this is a calibration workflow example using the latest options in Lightspace and other workflow tools available nowadays.
TV set is a Panasonic 65VT60 NA.
Meter is a K10-A with spectro offset.
Lumagen pattern generatorVT60 PRE-PROFILE DISPLAY SETUP
Turned all internal processing off. Used Ted's disc to check which CMS controls introduce problems. Dial in Brightness via LI's brightness calibration image - those patches are 1 lsb each. We also used Ted's disc to confirm the Lumagen (used as a pattern generator) was outputting correct levels.
You would now setup Contrast the usual way, but for the VT60 I will go into into detail here as these sets have Gamma issues - I have confirmed this with multiple other VT60 owners - if you don't own a VT60 you may consider skipping this section:
The VT60 has very inconsistent Gamma, especially in the 85-100% brightness region, which can result in very wild gamma spikes (seen on a Gamma log-log graph) that can go either direction, towards a higher or lower Gamma value. I've seen as low as 0.97 and as high as 3.6 - sometimes (depending on Gamma and contrast setting) the display shows a double spike, it goes down to 1.0 and then up to 3.0 all within the last 6% brt, ergo 94-100%.
It does not matter which settings are used: Pro mode or custom, ISF Night or Day, I’ve set Contrast to everything between 50 and 100, I’ve tried all color temperatures and all Gamma pre-sets and a combination of them.
Standard 10pt or even 21pt Greyscale runs don't really show the issue as the 5% brightness spacing is too large. You might see problems at 90 and/or 95% but then again the internal VT60 gamma controls are 10pt only anyways, so way too coarse to fix or address these issues. You need a GS evaluation with 101 pts, ergo very tight spacing of 1% to really see what is going on.
Here are 3 gamma graphs of 3 different VT60's (all NA) - all profiles are 101 pt GS runs, so u see what is really going on:
We're using the Lightspace Profile Reporter
tool here to directly evaluate LS profiles - in the case of the 3 gamma graphs: 101 pt Greyscale only profiles. This workflow allows me to stay in LS and use all of the professional tools that LS offers that other solutions do not offer (active LUT etc, see later in the workflow) w/o having to switch to another solution to get a profile evluation (and then deal with other issues). This speeds things up quite a bit.
I ran a 101pt greyscale only in Lightspace (using a custom color patch set that only contains 101pt Greyscale points), then checked for drastic Gamma spikes, then adjusted Gamma / Contrast setting and or used Gamma CMS control. Did this a few times, trying to bring the drastic spikes somewhat under control. I will address / improve Gamma later on in the workflow, but the better the pre-profile setup the easier the adjustments will be later on.CREATE COLOR PATCH SEQUENCE FOR PROFILING
All patch sets (profiling & validation) were created using the Custom Color Patch Sequence Generator.
The profiling patch set that was used in this calibration is a larger color patch sequence. Before Lightspace allowed the import of custom color patch sequences we've been using 21^3 patch sequences with 9,261 points. With a fast meter the time frame is easily doable.
This patch set was targeted to have equal or less points than a 21^3 but with improved performance, as in that it "scans" / profiles the gamut more evenly and more throrough, providing more relevant and conclusive information to the color engine. This set has 9,137 points (so slightly less than a 21^3) but with better profile point coverage and distribution than a standard grid sequence including a 101 point Greyscale (and all corresponding R, G, B reads).
This is a very straightforward patch set that I used for this calibration, easy to understand, you can easily decrease the point count (profile size) if you like. For other calibrations, I used a an more refined variation of it. Regarding patch set size: if you cut the point count too much your results be inferior. The more accurate and conclusive data you provide to the color engine, the better the results will be.
The patch set was created with HSB parameters, easily understandable and very easy to control. Here are the patch set parameters:
As you can see - in this specific patch set - I am sampling every 2nd integer hue value, so out of 360 hues, we are sampling 180 hues. That is a tight spacing of just 2 hue degrees and will make sure we don't leave out too many hues.
For Brightness levels, we are sampling a total of 30 (!) brightness level, a 21^3 (with more profile points) samples just 21 brt levels. As you can see the brightness levels are grouped in packs of 10 brt levels and changed for each hue, this way we keep the the total point count lower BUT we are sampling 30 brt levels in just 4 hue dgrees !
So over a very narrow span of just 4 hue degrees (!) our color engine will get LOTS of data of that parts of the gamut, example:
0 deg is sampled with these brt levels: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100
2 deg is sampled with these brt levels: 6, 15, 25, 33, 45, 54, 66, 75, 84, 95
4 deg is sampled with these brt levels: 23, 28, 36, 42, 48, 57, 63, 72, 78, 87
--> brt cycle starts again at 6 deg using these parameters
You can see how powerful this is, I can easily refine this patch set and even expand the brt level range without increasing the total profile point count ! So I could add another 10 unique brt levels for a total of 40 brt levels over a span of just 6 hue dregrees. Just keep in mind to find a balance between the hue span and the brt levels. Don't let the span get too wide with brt levels points that are "too far apart".
Also, note how the 3 brt level groups are stacked / spread to each other, they sit within the other groups spacing.
Saturation levels are relative to brightness, so each of these saturation levels are sampled for each or specific brightness levels. Again, because we want to get the most data from the gamut out of our patch set, we stack sat levels in groups. We are using 20 well spread sat levels in 4 groups. Similar to what we do with the brt levels we change the sat levels for the brightness levels with every other hue from our hue set.
brt levels @ 0 deg are sampled with these sat levels: 20, 40, 60, 80, 100
brt levels @ 2 deg are sampled with these sat levels: 10, 30, 50, 70, 90
brt levels @ 4 deg are sampled with these sat levels: 5, 25, 45, 65, 85
brt levels @ 6 deg are sampled with these sat levels: 15, 35, 55, 75, 95
Again, note how the 4 sat level groups are stacked / spread to each other, they sit within the other groups spacing.
So, summing up, over a narrow span of just 6 hue degrees we are sampling: 3 unique hues, 30 unique unique brt levels (with a total of 40 brt levels sampled) and 20 unique saturation levels - all nicely spaced to cover the region evenly.
Here's a visual evaluation of the patch set:
Take a note how evenly we distributed points, especially pushing enough data into the 25-75% brt and 25-75% sat range. We also arranged the patches to cycle between dark/bright to (try to) counteract ABL - note the Average patch brightness difference.DECREASING PATCH SET SIZE & FURTHER REFINEMENTS
To further refine this set, one could start to adjust the hue spacing depending on region, e.g. sample with wider spacing in dense gamut regions (--> green, blue) and with more narrow hue spacing in less dense regions (--> red). Just don't let the spacing get too wide. The further add more brt & sat levels and distribute them smartly. Example of different hue sampling depending on hue region:
To decrease the patch set size, there are lots of options:
For starters, one could decrease the brt levels and sat levels below 25% brt and above 80% brt, because the shadows and highlights contain less information. If your screen is inaccurate in the shadows (i.e. LCD backlight contamination) u don't need to waste your time there anyways. Same if your meter can't read low brt levels.
Or simply increase the hue spacing, e.g. sample every 3rd or 4th hue.
Or one could simply take out brt levels and sat levels in all brt levels. This will drastically reduce patch set size. Instead of 30 brt levels have 20 or 15, instead of 20 sat levels have 10 - OR - keep 30 brt and 20 sat levels but distribute them over a wider hue range... Lots of possibilities.
Alright, enough talk run the profile on the VT60. ;-)
Took ca. 3 hours with the K10 because we included a 0.75s extra delay to prevent temporary IR from the last color patch.
Then created LUT in LS targeting the standard Rec 709 Gamma 2.2.