The Official ChromaPure thread - Page 129

Anyone care to comment on the post calibration color gamut shown here jan 22 post-cal color gamut1.jpg 74k .jpg file or the ACM Chromacity garph shown here ACM Chormacity.jpg 21k .jpg file

I think they are looking like they are supposed to look. Some errors on blue and yellow but I think that stems from teh fact I can't back any more red out of my Blue.

How about the Blue luminance is that showing a high error I need to work on?

Your dE's are lower than 1, all lower than humanly visible. Even if you could get them lower, you wouldn't be able to see a difference. The only thing you could do is see what makes the colors track better, using 75 or 100% patterns.

Not a techy person but I think the maths of the YCbCr part of Rec 709 means that green is measured after taking the blue (Cb) and red (Cr) away from the Y (Luminance), so if you adjust green you effectively change the gamma as well.

At least that's what happens if I change green.

Others may perhaps correct my understanding of the process.

Green is oversaturated with too much luminance. To desaturate, you add equal amounts of the other two primaries. To low luminance you lower the amount of the same color (green).

Good deal. Thanks again.

How about the Luminance chart in this Quick Report? It shows a 5.5% error (I think) for blue. Is this something that needs adjustment? The dE on blue isn't high....
Edited by rocketman9 - 1/23/13 at 9:52pm

I should have read it before. Really good information!

Hello. What is one of the best ways to go about doing gamma. Last night I did multiple adjustments to the gamma my target is 2.22. Everytime I noticed when using the Gamma module with the 100% white value in place and setting my gamma at 2.22 during the adjustments that when I go to take a post greyscale run my gamma in the 90% white drops to 2.16. 80% and 70% drops as well. What I am trying to get at is what is the best approach in calibrating the gamma when you adjust one interval but then it could effect another. Say adjust 90 and then 80 then check 90? any tips to get it more linear and near target specially at 70, 80, 90 % white.

What display? Assuming 10 point grayscale, try adjusting 90% with the 80% control, 80% with the 70% control, etc.

It's a Samsung plasma. PN51D6500.

You are apparently doing a gamma run and then measuring 90% while you adjust with the 90% controls. It probably changes 100% so when you reset and do another run 100% now has a different luminance and 90% is now incorrect.

1 .Measure 90%
2. Adjust with the 80% controls and see if that helps.

You mean after first adjusting 90% as good as possible with the 90% controls?

And when you move on to measuring and adjusting 80%, won't the required changes to the 80% and 70% controls change 90% measurement? And on, and on .... like Dominoes .... Won't subsequent adjustments all the way down ripple back all the way to 100%?

The thing folks need to realize about 10 point (or 20 point) adjustments is:

• Often (usually) the center point of a given adjustment is NOT at the stated point (a "80%" adjustment) may well be at an different point (like 89%).
• The "width" of the adjustment may be relatively wide - so there is interaction with adjacent points.

I noticed it also. After 10pt adjustment, simply take 5% readings. There can be huge differencies. Advice is, make small steps and always check previous interval.

No. First set 100%. Then measure 90% but try adjusting 90% with the 80% controls. Every TV is different so you have to see what works and what doesn't - part of why some calibrations can be very time consuming.

The "domino theory" is part of what convinced me to be a Marine in Viet Nam. Seriously, on nearly every display I've seen, once you get 100 - 80% where you want them the rest of the luminance points are not nearly as disruptive.

Remember too that 80-90-100% relative gammas are very sensitive to probe and display repeatability (ratios of small numbers). A 1% change in either 90% luminance relative to 100% or vice-versa will shift gamma by 0.1 In reality the gamma values at these levels can be pretty unstable and are considerably less important than the lower stimulus values.

Zoyd, if I read you right the real key to calibrating grayscale is to get 10-20-30% right? I know that is putting words in your mouth so I am not saying that you said that, I am asking "Did I interpret what you said correctly?"

If that is the case, how can we get that right, given that many meters don't operate as accurately at low stimulus levels (I think)?

Not exactly, I was talking about gamma calibration (Y) which all meters can do reliably down to 10%. The point being that for gamma the upper end, say 80% and 90% is pretty irrelevant perceptually and can also be hard to pin down as people have pointed out. It doesn't matter if the 90% level is 2.2 or 2.3. On the other hand greyscale is very important to nail down at every level your meter is capable of.

Is there a trial version of Chromapure available? I am trying to decide if I want to go HCFR, Calman or Chromapure.

Any comments on the relative strengths and weaknesses? What made all you Chromapure users pick it?

Hello,

I have a problem with my i1 Display PRO meter. It is very hard (and long) to read high IRE like 80%.
Chromapure "doesn't answer" for a long time, then gives me a wrong reading. I must redo the measure several times.

I have my meter connected to my PC via another USB cable.
I'm using a French version of Windows 7, does it matter too ?

Thanks for the help.
Remi.

Novice calibrator here -- picked up a CP Standard/Display 3 Pro package from Tom recently and spent a few hours last night making several rounds of adjustments on my Panasonic 60ST50. Not nearly as intimidating as I first thought it would be. I'd be interested in any opinions of my inaugural results.





While the overall light output is on the low side (~22.5 fL), our viewing area is typically dimly lit, and the image really pops.

Any suggestions for subsequent button-pressing sessions? (And yes, there will be more -- this is nearly as much fun as watching a good blu-ray!)

You should be getting more light than 22.5 ft-L. What Picture mode are you in? Try Custom. Everything else looks good.

By "another USB cable" do you mean a USB extender? This is probably too long. It shouldn't be over 3 meters.

Contact Customer Support and we can give you a copy with a simulated meter. You can also view the Demos on our web page.

Yes. And then Press OK several times as prompted.

I am in Custom -- it's the only mode on this model that offers access to its "Pro" settings' two-point grayscale adjustment. I'll crank up the output to 30+ fL next time I play with it.

I know there are more granular adjustments in the service menu -- anyone here have any experience working in the SM on recent Panasonic plasmas? I'm wondering if it might be worth trying to improve those primary and secondary numbers, or if I should leave well enough alone.

Thanks. Yes I'm using a 3 meter USB extension.
May that's what cause the problem.

And sorry to ask it again :
But some users are using Small APL patterns to calibrate their Panasonic Plasma 2012 (ST50 in my case).
Do you still advise the Windows patterns only ?

Thank you.

Small windows are fine. What is not fine is full fields.

I also use a usb extension, but with an amplifier build into the plug thats on the cord. I have no problems at all. Make sure your wire is not curled up in a bundle though, the cord has to be free. I have had malfunctions on other equipment with that (scanner)

I just listened to Scott Wilkinson response to manufacturer's boast about their displays having a much wider gamut. Scott correctly points out that content (broadcast and Blu-ray) are mastered to a narrower gamut than what wide gamut displays are capable of, so he asks, what good is a wide gamut display? The manufacturer's response is that the content was originally filmed using a much wider gamut, which was shrunk only when transferred to Blu-ray or mastered for broadcast. The wide gamut display, the argument goes, merely restores these missing colors.

Let me explain why this is nonsense. In the first place this is nothing new. Manufacturers have been offering wide gamut displays for a long time. The original JVC LCoS projector, the RS1, had an extremely wide gamut. This is an old argument, but manufacturers keep recycling it as a way of convincing gullible consumers to purchase their products.

Second, while it is true that content is originally filmed using a wider gamut, most of the colors we see don't take advantage of the extra colors. Skin tones, trees, grass, sky are all composed of colors that fall well within the Rec. 709 HD standard. Only a relatively small percentage of the colors are lost when the gamut is shrunk to fit the HD standard.

Third, and most importantly, when remapping colors from a wide gamut source to a narrower gamut medium, the ONLY colors that are affected are those small number that are outside the HD gamut. The rest of the colors--the vast majority--stay the same. Think for a moment why this is true. If a skin tone naturally falls well within the HD gamut, you wouldn't want to change that color when remapping wide gamut source material to HD. That would visibly distort the skin tone. Only the relatively few very saturated colors will be remapped to fall within the HD boundary.

This explains why attempting to restore the original gamut by playing HD content on a wide gamut display is a bad idea. What the wide gamut display does is oversaturate ALL colors--including the skin tones I mentioned in the previous example. The display has no way of distinguishing between those colors that were compressed during the mastering process and those that weren't, so it indiscriminately increases the saturation of all of the colors.

BTW, there is one practical advantage to a wide gamut display for some users. If you have a good color management system, then it is useful to have as a starting point oversaturated colors that can then be desaturated to the correct HD standards. Other than this, manufacturer claims about wide gamut displays are unhelpful marketing hype that should be ignored.
Edited by TomHuffman - 2/7/13 at 11:42am