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# Grayscale variances - different patterns, plasma calibration - Page 8

Quote:
Originally Posted by anta1974

If I'm doing my own patterns, I do them in 16:9?
Area 2% ?

I don't have a plasma to test, but looking at the ramp luminance that Zoyd posted I have to figure the procedure would result in a window that's considerably larger than 2% area on his display. Assuming a 2% window is on a black background, the math just doesn't seem to work for the ramp measure from Zoyd's post. On the other hand larger windows is where you tend to get into problems with variation on plasma. The ramp measurement from Zoyd is rather high, since a 50% gray field on a perfect display is roughly 18%-22% luminance from a theoretical perspective. Even if I had a plasma, I'm not sure if I would consider it worth my time to try tracking down a window size that matched.
Edited by alluringreality - 2/26/13 at 5:16pm

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Quote:
Originally Posted by alluringreality

I don't have a plasma to test, but looking at the ramp luminance that Zoyd posted I have to figure the procedure would result in a window that's considerably larger than 2% area on his display. Assuming a 2% window is on a black background, the math just doesn't seem to work for the ramp measure from Zoyd's post. On the other hand larger windows is where you tend to get into problems with variation on plasma. The ramp measurement from Zoyd is rather high, since a 50% gray field on a perfect display is roughly 18%-22% luminance from a theoretical perspective. Even if I had a plasma, I'm not sure if I would consider it worth my time to try tracking down a window size that matched.

So I went back and updated the previous post with the proper locations of the AVSHD APL patterns and also remeasured the linear ramp this time without trying to do a spatial average. The linear ramp now measures 17.2% of peak luminance which is closer to what one would expect.

Regarding the "ramp method". If I follow the procedure described the size of a 100% stimulus window that best matches the ramp luminance at the probe position is 5% area. I still think this is too small based on the data above, the only thing it accomplishes is to ensure that the 100% pattern generates an average screen luminance (as measured over a partial screen by the way) that a linear ramp generates. This isn't tied to any physics that I can tell.
Edited by zoyd - 2/26/13 at 7:28pm
Quote:
Originally Posted by zoyd

Regarding the "ramp method". If I follow the procedure described the size of a 100% stimulus window that best matches the ramp luminance at the probe position is 5% area.

I think the procedure says to use a 50% gray window for matching the ramp measurement, so I'm guessing you're looking at a window over 10% area.
Quote:
Originally Posted by Light Illusion

> Then make a calibration patch window with 50% white and sized it to get a similar Luma reading with the probe in the same place.
Quote:
Originally Posted by alluringreality

Quote:
Originally Posted by zoyd

Regarding the "ramp method". If I follow the procedure described the size of a 100% stimulus window that best matches the ramp luminance at the probe position is 5% area.

I think the procedure says to use a 50% gray window for matching the ramp measurement, so I'm guessing you're looking at a window over 10% area.
Quote:
Originally Posted by Light Illusion

> Then make a calibration patch window with 50% white and sized it to get a similar Luma reading with the probe in the same place.

How is that possible? I'm measuring the equivalent of 50% white with the gray ramp already. So the window would have to fill the probe FOV meaning the entire display.
I can't make any sense of the procedure regardless if it's 50% or 100% gray. It would make a lot more sense from a mathematical standpoint if "50% white" meant 100% gray, but I don't know what 50% would represent in that case. All I really know is that Charles Poynton considers it unacceptable to cross the meanings of luma and luminance.
Except that gray is just white that isn't as bright as 100% white.

The problem is that your eyes are relative. The brightest grey in the room becomes white. Hang a black disk where you can illuminate it so that the only thing illuminated is the black disk. It will look white.
Surely,the Spectracal guys have the answer to this mystery (secret pattern size) for greycale variances,since they work hand in hand with Panny engineers.

Look at the pattern size here @29 sec. in Derek's VT30 demo video...It looks like about a 6-7% size pattern size...
Quote:
Originally Posted by PeterLewis

Surely,the Spectracal guys have the answer to this mystery (secret pattern size) for greycale variances,since they work hand in hand with Panny engineers.

Look at the pattern size here @29 sec. in Derek's VT30 demo video...It looks like about a 6-7% size pattern size...

Interesting video, little off topic but what is required to do an autocal on a Vt50, have calman control, meter, what is the pattern source ?
Quote:
Originally Posted by chunon

Interesting video, little off topic but what is required to do an autocal on a Vt50, have calman control, meter, what is the pattern source ?

Its not off topic.

Everyone here is trying to find a magic pattern size to control abl variances and right here under our nose is a Spectacal pro calibrator that works with Panny engineers so the pattern size he is using in his demo video must be the correct one that many of us have been looking for to use on Panasonic 30/50 series.

BTW...does anyone know what size pattern Derek is using in the demo?
That's just the default window size for the QD780 that was being used.

We don't have any better information than Stacy Spears used to create his new equal energy patterns or what's being discussed in this thread.

We are paying attention though and will continue to add patterns to add support for APL patterns into CalMAN as they become available.
Edited by sotti - 2/27/13 at 4:58pm
Quote:
Originally Posted by sotti

That's just the default window size for the QD780 that was being used.

We don't have any better information that what Stacy Spears used to create his new equal energy patterns or what's being discussed in this thread.

We are paying attention though and will continue to add patterns to add support for APL patterns into CalMAN as they become available.

Thanks for the feedback and good to know you guys are working to get patterns to combat that finicky abl monster..
Yellowish bright areas( like white backgrounds,bright areas) look good on tvs too counter the overly blue lighting in my opinion.I know some shows lighting is yellow/red already.

Does anyone have an opinion on how having a slight yellow tinge too the darker parts of screen looks ? I have not tried calibrating for a Yellow tinge with darker areas much.The blue lighting used on a lot(not all) of shows have bluer blacks.
Edited by Vic12345 - 3/2/13 at 10:41pm
Quote:
Originally Posted by ndaa75

These patterns certainly make sense on the face of it. I've recently been experimenting with 1% windows on a Panasonic with pretty good results visually so will be interesting to do a comparison with 1% APL windows.
Will likely try between 20 and 30% to see what impact they have, if any.

Well tried the 1% APL from the GCD disk on my VT30 - compared to custom 1% windows the 1% APL looked slightly washed out, most likely due to 20% stim needing a significant gamma asjustment to bring it in line with 2.2 (1% windows needed no such adjustment). Furthermore colours also looked a little washed out, will stick with 1% for the time being until I find an alternative that works well with a Panasonic.
I have a question regarding pattern size I'd like to ask.
I have a VT50EU and a lumagen mini 3d. I use the patterns on the lumagen for calibration, but there are 3 sizes, Full field, medium windows and small windows. What I noticed is that on the small windows my contrast setting is a lot lower to get to 35 ftl then it is with the medium patterns. I's a good 7 clicks difference. I am guessing that with the medium patterns the ABL kicks in and I have to crank the contrast up to get the correct light output. But it has left me to wonder which one is the "correct" setting, though on an ABL screen there might not be a "correct" setting. If I set contrast with a medium patttern, and complete the rest of the calibration with small patterns, would that be wrong?
I personally don't target 35 fL,

I run the plasma as hard as it can go, but without clipping all the way to 255. If you want it spot on the numbers you'd need to set contrast with some sort of APL pattern ( even then it will very by picture level). You can always drop down to using a disc to set light output and then go back to using the mini pattern generator for the rest of the process.

When it comes to contrast it's only wrong if it clips too hard or hurts your eyes. The happy middle ground is pretty wide.
Exactly my issue. Measure 100% white a 12%,15% or 5% or 6% window yields a different number for cd/m².
Simply make sure you do not clip white and that it does not hurt your eyes. Also no discoloration is a requirement.

But it would nonetheless be nice to be able to pour this into a number. If it is too dim it would be hart to tell by how much.
Quote:
Originally Posted by Wouter73

I have a question regarding pattern size I'd like to ask.
I have a VT50EU and a lumagen mini 3d. I use the patterns on the lumagen for calibration, but there are 3 sizes, Full field, medium windows and small windows. What I noticed is that on the small windows my contrast setting is a lot lower to get to 35 ftl then it is with the medium patterns. I's a good 7 clicks difference. I am guessing that with the medium patterns the ABL kicks in and I have to crank the contrast up to get the correct light output. But it has left me to wonder which one is the "correct" setting, though on an ABL screen there might not be a "correct" setting. If I set contrast with a medium patttern, and complete the rest of the calibration with small patterns, would that be wrong?

Surely your VT50 being European, is brightness limited as my VT30 is?
I know its a different model but i set my contrast as per sotti, cant be choosy when you have a limited amount of lum to play with.
Yes it is limited, but only in the isf presets. That is why I got a lumagen mini, I can now fully calibrate all my presets, and the others are not capped on the vt50eu
Not exactly true. Cinema mode has the same limit as ISF mode, 80 nits. And THX cinema is limited to 100 nits. Only normal, THX bright and game have about 150-160 nits.
Quote:
Originally Posted by Wouter73

Yes it is limited, but only in the isf presets. That is why I got a lumagen mini, I can now fully calibrate all my presets, and the others are not capped on the vt50eu
Of course.....
Quote:
Originally Posted by DrFaxe

Not exactly true. Cinema mode has the same limit as ISF mode, 80 nits. And THX cinema is limited to 100 nits. Only normal, THX bright and game have about 150-160 nits.

Yes indeed, I stand corrected. I did notice this when I was searching for the "best" preset for calibration. Which one would you recommend?
I used the THX cinema mode for some reasons. Thinking image processing should be as low as possible, but as much as needed for good PQ.
Light output of ~100 nits is enough for me, as I only watch in a dark room.
RGB level and gamma was quite good before calibration, so no big corrections needs to be done
by the Radiance (also got a mini 3D). Gamut actually was very good so I skipped the color cube and only do 21pt. greyscale calibration.
For sure I also run the cube and compared the image, as I didn't see a difference in color I decided to use greyscale calibration only as the gamma was better.
See http://www.avsforum.com/t/1423111/calman-5-release-notes-and-discussion/960#post_22936623
Quote:
Originally Posted by DrFaxe

I used the THX cinema mode for some reasons. Thinking image processing should be as low as possible, but as much as needed for good PQ.
Light output of ~100 nits is enough for me, as I only watch in a dark room.
RGB level and gamma was quite good before calibration, so no big corrections needs to be done
by the Radiance (also got a mini 3D). Gamut actually was very good so I skipped the color cube and only do 21pt. greyscale calibration.
For sure I also run the cube and compared the image, as I didn't see a difference in color I decided to use greyscale calibration only as the gamma was better.
See http://www.avsforum.com/t/1423111/calman-5-release-notes-and-discussion/960#post_22936623

What size pattern do you use on your VT50?
I used the large window pattern from the Radiance, which are ~11% size.
How does that work out on the VT50? Any issues with gamma alignment?
Quote:
Originally Posted by DrFaxe

I used the large window pattern from the Radiance, which are ~11% size.

Do you also happen to know the size of the small patterns on the mini?
Quote:
Originally Posted by Wouter73

Do you also happen to know the size of the small patterns on the mini?

Small are approx 1.5% on the Radiance I believe
actually I'm very happy with the results and the PQ. Regarding the gamma, this drove me nuts in the past and honest I don't care much about now.
Why? because I accepted that is not possible to get a flat gamma on a plamsa and after reading ALL related post here in the forum, Doug Blackburn's postings regarding gamma and pattern size made the most sense to me. Thanks Doug!
I use a power gamma of 2.2 which looks visibly best on my TV, and with the "good" MLL of the THX mode I don't have issues with black crush and good details near black.
To me it doesn't make sense anymore to think about some minor better measurings of gamma (as the TVs ABL will "destroy" everything) if I'm very satisfied with the PQ.

Small pattern size, if I remember right, is 1,65%,
So what do you do, just greyscale and gamut, and leave gamma alone?

What I am wondering about, the standard gamma becomes a LOT brighter at higher IRE. Is it possible that Panasonic sort of compensates for the ABL by cranking the luminance up at higher IRE's?
I just calibrate greyscale and gamma no gamut. If You see my results from the posted link there was nearly no benefit in calibrating gamut too.

regarding gamma, You mean the precalibrated gamma of the THX cinema mode? On my TV gamma on the higher IRE was min. 2.0. What's your's as You write a LOT?

"Is it possible that Panasonic sort of compensates for the ABL by cranking the luminance up at higher IRE's?"

that's what I thought too, but I'm not that pro to give the right answer.

and with the default settings gamma is flat.

Edited by DrFaxe - 3/6/13 at 6:54am
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