Grayscale variances - different patterns, plasma calibration - Page 5

Here's what I came up with for a 6.5% size pattern @ 50% brightness on a black background.


6.5% size @ 50% brightnessRGB126c.jpg 152k .jpg file
Edited by JimP - 12/12/12 at 9:09am

(219/2) + 16 = 125.5

Then it depends on which way you round. In CalMAN we round up to 126.
Edited by sotti - 12/11/12 at 9:18am

if you use Calman 5 just activate "Pattern Change Prompts" in the "Source Settings", click the read button and Calman shows You the RGB values. No need to calculate.
I just did so and rebuild the 75% color APL Large Pattern of the AVSHD709 BD in Photoshop just to verify whether my approach is right. Window sizes are exactly the same. Than created an mp4 file with Sony Vegas Pro using REC709 in the project settings. But after comparing the measurements of the original AVSHD pattern with my own, luminace, saturation and hue differs. Seems not to be that easy creating your own pattern disc. Any hint?

Hey,

I'm new to this great forum and just read this thread. As a DIY calibrator with about 1 year experience, and still learning, i'm always interested optimizing my VT50EU. Just wondering if someone figured out the correct pattern size for Panasonic VT30/VT50? Did some pattern from 2% to 20% (area) and 50% stimulus (RGB126/126/126) for testing. If anyone still interested:
window.zip 153k .zip file

The Excel sheet column A/B/C/D show the sizes, rest was just for calculation. Other file format or windows sizes needed please let me know.

best regards

Please clarify?

If different pattern size is required on gcd please let me know

Visca,thanks for all your hard work on the GCD disc.

Would it be possible for you instead of using 1% pattern windows to use a 6.5% window sized patterns on GCD similar to what THX uses...The 6.5% window will give many of us 2011 Panny GT/VT30 a more accurate calibration.Thanks..

I don't mean to discourage you, but I don't think you'll find a magic window size for a European VT30. It's very, very tough to get the NA VT30, when set to panel brightness low as the EU models are, to not show posterization. PB mid seems less prone to it, and it's possible with a lot of perseverance to get most of the posterization out when calibrated in mid.

Chad B.

On the North American VT50s, have you found a particular window size that works best????

I get beautiful results with no banding using conventional 5% windows.

I have a samsung pn51d6500 what window size do you recommend i use. I tried 10% APL from GCD. My gamma ended up being 2.21 avg.

When you say "conventional", I take that to mean that it's not an APL pattern, right?

Is this available on any of the disc that are floating around or did you have to make up your own set of patterns?

I haven't tried the GCD APL windows on a PN-D series yet, but from what I've read in the GCD thread it sounds like those patterns would do a great job.

The PN-E series ABL has surprising characteristics in that conventional 25% windows give a higher light output in comparison to 10% windows. This is the opposite of what you would expect if you're used to Kuro-like behavior, where larger window sizes reduce light output and round off the gamma at the high end, which is much more common.

If a plasma has a 10 point adjustment and if it has the more conventional ABL behavior, my opinion is that you should use either very small (my preference is in the 3-7% range) conventional windows that do not trigger the ABL (with contrast calibrated for no clipping or discoloration) or use APL windows that will load the ABL circuitry in an evenly controlled manner. What you don't want to do in that situation is use large conventional windows and try to compensate for the rounded off gamma with the 10 point adjustment.

If a plasma has unconventional ABL behavior as the PN-E series appears to, then larger conventional windows would most likely give better results than very small ones, with the APL windows also being a viable option.

You can test your PN-D series behavior by putting it in movie mode with cell light max, contrast high (near clipping point), and take a run with small windows and then large ones. If the large window results in a rounded gamma and less light output, then very small windows or APL windows is what I would recommend. If it shows PN-E like behavior, then medium to large windows (10-18%) or APL windows are what I would recommend.

Correct. My pattern generators have variable window sizes when used with CalMAN. I believe the CalMAN CalPC pattern generator does also.

I'll make some 4% (approx) .PNG window patterns for you and post them here.

If you're trying to author an image to video one possible complication might be Vegas converting the image to video levels. You don't say what levels you were expecting to represent black and white, but most likely an option to author images to video would cause a conversion to video levels. If your image was already in video levels, a modification intended to convert to video levels would mess things up.

To avoid moving between computer levels and video levels, we create video directly from images. Then we author that video to Blu-ray. That way we don't have to worry about how the authoring software tries to convert images to video levels, and it also allows us to use video levels that are darker than black or brighter than white.

The following two posts generally include our authoring process and the images we use to create video. Our images are setup to represent video levels, so that way we can show shades darker than black or brighter than white. Since the linked images are already setup for video levels, feeding them into a Blu-ray authoring program that tries to convert images to video levels would result in incorrect levels.

http://www.avsforum.com/avs-vb/showthread.php?p=16837914#post16837914
http://www.avsforum.com/t/948496/avs-hd-709-blu-ray-mp4-calibration/3390#post_22305141
Edited by alluringreality - 12/13/12 at 6:43pm

Here they are:
http://www.avsforum.com/t/1445226/chad-bs-custom-test-patterns

Dear alluringreality,

first of all thank You very much for the detailed explanation and the links which are a complete how to. Indeed this will help me creating my custom pattern disc.

That's clear the issue why my results messed up. I expect video levels, used Photoshop and video levels (black 16, white 235) for the images. Saved as .psd and imported directly into Sony Vegas.
Just to make sure, You used "MeGUI" for the MP4 files also? Would MPEG-4 AVC (x264) be the correct format?
Want to make MP4 files first because it's much more convenient for testing purposel instead of mastering blu-ray and burning discs.

Did You use 5% windows also for color?

Both the MP4 and Blu-ray files from our project were encoded using x264 and MeGUI. I haven't followed how x264 settings may have changed since our video was encoded, but the settings I used for 1080p video encoding are included at http://www.avsforum.com/t/948496/avs-hd-709-blu-ray-mp4-calibration/3180#post_21567091 Generally I don't follow this forum, yet if you run into encoding issues visca blaugrana may be able to help with the general process.

Hi Chad,
On plasma, Adusting WB control too much will likely cause more banding? The True Cinema preset' color temperature on my ST50 is ~ 5500, so I ended up did quite a bit of adjustment to get correct D65 and 2.2 gamma; using 10% ABL pattern. I do not notice any serious banding but not very sure about it.

I have a few questions regarding:

1. with the probe covering all the screen. What is meant here? Using a "non-contact" probe? or?

2. if not, then are you moving back from the display to get the Ypeak? Or, if in contact, moving to the part that is the brightest or just trying to pin the 50% middle and match it to a pattern size that provides a similar reading?

going to give it a try, but thougt I needed to understand a little better so I don't chase ghost too much. Sounds like an interesting method. What are some others?

Regards,
T.

here are the steps in detail as i understood them:

(1) Establishing Full Screen Probe Distance

> put up 100% white patch FULL SCREEN, establish probe distance from screen so u read the entire screen, moving the probe back and forward (towards / away from the screen), once peak luma value drops you are too far from the screen

(2) Get Peak Luma Greyscale

> with the probe in the same established position from step 1, put up greyscale ramp FULL SCREEN and note the peak luma value the reading gives you

(3) Establish Pattern Size

> with the probe in the same established position from step 1, put up 100% white patch and change the patch size to match the peak luma value from step 2

(4) Establishing Probe Distance For Custom Pattern Size

> move the probe closer to the screen (closer to the patch size established in step 3) until you get a peak reading, that means the probe is just reading the patch itself, nothing around it


==> that will be the final position of the probe along with that patch size


I tried this out yesterday night and on my VT50 plasma and it did not work... the i1D3 I used as a colorimeter is so unstable in it's readings (maybe it is the VT50 plasma ABL causing issues here) that the values u read (peak luma) change constantly...

if I would leave the probe in one position for 1-5 minutes (just for testing), the peak luma value would continuously start to DROP although the plasma is constantly displaying a 100% white and the probe was not moved...

when u try to establish the position of the probe in (1) where you compare peak luma values, this probe behavior makes this impossible as you move the probe around comparing bogus values to each other...

If anybody else tests this, please let me know your findings...

Thanks.

- M

Chad thanks for the tip about the e series and different window sizes issues( I wondered what size window to use).im Fortunate too see it as I don't look in the calibrating section often.That one tip will save me one heck of a lot of time and headaches.On certain middle to bright scenes with bright patches on it I'm getting all sorts of overbright brights in the bright patches and colors not right in the patches.I have a soft bright picture settings to avoid black crush...i dont have a meter.Hopefully this helps me.
Edited by Vic12345 - 12/28/12 at 3:06am

Dear Steve!


Is a version with contact measurement ?
You can come up with something for contact measurements ?

with respect, Andrei.
Edited by anta1974 - 2/2/13 at 6:03am

It means that the probe or color meter is not touching or in "contact" with the screen use of a tripod is required. Contact mode is the oposite.

Not sure what you would get with this scenerio, but you could use a full ramp, as used above (which I think is intended to allow both a full rastered image, without tripping the ABL). Take some readings at some random points from dark to light (or use a ramp with known values) and do an average in contact mode, then use that data to figure out the "patch" and similar luma? Just babbling here, but it will probably accomplish a similar thing with a little more work. my 0.o2

Very thanx!
I did something like this as you said!
Once I made ​​smarter- I measured full fields (10% 20% 30% 40% 50% 60% 70% 80% 90% 100%) and received the average brightness!
got a very good result
my Panasonic VT50E
luma 21.51 cd/m2
Pattern 4.5% - 21.572 cd/m2
5% - 21.310 cd/m2

It seems to me that we need to be more precise when we talk about gamma with respect to plasma and ABL. I think of it in terms of static gamma and dynamic gamma.

At any single moment in time, the image on the screen has more and less luminous areas. Static gamma is the input stimulus versus output luminance curve produced by the display at that moment in time. Because the effect of ABL at that instant is constant, it seems to me to be perfectly calibratable and the truly important definition of gamma from an image quality standpoint.

There is also dynamic gamma which is the curve produced (in the extreme case) by increasing from a fully black screen to a fully white screen. This is the gamma we can't truly calibrate because the amount of ABL in effect changes over time and is also affected by the size of the patterns used in performing the calibration. I just don't see this as being as important to image quality as static gamma. After all, when I'm outside and the sun goes behind a cloud for a moment and the world's ABL kicks in I don't start complaining about how bad the scenery looks.

My conclusion is therefore that I want my gamma to be flat when measured at a single level of ABL effect. If I can pick windows that are small enough that ABL has no (or almost no) effect, or if I use APL windows, and achieve a nice flat gamma I think that's the best quality picture. Of course, if ABL isn't implemented perfectly, which I would expect to be the case, things might drift for different levels of ABL activity. So I conjecture that it would be best to calibrate gamma using APL windows where the APL matches the average image luminance of normal content. Much like the idea of using 75% saturated colors when calibrating CMS.

The problem with the normal way we calibrate gamma, using ordinary windows, is that the amount of ABL effect is not constant and increases as we get to the higher stimulus levels. The gamma calibration is being performed on a moving target.
Roy