BasICColor DISCUS Owners thread - Page 4 - AVS Forum | Home Theater Discussions And Reviews
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post #91 of 120 Old 03-26-2020, 08:27 AM
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Quote:
Originally Posted by dlinsley View Post
Tim, if you need specifics these are what I use with the Discus and i1pro2 (non-referral links to Amazon):
Amazon 7 port 4A hub
Tripp Lite 36ft USB2 extender
If you put the powered hub *after* the passive extension and make sure the power can deliver at least 500mA per port, you don't need an active extension. I use an Amazon basics extension before the hub and it works fine (although the i1pro2 will not pass some reflectance tests that way, but they are not needed for front projector calibration AFAIK and I have no issues in my calibration sessions).

At least 2A for 4 ports and 4A for 8 ports is what you need, as long as you don't do anything silly (for example putting a lot of non-powered hard drives in the same hub as the meters).

Personally I don't plug anything but the three meters in my 4-port powered USB 2.0 hub, and I don't use more than two meters at the same time.

If you can, it's always better to move the laptop/computer and use one of the computer's ports without any extension.

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Last edited by Manni01; 03-26-2020 at 09:18 AM.
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post #92 of 120 Old 03-26-2020, 09:45 AM
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Please note that the laser pointer in the Discus is offset from the centre of the measurement spot, with a parallax offset of something like 3cm.

And when comparing FOV spot sizes the manufacturer data is 'generic', as all probes have 'soft' edges to the measurement spot.

The only way to really 'verify' spot size (and position) is to use slow (manual) wipe of a wide white stripe on black.
As soon as the white stripe enters the spot measurement area the probe reading will start to increase above 'black'.
That process will have to be performed for left/right/top/bottom.

Obviously, the 'reading speed' of the probe will define the speed at which the white stripe can be moved.

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post #93 of 120 Old 03-26-2020, 10:04 AM
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Quote:
Originally Posted by Light Illusion View Post
Please note that the laser pointer in the Discus is offset from the centre of the measurement spot, with a parallax offset of something like 3cm.

And when comparing FOV spot sizes the manufacturer data is 'generic', as all probes have 'soft' edges to the measurement spot.

The only way to really 'verify' spot size (and position) is to use slow (manual) wipe of a wide white stripe on black.
As soon as the white stripe enters the spot measurement area the probe reading will start to increase above 'black'.
That process will have to be performed for left/right/top/bottom.

Obviously, the 'reading speed' of the probe will define the speed at which the white stripe can be moved.

Steve
Yes, we know all that, the 3cm off centre is even mentioned in Daryll's document. We're not sending a rocket to the moon, we're measuring patterns for a home-cinema set-up.

It's just that the data used by myself and others for years without issues was questioned by some.

You have provided useful data for the Discus, but without comparable data for the i1pro2 it doesn't really help, as we don't know exactly what you are measuring.

The whole point of Darryl's table was to provide data that was comparable, precisely because in most cases the manufacturers' data isn't.

I haven't experienced any issues following Darryl's measurements, training a Discus to an i1pro2 with half a dozen JVC projectors over close to a decade.

So until a reliable source (you would be one) provides an alternate set of data for at least the two meters discussed here (Discus and i1pro2), there is no way to compare.

I have zero motivation to take any of these measurements, given that I get excellent results with the values I have already suggested (2ft for i1pro2, 1ft for Discus or 3ft for i1pro2 and 2ft for Discus, or both Discus and i1pro2 at the same distance, provided the pattern is large enough, which should be the case with the meters at 1-2 ft, aimed the way I suggested, with 100% size patterns). Here, all of these provide repeatable, accurate results.

So if you can't provide the other half of the information, there is no point in questioning the data already available, or the methodology.

The day an alternate set of values is published, I'll happily compare results.

In the meantime, I'll keep doing what I've done for many, many years

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JVC Macro feature on Vertex/Vertex2/Integral2/Maestro

Last edited by Manni01; 03-26-2020 at 10:11 AM.
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post #94 of 120 Old 03-26-2020, 10:40 AM
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These are some profiling results I got with Ted's workflow.
Are those offsets in the norm for a Discus.

I come from an i1D3 and they were not so big.

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post #95 of 120 Old 03-26-2020, 10:51 AM
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As I said, set 100% white to D65 with the i1pro2 (within 1 dE 20000), make your profile following my advice including settings for each meters, then look at what you get with the Discus when the profile is applied. I use the white balance layout for this because it gives you peak white and RGB balance at 100%.

The brightness should be more or less identical, and the dE should be the same (under 1 dE 2000).

It's normal to have large corrections in the profiles because the Discus is significantly off in its default mode, but you should get the same readings from the profiled Discus at 100% stim as with the i1pro2.

If you get a large difference at 100% white, something is wrong in your profiles or methodology.

If you can't get 100% white to read properly, there is no point taking gamut readings, they will be wrong.

Only proceed with further measurements when you've got the first step right.

Of course I'm talking about profiles for your JVC. I have no idea about what you have to do for your OLED.

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Last edited by Manni01; 03-26-2020 at 11:22 AM.
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post #96 of 120 Old 03-26-2020, 11:08 AM
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Quote:
Originally Posted by Light Illusion View Post
@ 50cm = 8cm

With an aperture angle of 4.5 deg.
8 cm is in line with Darrell Bird’s numbers, but that would not correspond to 4.5 deg.
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post #97 of 120 Old 03-26-2020, 11:14 AM
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Quote:
Originally Posted by Dominic Chan View Post
8 cm is in line with Darrell Bird’s numbers, but that would not correspond to 4.5 deg.
I thought so myself initially, but unless I'm mistaken Darryl's numbers are in inches and Steve's numbers are in cms. The relative size is in line, but not the absolute values.

This is why I asked Steve to confirm what he was measuring (FWHM? TLT? Something else?) and to provide measurements of the same data for at least the i1pro2.

Otherwise his numbers are useless: Manufacturers' measurements can't be compared directly as often they don't measure the same thing.

We need, like Daryll did, measurements of the same data, in the same units, for at least two different meters (minimum Discus and i1pro2).

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Last edited by Manni01; 03-26-2020 at 11:23 AM.
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post #98 of 120 Old 03-26-2020, 12:07 PM
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Quote:
Originally Posted by Manni01 View Post
I thought so myself initially, but unless I'm mistaken Darryl's numbers are in inches and Steve's numbers are in cms. The relative size is in line, but not the absolute values.
At 50 cm distance Darrell’s number would be about 9 cm (by interpolation), vs 8 cm from Steve.

However, Darrell quoted 11 deg, which is consistent with the diameters. Steve quoted 4.5 deg (unless that’s half the total angle).

Last edited by Dominic Chan; 03-26-2020 at 01:38 PM.
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post #99 of 120 Old 03-26-2020, 12:20 PM
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Quote:
Originally Posted by Dominic Chan View Post
At 50 cm distance Darrell’s number would be about 9 cm (by interpolation), vs 8 cm from Steve.

However, Darrell quoted 11 deg, which is consistent with the diameters. Steve quoted 4.5 deg.
Until we get two sets of data for two meters done with the same methodology, any data is pointless.

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post #100 of 120 Old 03-26-2020, 01:35 PM
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Quote:
Originally Posted by Manni01 View Post
Until we get two sets of data for two meters done with the same methodology, any data is pointless.
i1Pro aperture (and presumably i1Pro2) has a plateau shape fall-off whereas the Discus has a Gaussian fall-off, so I don’t know what would be considered “done with the same methodology”. Darrell’s figures are probably as good as any.

In any case, unless the projector is super non-uniform I don’t see how it would matter. And if the projector is that non-uniform, having only a few inches in the centre calibrated to 100.00% accuracy doesn’t mean much when looking at the whole picture.

Last edited by Dominic Chan; 03-26-2020 at 01:45 PM.
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post #101 of 120 Old 03-26-2020, 02:00 PM
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Quote:
Originally Posted by Dominic Chan View Post
i1Pro aperture (and presumably i1Pro2) has a plateau shape fall-off whereas the Discus has a Gaussian fall-off, so I don’t know what would be considered “done with the same methodology”. Darrell’s figures are probably as good as any.

In any case, unless the projector is super non-uniform I don’t see how it would matter. And if the projector is that non-uniform, having only a few inches in the centre calibrated to 100.00% accuracy doesn’t mean much when looking at the whole picture.
This is what I've been saying all along.

I'm happy with Darryl's table, but some here are questioning its validity.

All I'm saying is that if anyone is questioning Darryl's work, it's pointless to post one set of data about one meter.

Either they do what Daryll has done, if they think you can do better, and they specify what they believe they are measuring (Daryll said TLT and FWHM), and they do it for at least two meters, preferably those discussed here (Discus and i1pro2) to keep the discussion on topic, or they stop wasting their time (and ours) by posting fragmented information.

Posting just one set of data about one meter (the Discus) without stating what is supposed to be measured, and not measuring the same data with at least another meter doesn't help one bit.

Either we have two sets of spot sizes at a series of distances for at least two meters, or we have nothing.

I have also said that at least for my RS2000, it doesn't seem to matter, I am now using both meters at the same distance without any problem (with full screen patterns), but this is a thread about the Discus, so it might be relevant for other users who have different displays/projectors, and might need for display stability reasons to use smaller patterns or whatever.

Anyway, until a reliable source such as Steve does their homework if they have a problem with Darryl's table and offer an alternative but meaningful and usable set of data that can be field-tested, I'll keep using Darryl's table.

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Last edited by Manni01; 03-26-2020 at 02:03 PM.
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post #102 of 120 Old 03-26-2020, 02:16 PM
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Originally Posted by Manni01 View Post
This is what I've been saying all along.

I'm happy with Darryl's table, but some here are questioning its validity.
I understand that. I was just saying Steve’s number is also in line with Darrell’s, and both being very different from the number quoted for the “spec”.
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post #103 of 120 Old 03-26-2020, 02:28 PM
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Originally Posted by Dominic Chan View Post
I understand that. I was just saying Steve’s number is also in line with Darrell’s, and both being very different from the number quoted for the “spec”.
Yes, and how does that help from a practical point of view, apart from the fact that Steve, unlike others taking issue with Darryl's table, isn't an unknown amateur but a reputable source of information?

Darryl made that table to precisely to get around the inconsistency of the data provided by the various manufacturers: angles, distances, curve, etc.

If the same (competent) person takes a meter, measure its FOV at different distances, and does the same for other meters, then we have a usable set of data, that has some value in the field to match the FOV of two meters.

If someone thinks there is something wrong with Darryl's data, they have to do the same, instead of posting fragmented data or the methodology they suggest to obtain such data.

Anyway, I'm out. Feel free to keep discussing a single set of data with whoever you enjoy spending that time with .

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post #104 of 120 Old 03-26-2020, 02:41 PM
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Have heard back from the Discus manufacturer - they confirm the data I posted.
But also stated that due to the lack of a defined spot edges, the values are 'within tolerances'.
Their suggestion is to use the same 'white bar' approach outlined earlier.

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post #105 of 120 Old 03-26-2020, 02:45 PM
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Originally Posted by Light Illusion View Post
I have requested confirmation from the manufacturer.
Could you ask also to x-rite if they have measured FOV at different distance? Thanks.

Steve, aren't you happy that you are a trusted source even for Manni now?

Anyway, matching small FOV at 1 foot is practically useless, unless you have super crap uniformity panel/PJ, the more you "cover" of the screen/pattern the better. In that case, you really need to match FOV.

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post #106 of 120 Old 03-26-2020, 04:37 PM
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Quote:
Originally Posted by Manni01 View Post
If the same (competent) person takes a meter, measure its FOV at different distances, and does the same for other meters, then we have a usable set of data, that has some value in the field to match the FOV of two meters.
Really, the obsession with FOV's is rather puzzling. The meters aren't sensitive to the area of screen they view. They measure Luminance, which is cd/m^2. So the measurement itself accounts for the area viewed.

So as long as the meter average a largish number of pixels, and as long as your display isn't so non-uniform as to make the measurement un-representative of the overall screen behavior, and as long as stray light and reflections aren't messing with the measurements (contact measurement has advantages here!), the distance from the display is irrelevant.
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post #107 of 120 Old 03-27-2020, 02:29 AM
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Originally Posted by gwgill View Post
Really, the obsession with FOV's is rather puzzling. The meters aren't sensitive to the area of screen they view. They measure Luminance, which is cd/m^2. So the measurement itself accounts for the area viewed.

So as long as the meter average a largish number of pixels, and as long as your display isn't so non-uniform as to make the measurement un-representative of the overall screen behavior, and as long as stray light and reflections aren't messing with the measurements (contact measurement has advantages here!), the distance from the display is irrelevant.
The obsession with matching FOV comes from people who have an agenda in this thread.

I only mentioned a document that is useful if you want to match FOV, saying that it’s been used in the past.

I have said many times that I am not matching FOV anymore and currently use both meters at the same distance, and that with my JVC and my pattern size it seems to be working absolutely fine.

I certainly don’t see a reason to match FOV on a JVC projector if you are using full patterns and are measuring the centre of the screen from 1-2 feet, but the OP was talking about using 10% patterns, so if for some reason he wanted to keep doing that, FOV seems a lot more relevant than with the full patterns he is using now.

For me the main reason I used to think about FOV is that if, for some reason, due to display technology, you have to use small patterns and can’t be close enough to be absolutely sure that you are not measuring some black around the pattern as well, because that’s not desirable.

I know the JVCs well enough, but I don’t have any experience with other technology, so I was erring on the side of caution.

For some reason, some here seem intent on making a mountain out of a molehill, make it sound like FOV has to be scientifically calculated, or is related to uniformity.

Anyway, I’m tired of repeating this, there are lot of knowledgeable people here to help the OP, so hasta la vista, babies!

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post #108 of 120 Old 03-27-2020, 02:58 AM
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Quote:
Originally Posted by gwgill View Post
Really, the obsession with FOV's is rather puzzling. The meters aren't sensitive to the area of screen they view. They measure Luminance, which is cd/m^2. So the measurement itself accounts for the area viewed.

So as long as the meter average a largish number of pixels, and as long as your display isn't so non-uniform as to make the measurement un-representative of the overall screen behavior, and as long as stray light and reflections aren't messing with the measurements (contact measurement has advantages here!), the distance from the display is irrelevant.
The key here is the phrase "as long as your display isn't so non-uniform..."
That is where the goal of FOV matching comes from.
I had assumed that was well understood.

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post #109 of 120 Old 03-27-2020, 05:03 AM - Thread Starter
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Devils advocate; if your display is so non-uniform as to have a big effect on probe matching, what's the point in calibrating it? Your calibration is only valid for the 3 inch circle you matched your probe to. Best junk the display...

I think there is probably more value in matching the angle of incidence that the probe makes to the screen (and the screen to the viewer's gaze) than anything else.
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post #110 of 120 Old 03-27-2020, 05:19 AM
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Quote:
Originally Posted by bobof View Post
Devils advocate; if your display is so non-uniform as to have a big effect on probe matching, what's the point in calibrating it? Your calibration is only valid for the 3 inch circle you matched your probe to. Best junk the display...
I have a feature request for the next generation calibration - support 5DLUT, the additional 2D being the width and height of the display
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post #111 of 120 Old 03-27-2020, 05:40 AM - Thread Starter
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I have a feature request for the next generation calibration - support 5DLUT, the additional 2D being the width and height of the display
It's not as crazy as you think.

My old Sanyo projector (PLV-Z800) had in the service tools; 21x14 x 8 grey levels xRGB channels uniformity correction system to remove colour shading issues on the screen. I used to edit it by hand to tweak uniformity issues that had come in over time. Some of the Epson projectors now actually expose user controls for this, allowing you to set the direction of the shading and adjustment level.

I think JVC do such a good job on their optics that they don't need much if any of this - I've had 4 JVC projectors and they've basically been as close to bang on for uniformity as anyone could ever hope.
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Quote:
Originally Posted by bobof View Post
Some of the Epson projectors now actually expose user controls for this, allowing you to set the direction of the shading and adjustment level.

I think JVC do such a good job on their optics that they don't need much if any of this - I've had 4 JVC projectors and they've basically been as close to bang on for uniformity as anyone could ever hope.
The strange thing is that the Epson projectors do not provide independent R/G/B controls for the 10-point gamma calibration. And they sure aren't bang on.
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OLED results Discus/EODIS/i1pro2

Sorry for not posting any more results from my JVC projector profiling attempts:
Since our living room is my home cinema it's a bit difficult at the moment to find a time
when my girl-friend would be ok with me doing a complete black-out of the room...
Here in Germany we also mostly stay at home at the moment.
But I will bring more results when I've got them.

What I can do is doing measurements with my LG B7 OLED in contact mode.
I do own a Chromapure standard licence.
After some feedback from some of you OLED guys here that I would need to do a volumetric profile with Lightspace (which I don't own) and after getting only complety non-sense results with Calman 5.6.1 (see my post above), I decided to ask Tom Huffman what he thinks about the Discus/OLED/Chromapure combo.
He said it will work.
So I did some test with that.
Here are Greyscale, Gamut and Saturations for my three meters: i1pro2, Discus and a four months old EODIS Rev.B.
Discus and EODIS are both profiled to the same reference measures of the i1pro2.
All measures are done on a 10% window.
One thing though: I was too lazy to complety reset all settings on my TV. So what's been measured is the manually calibrated TV (calibrated with the Discus profiled to i1pro2).

It seems to me, that these results are so close, that there is no reason to doubt the Discus ability to measure an OLED correctly in Chromapure.
What do you think?

Geyscale

i1pro2


Discus


EODIS


Gamut

i1pro2


Discus


EODIS


Saturations

i1pro


Discus


EODIS
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Last edited by TimHamburg; Yesterday at 06:23 AM.
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post #114 of 120 Old Yesterday, 06:08 AM - Thread Starter
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Quote:
Originally Posted by TimHamburg View Post
It seems to me, that these results are so close, that there is no reason to doubt the Discus ability to measure an OLED correctly in Chromapure.
What do you think?
It is hard to tell for sure but it looks like your Discus results show significant hue rotation of the secondaries vs both your i1d3 and i1pro2. This is what you would expect you may see when the meter doesn't track the standard observer particularly well, and the display is not RGB mixing based.
If you look at the saturation sweeps you did, the i1d3 and i1pro2 shapes are basically the same, but your Discus one is notably different (I assume the reason the Discus one looks "better" is because that is what was used to actually calibrate?)
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post #115 of 120 Old Yesterday, 08:32 AM
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Tim, there's more than a reason to doubt the Discus ability to measure a WOLED correctly without a volumetric probe match. Your measurements clearly show that, as @bobof already pointed out.

I suppose you have used the Discus with a matrix created within ChromaPure and not the "general-ld" Discus preset. It would be nice to have the classic 100% WRGB patch reading of Discus (with GENERAL-LD preset and without any other matrix correction) and the i1 Pro 2. I could then show you what happens... Thanks.

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Thanks, guys.
It's still not clear to me, what's going on here.
The Greyscale and Primaries are very close,
only the Secondaries are not.
Does that mean calibrating the Greyscale with the Discus would be fine?
Just problems with secondaries?

To catch up on your experiences:
Is there a thread where this has been discussed before?

For Tom Huffman "the only way to know which is right is to compare with a known reference, which you don't have."
And in earlier email replies to me:
"I have no reason to believe that it (edit:the Discus) would have any trouble reading an LG OLED. They are actually quite easy to read."
"The LG OLEDs are not an RGB source. They are WRGB, which is a totally different animal. They are quite easy to measure. The earliest OLEDs were RGB OLEDs and those are hard to measure."

As for now I can't decide what is right.
I mean the only solution I can see reading your replies is buying Colourspace HTP (or higher) for at least 1125 pounds.
Colourspace HTL will not support the Discus.
So excuse me if I'm not yet willing to give up on my Chromapure license.


@Anger.mikki
Yes, I have used a matrix made with Chromapure.
How do I get the "general-ld" Discus preset.
In Chromapure in the meter setup there is just the "Standard" mode option to be chosen from (or rather choice than that).
Is that "general-id"?
In Calman I tried out all available meter modes, but it gave me identical values through all IREs everytime, so that's not right.
With "the classic 100% WRGB patch reading" do you mean the WRGB matrix reading that Chromapure does anyway?

I'm really thankful to you guys helping me, but I also wanna make up my own mind about things and understand for myself what's going on. I'm just not the believer type...

Last edited by TimHamburg; Today at 01:03 AM.
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post #117 of 120 Old Today, 02:03 AM - Thread Starter
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As far as I can tell the Discus has trouble with any colour measures on WRGB OLED. You can match WRGB for a four colour correction matrix, and those colours will measure fine and give the illusion of a good matrix (the only clue you may have is that some of the luminances for the primaries will be out), but other colours away from the primaries will not. The secondaries are probably the worst case of this as they are each futhest away from the corners of the matrix so the cumulative error is largest, but every colour between the 3 pointed star made by the WRGB measurements will be suspect.

That means that Discus likely can be used for greyscale (at least for SDR), but you need to make sure if you do that that you are performing the matrix with the set already at a correct colour D65 whitepoint for the measured WRGB matrix, as if you have to adjust the white point away from the measured white then the colour error will start to kick in. It might not be a big deal if the adjustment is only small.

If you really want to prove the issue to yourself; use a spectro to calibrate the set so WRGBCMY are all spot on (preferably the whole volume if you have time), prove the calibration is good, and then perform a WRGB matrix correction of the Discus and measure that calibration. Odds are based on the charts you've shown already that you'll see the same pattern - primaries and grey basically OK but with hue rotation on secondaries.

This isn't unexpected as the Discus meter is basically useless with most displays without being matched with a spectro, which already tells you that its filters are a poor match for the standard observer colour matching function; and as the matching is only done with WRGB patches and W does not equal R+G+B the whole premise of matching using FCMM is broken (you will see this if you find the papers on FCMM where this is stated as a requirement for the matching). There have been papers on the subject of trying to find better ways of matching colorimeters for OLED use. In reality what this means is that FCCM matching for WRGB OLEDs only really works for meters that have filters that are already a good match for the standard observer (and so didn't really need much correction anyway!)
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With a correct FCCM (Four Colour Correction Matrix), white is ALWAYS accurate, that's why the grey scale has no problem. Bobof already told you, in the best possible way, how Discus behaves in his latest post. Unfortunately, that was the reason why I sold it (at a bargain)...

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Quote:
Originally Posted by TimHamburg View Post
I mean the only solution I can see reading your replies is buying Colourspace HTP (or higher) for at least 1125 pounds.
Colourspace HTL will not support the Discus.
So excuse me if I'm not yet willing to give up on my Chromapure license.
I believe to get proper volumetric probe matching for the Discus you need more than the software license - you also need a better spectro than the i1Pro2 as its low level readings can't be trusted.

Interestingly, the free LightSpace ZRO supports the Discus.

Last edited by Dominic Chan; Today at 07:08 AM.
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post #120 of 120 Old Today, 07:20 AM
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Quote:
Originally Posted by Dominic Chan View Post
I believe to get proper volumetric probe matching for the Discus you need more than the software license - you also need a better spectro than the i1Pro2 as its low level readings can't be trusted.

Interestingly, the free LightSpace ZRO supports the Discus.
Whie i1 Pro 2 is not a reference spectro and it might be not so good for professionals and some unknown amateur , I have to say that you can have very good volumetric match also with it. A 3x3 cube based profile is quite enough. If you need some test based on Discus/i1 Pro 2 match, just ask to @adolfotregosa

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