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Basic Guide to Color Calibration using a CMS (updated and enhanced) - Page 56

post #1651 of 1936
Quote:
Originally Posted by basement View Post

Hello, I'm relatively new to calibration and was wondering if someone could suggest what I'm doing wrong. I'm using the i1 with hcfr on a jvc rs10. I'm basically looking to calibrate for greyscale, contrast, brightness, and trying to target gamma for 2.2.

I don't seem to have any trouble with greyscale, but brightness and gamma is a problem. I've set white level to the jvc default which gives me acceptable luminance. Then, following the objective black level setting procedure I display a 10 ire pattern (Tom's posted images) and adjust Y to .65% of Y at 100 IRE. I adjust for greyscale then do a measurement. Greyscale measures fine and luminance tracks the 2.22 curve. However, when I check the brightness setting against a pluge pattern (avshd basic settings), it turns out the brightness setting is set to about six clicks too low. When I view a video, there's a clear loss of detail in dark areas. The picture is clearly better with the brightness set using the subjective pluge pattern.

I then do a new measurement with the new brightness setting, greyscale is still good, but hcfr now averages 1.9 and gamma no longer tracks flat across the scale. It tracks linearly from 10 to 30% then starts to drop off, until at 90% the gamma reading is about 1.1.

So I seem to be in a situation where my settings measure well but the black level seems wrong. When black level is set using the pluge it looks better, but gives me a gamma that tracks to a non-linear lower gamma average.

I'm not sure if it's a factor or not but I'm calibrating against a computer source using kmplayer. I haven't been able to find postings from others with like circumstances.

Thanks in advance. Any help appreciated.

Set black level by eye using the pluge pattern. Are you re-measuring your 100% white window after changing the brightness setting with the pluge pattern? Set your settings, take a 100% reading, then measure 0-90%. If that doesn't help, make sure your contrast isn't set too high. You might be clipping white.

I don't know about this "kmplayer," but computer sources are generally crap. Not saying yours is, but it could be the problem.
post #1652 of 1936
Thread Starter 
Please re-read the instructions carefully for setting black level at the beginning of this thread. If the gamma is not a standard 2.22, the objective method won't work.

The pluge pattern is the gold standard. Use the objective method only refine it. The AVSHD test pattern is so precise that no refinement is needed.

Quote:
Originally Posted by basement View Post

Hello, I'm relatively new to calibration and was wondering if someone could suggest what I'm doing wrong. I'm using the i1 with hcfr on a jvc rs10. I'm basically looking to calibrate for greyscale, contrast, brightness, and trying to target gamma for 2.2.

I don't seem to have any trouble with greyscale, but brightness and gamma is a problem. I've set white level to the jvc default which gives me acceptable luminance. Then, following the objective black level setting procedure I display a 10 ire pattern (Tom's posted images) and adjust Y to .65% of Y at 100 IRE. I adjust for greyscale then do a measurement. Greyscale measures fine and luminance tracks the 2.22 curve. However, when I check the brightness setting against a pluge pattern (avshd basic settings), it turns out the brightness setting is set to about six clicks too low. When I view a video, there's a clear loss of detail in dark areas. The picture is clearly better with the brightness set using the subjective pluge pattern.

I then do a new measurement with the new brightness setting, greyscale is still good, but hcfr now averages 1.9 and gamma no longer tracks flat across the scale. It tracks linearly from 10 to 30% then starts to drop off, until at 90% the gamma reading is about 1.1.

So I seem to be in a situation where my settings measure well but the black level seems wrong. When black level is set using the pluge it looks better, but gives me a gamma that tracks to a non-linear lower gamma average.

I'm not sure if it's a factor or not but I'm calibrating against a computer source using kmplayer. I haven't been able to find postings from others with like circumstances.

Thanks in advance. Any help appreciated.
post #1653 of 1936
Quote:
Originally Posted by TomHuffman View Post

Please re-read the instructions carefully for setting black level at the beginning of this thread. If the gamma is not a standard 2.22, the objective method won't work.

The pluge pattern is the gold standard. Use the objective method only refine it. The AVSHD test pattern is so precise that no refinement is needed.

Tom, When setting Contrast ( i.e., white level) with the S&M disk, do you set it to resolve the white bars all the way up to 255, or to you set it (higher) to resolve them only up to 235?
post #1654 of 1936
Quote:
Originally Posted by millerwill View Post

Tom, When setting Contrast ( i.e., white level) with the S&M disk, do you set it to resolve the white bars all the way up to 255, or to you set it (higher) to resolve them only up to 235?

Assuming you can get your display to distinguish it's a personal choice. The only people I know of that have looked closely at this found no significant deliberate content above 235 (they looked at discs and DI sources). All of it could be explained by poor scaling (i.e. it was all ringing). There is a reason to go to 254 (which I forget so how important can it be) and a reason to stop at 235 (better contrast ratio).
post #1655 of 1936
Thread Starter 
The amount of program material this high is infinitesimally small, if it exists at all. I would not sacrifice a significant amount of peak output to maintain performance in an area that has little bearing on image quality.
post #1656 of 1936
Quote:
Originally Posted by TomHuffman View Post

The amount of program material this high is infinitesimally small, if it exists at all. I would not sacrifice a significant amount of peak output to maintain performance in an area that has little bearing on image quality.

OK, thanks to you and bodosom for the replies. What you say is what I had thought was preferable, but S&M on the guide for their disc says to set it to resolve the bars up to 255, which led to my confusion and question.
post #1657 of 1936
Quote:
Originally Posted by millerwill View Post

... S&M on the guide for their disc says to set it to resolve the bars up to 255 ...

While I would never speak for Stacey or Don I suspect they're making some assumptions. If you're using a "typical" display (LCD) then you probably have the headroom to waste a bit of peak output. Some folks (PJ/plasma owners) need to be a bit more parsimonious with their limited output budget.
post #1658 of 1936
Quote:
Originally Posted by rfbrown94 View Post

Set black level by eye using the pluge pattern. Are you re-measuring your 100% white window after changing the brightness setting with the pluge pattern? Set your settings, take a 100% reading, then measure 0-90%. If that doesn't help, make sure your contrast isn't set too high. You might be clipping white.

I don't know about this "kmplayer," but computer sources are generally crap. Not saying yours is, but it could be the problem.

Ok. From your responses, and Tom's, I think I see the problem with my process. I should adjust using pluge then re-measure 100% and verify at 10%.

If after doing this, and it still does not track to 2.2, then the display gamma is not set correctly, or my contrast is too high, clipping luminance at higher ire.
post #1659 of 1936
Thread Starter 
Quote:
Originally Posted by basement View Post

If after doing this, and it still does not track to 2.2, then the display gamma is not set correctly, or my contrast is too high, clipping luminance at higher ire.

Or your display's gamma is not a natural 2.22 and cannot be fixed. This is not uncommon.
post #1660 of 1936
Quote:
Originally Posted by TomHuffman View Post

Or your display's gamma is not a natural 2.22 and cannot be fixed. This is not uncommon.

I spent a bit more time on this. Taking a cue from comments about computer software video players, I tried calibrating the display using different software players and found that luminance does not track very well. Prior to the software players, I calibrated a Panasonic bluray player and easily had it adjusted properly for greyscale and with luminance following the 2.22 reference.

It turns out kmplayer was the best of the three I had. It tracks fairly well between 20 and 60, then from 70 to 90, luminance drops off - looking like contrast was set too high. I lowered contrast and got the same relative result. I played around a little bit with video card software settings rather than player settings. With no knowledge on what the settings do, gamma response can be adjusted but the results were not satisfactory. On a side note, even with changes in gamma, greyscale was always good, so colour was satisfactory. The htpc forum may have some answers.

Anyhow, thanks to all for your help.
post #1661 of 1936
Hi Tom,

I notice in your introduction, regarding using blue filter for Plasma displays can result in a wholly inaccurate colour level, when using SMPTE colour bars. I've noticed this, as the SMPTE bars are not 'widows', it causes a deviation. The only method one can use, for a plasma display, is the 'windows' colour patterns, using 'blue only' mode.

There are no colour patterns for a plasma display that will allow the use of a blue filter, not that I know of? Unless someone knows better?

Regards

Delphi
post #1662 of 1936
Thread Starter 
I don't know if it is all plasmas. I just noticed it on a couple of plasmas. I also don't know if the CAUSE of the problem is the need for window patterns. It may or may not be. However, I am skeptical about this explanation because it would apply equally to CRTs and I have not noticed the problem there.

In any case, I would always recommend direct measurement instead of filters and color bars. Even inexpensive colorimeters are reasonably accurate reading luminance, which is all that is necessary to set Color. Tint requires an accurate reading of hue, which cheap colorimeters are less adept at. Still, even here, I would expect the tolerances to be well within reason.

Quote:
Originally Posted by delphiplasma View Post

I notice in your introduction, regarding using blue filter for Plasma displays can result in a wholly inaccurate colour level, when using SMPTE colour bars. I've noticed this, as the SMPTE bars are not 'widows', it causes a deviation. The only method one can use, for a plasma display, is the 'windows' colour patterns, using 'blue only' mode.

There are no colour patterns for a plasma display that will allow the use of a blue filter, not that I know of? Unless someone knows better?
post #1663 of 1936
Hi,

I come to this conclusion after measurements on Plasma displays with 'Blue only mode'.

The results are very different when choosing the size of the pattern, this would indicate to me that the results would be the same for 'blue filters'. I assume that this is the draw in current due to the 'White level'? However, you are quite right when you speak of CRT measurements not seemingly being affected by the size of the pattern?

Of course, as you say, direct measurement is the best way to do the measurement, although, as the direct measurement isn't 100%, I find it best to go through all the methods to get the best balance?

Not sure if you would agree?

Thanks

Delphi
post #1664 of 1936
Why is this thread no longer a sticky?
post #1665 of 1936
Quote:
Originally Posted by Joelc View Post

Why is this thread no longer a sticky?

I hope this thread being unstickied has nothing to do w/AVS becoming a reseller of Calman.

Tom Huffman has been helping fellow AVSers for a long time and I thought his thread being stickied was a nice recognition of that.
post #1666 of 1936
It's now included in the stickies under "Links to this forums popular threads" making it and the others, ummmm, somewhat sticky.
post #1667 of 1936
Tom

At the start of this thread for the brightness adjustment you stated to adjust the luminance of a 10% white test pattern to .6% of the luminance of a 100% white pattern.

So that is multiply by .006?? Correct??
post #1668 of 1936
Thread Starter 
Quote:
Originally Posted by mechman25 View Post

At the start of this thread for the brightness adjustment you stated to adjust the luminance of a 10% white test pattern to .6% of the luminance of a 100% white pattern.

So that is multiply by .006?? Correct??

Yes, but I also wrote:

Since I originally wrote this, the AVSHD disc has released a very advanced version of the pluge pattern that allows the user to set black level with perfect accuracy by eye alone. If you have access to this disc, then use it. Because it is so precise, it makes using objective measurements to set brightness unnecessary.

post #1669 of 1936
Quote:
Originally Posted by TomHuffman View Post
Yes, but I also wrote:

Since I originally wrote this, the AVSHD disc has released a very advanced version of the pluge pattern that allows the user to set black level with perfect accuracy by eye alone. If you have access to this disc, then use it. Because it is so precise, it makes using objective measurements to set brightness unnecessary.

Which pattern, Tom and where on the disk?

thx

bob
post #1670 of 1936
Quote:
Originally Posted by spongebob View Post
Which pattern, Tom and where on the disk?

thx

bob
first basic pattern, "Black Clipping Pattern" AVSHD709
post #1671 of 1936
Quote:
Originally Posted by PlasmaPZ80U View Post

first basic pattern, "Black Clipping Pattern" AVSHD709

That has never worked on my Elite Pro-101FD. Even cranking brightness all the way up just washes out the picture.

What about the near black windows? Which of those should be visible? I usually have to go to 4% or so.


thx

bob
post #1672 of 1936
From the first post:

Of these definitions, only the xy coordinates for the primary colors and white point are absolute. The secondary colors and luminance values are DERIVED from the primaries and the white point. If your primary colors measure according to these standards, then this list correctly states the proper specifications for brightness and secondary hue/saturation. However, with a different set of primaries, you would want to shoot for a slightly different set of brightness and secondary hue/saturation targets. The math required to figure out these relationships is too complicated to go into here, but good calibration software should take all of this into account.

Tom can you elaborate a bit on the part I bolded above? Many of us, if not most, have "different set of primaries". I have struggled to know what the "different set of brightness and secondary hue/saturation targets" to aim for.

I have CalMAN and ColorHCFR and don't really see how either of these gives me the "different" targets, (unless you're suggesting to randomly change things looking for lower dE values?)

Thank you.
post #1673 of 1936
Thanks Tom for the reply

Yes I have this disc, even downloaded the version 2 disc.
This pattern was very easy to use.

I recently bought a colorometer and have done some calibrations on my Plasma and LCD.

Greyscale coming out fine on both.
LCD coming out fine but the color gaumet on the plasma is way off on the green, so I am just trying to figure out if I am doing something wrong.

I am going to try some more calibrations on something other then the custom mode and warm2 settings I was using.
post #1674 of 1936
Thread Starter 
Quote:
Originally Posted by kjgarrison View Post

However, with a different set of primaries, you would want to shoot for a slightly different set of brightness and secondary hue/saturation targets. The math required to figure out these relationships is too complicated to go into here, but good calibration software should take all of this into account.

Tom can you elaborate a bit on the part I bolded above? Many of us, if not most, have "different set of primaries". I have struggled to know what the "different set of brightness and secondary hue/saturation targets" to aim for.

I have CalMAN and ColorHCFR and don't really see how either of these gives me the "different" targets, (unless you're suggesting to randomly change things looking for lower dE values?)

ColorHCFR doesn't offer this ability. I don't know if CalMan does or not. ChromaPure does.

It is certainly not random. The same math that yields the secondary and brightness targets for the standard gamuts results in different targets for non-standard gamuts.
post #1675 of 1936
Thread Starter 
Quote:
Originally Posted by mechman25 View Post

LCD coming out fine but the color gaumet on the plasma is way off on the green, so I am just trying to figure out if I am doing something wrong.

This is a very common reaction. The simple fact is that many commercial displays are just not designed with accuracy in mind.
post #1676 of 1936
Once I do a couple more calibrations I will post results.

Can there be hardware problems that cause one color to go way off?
post #1677 of 1936
Thread Starter 
Quote:
Originally Posted by mechman25 View Post

Once I do a couple more calibrations I will post results.

Can there be hardware problems that cause one color to go way off?

Sure, but the most likely hardware problem is the design of the display.
post #1678 of 1936
Quote:
Originally Posted by spongebob View Post

That has never worked on my Elite Pro-101FD. Even cranking brightness all the way up just washes out the picture.

9G Kuro monitors clip BTB and WTW in CE space unless you enable DRE. The easiest way to verify this is to switch to IT space (RGB:0-255) with the input in CE space. You'll see all the bars flashing unless clipping is happening elsewhere. Of course if the input signal is YCC the colors will be wrong but the bars will still be visible.
post #1679 of 1936
For adjusting contrast only, would just the light meter and a test pattern work?
post #1680 of 1936
Quote:
Originally Posted by marc55 View Post

For adjusting contrast only, would just the light meter and a test pattern work?

All you need is a test pattern and your eyes.
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