:
# Red chromaticity ......... Rx 0,640 - Ry 0,334
# Green chromaticity ....... Gx 0,285 - Gy 0,599
# Blue chromaticity ........ Bx 0,153 - By 0,076
# White point (default ).... Wx 0,313 - Wy 0,328

You're right, the manual is not clear enough. I will add that the coordinates must be in xyY format. Sorry for the trouble.

(the other part being "how to get a custom gamma curve").
What do you mean with that?
(1) How to measure your display's gamma curve or
(2) How to use yCMS to let you create your favorite gamma curve

[Mark_A_W]

"(2) How to use yCMS to let you create your favorite gamma curve "

There is an application on AVSforum called Video Equalizer.

http://www.avsforum.com/avs-vb/showthread.php?t=1042160
http://archive2.avsforum.com/avs-vb/showthread.php?t=777353

You can drag the curves around to create a custom gamma curve. All together, or one colour at a time.

It's used to create a custom gamma curve, but you have to run it each time you boot to load the custom gamma curve (a big limitation).


If this kind of interface, combined with the ability to call series of standard gamma curves (say 2.2, 2.3, etc), was combined with a colourimeter greyscale measurement, and yCMS, then we'd have a closed-loop custom gamma curve solution.

Combine this with the gamut correction, and it's perfect (isn't it?). You get a correct gamut and your desired gamma curve (standard or custom).

Mark

[yesgrey]

"(2) How to use yCMS to let you create your favorite gamma curve "
That's on my todo list too. ;)

To be honest, with the Grayscale_Measurements command it's already possible to do it, but it's not very user friendly... I already have some ideas on how to do it in a more friendly way, but we'll discuss it after I release the next yCMS version.

[Mark_A_W]

VideoEqualizer looks like this:

http://dl.dropbox.com/u/1372034/VideoEqualizer.jpg


And it kinda does "standard" gamma curves (LH lower sliders), but the numbers use the PC style numbers (which are backwards), not the "video" way of describing gamma.

[janos666]

But how are the chromaticity primaries (Rx Ry Gx Gy Bx By Wx Wy) measured? Yesterday, an ISF certified calibrator came home to calibrate my KRP-500A, and he didn't know how to get those values.

LOL. If that happened as I imagine, I would say: "Stop! Do not touch anything! Leave my house now, please." :p

ISF means nothing in my country. We just use the instruments. There are some barbarians who want to sell their half job for big price but others have EyeOne or ColorMunky and they know what they are doing and their price is good. (I bought an own colorimeter because I would like to test different settings. And I could do a favor for friends, as they did other favors for me in exchange, so it was not an expensive instrument at all.)

[flanger216]

My experiences with ISF 'technicians' have also been subpar at best. Not as bad as the yokels at the cable company, mind you --- I once had some cable tech, standing in my apartment, staring at a huge purple 60hz hum-bar wobbling down my TV, and he actually argued that the problem was caused by my speakers. He was, of course, referring to the magnetically shielded speakers that were sitting five feet from my LCD screen. I could only stare at him gape-jawed and politely observe that I'm pretty sure magnetic distortion looks nothing like that, that I'm pretty sure there are no magnetic fields in an LCD screen that could become improperly biased, and that I'm pretty sure it's just a ground loop caused by the oxidized bird's nest of coax cabling installed haphazardly on the roof of the apartment building. He stared at me like I was speaking Chinese. I swear to god, the cable guy didn't know what a freaking ground loop is.

So yeah, teaching yourself is the way to go :)

And thanks for the write-up on colorimetry, janos666... extremely helpful stuff!

P.S. I almost forgot the capper to the story: eventually I got so fed up that I went out and bought a big roll of coax cable, went up to the roof in the middle of the night, ripped out the cable company's mess and just reinstalled the whole stupid thing myself --- and I actually bothered to loop the cabling properly and (gasp!) put it in an enclosure so it wouldn't get rained on. Finally, no more ground loop. A few days later I overheard a few neighbors wondering if the cable company had done something to make their TVs look better :rolleyes:

[sepheas]

hello,

I would like to have more information about the custom gamma curve. In fact, I really don't understand the values : lv av pv threshold ?

The only thing I understood is pv= 1/gamma.

Is there a way to create a custom gamma curve with something like videoequalizer and then save it with the values ( lv/av/ap/threshold)

I mean, to adjust it graphically and then catch the values to paste into ycms.

sorry for my english, if there's errors