A comparison of 3DLUT solutions for the eeColor box - Page 7 - AVS Forum
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post #181 of 656 Old 02-23-2014, 11:48 AM
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Quote:
Originally Posted by Light Illusion View Post

I don't understand this, but I just took the original LightSpace and Argyll LUTs as supplied by Zoyd, and applied them to a test image.

These are the results.

LightSpace LUT.


And the Argyll LUT

on my PC the argyll pic looks sharper.
more clear edges of the colors.
is this bad?
what am I supposed to see?

Loving D65
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post #182 of 656 Old 02-23-2014, 11:54 AM
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Quote:
Originally Posted by CalWldLif View Post

on my PC the argyll pic looks sharper.
more clear edges of the colors.
is this bad?
what am I supposed to see?

900x900px-LL-745d8c66_Color_Ramps_Horizontal_Vertical.jpeg

Hello, This is how the original picture looks like, without Correction LUT applied.

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post #183 of 656 Old 02-23-2014, 12:22 PM
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then neither are 100% faithful to the original.
red area is missing on the original, blue shape better on the argyll.
green is one side or the other from original.

thanks.

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post #184 of 656 Old 02-23-2014, 12:30 PM
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Originally Posted by CalWldLif View Post

then neither are 100% faithful to the original.
red area is missing on the original, blue shape better on the argyll.
green is one side or the other from original.

thanks.

The picture Steve has used is different at boarder area vs. the one I have posted, it's not exactly the same, look at the peak color edges.

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post #185 of 656 Old 02-23-2014, 12:50 PM
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I'll post this link again to show the problem with the colour gradient image, which has nothing to do with the display or the 3DLUT.
http://www.michaelbach.de/ot/lum-MachBands/index.html

I've noted this perceptual isssue for a while when calibrating, until I found the reason why I stopped looking at gradients when clients were about. It is really hard to destern gradient issues when we have a perceptual problem where by we can generate banding in our heads. Some people will see(interpret) it more, some people less. The real problem is the display chain when it is generating banding and gradient artifacts and believing it is real or not real.

The other issue I have with demonstrating images like this as a result online as posted is that you can't do so without causing more error. My PC display is going to look different to yours, let alone the capturing method and compression artifacts before we even get to perception of what we see.

Image testing is fine, but is limited to the direct display itself, even then some sort of metric reference needs to be used otherwise personal preference will sway perceptual results.

Love it or hate it, the dE and absolute metrics measured via reference equipment is the only way to to remove the human element down to reference despite any limitations of this method.

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post #186 of 656 Old 02-23-2014, 01:11 PM
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Quote:
Originally Posted by CalWldLif View Post

on my PC the argyll pic looks sharper.
more clear edges of the colors.
is this bad?
what am I supposed to see?
Quote:
Originally Posted by <^..^>Smokey Joe View Post

...

The other issue I have with demonstrating images like this as a result online as posted is that you can't do so without causing more error. My PC display is going to look different to yours, let alone the capturing method and compression artifacts before we even get to perception of what we see.

Image testing is fine, but is limited to the direct display itself, even then some sort of metric reference needs to be used otherwise personal preference will sway perceptual results.

Love it or hate it, the dE and absolute metrics measured via reference equipment is the only way to to remove the human element down to reference despite any limitations of this method.

Agree with Smokey Joe.

These images, and the supposed analysis of both, is at best a red herring, and at worst misleading. They should be ignored as such.

Whilst a "corrected version" was subsequently posted of the Argyll LUT, it's still a compressed JPEG that you and I will view on a PC, so is a pointless reproduction of what any LUT will doing to a video signal.

Bear in mind that the original image showed massive banding and clipping - which wouldn't have happened if properly encoded source video was applied to the LUT in the first instance.

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post #187 of 656 Old 02-23-2014, 01:27 PM
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It's curious that despite the best attempt for this thread to be an analytical evaluation and presentation of a fair representation of technologies used by users of this forum, and what I can see as an honest effort to compare apples with apples, it seems to have been subject to the ritualistic shredding of colour science and rational thinking, it's getting boring.

Just remember that it's the pixels your hurting with your harsh words (sad-face emoticon unavailable).

Let's stop comparing apples with fairy dust, and get back to comparing apples with apples.

Peace out!

Cheers
Roland
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post #188 of 656 Old 02-23-2014, 02:01 PM
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Sorry, the images are a direct comparison, so are valid when understanding a LUT generated from the same display, with the same probe, within a close time-scale.

The 'sharpness' in the image colour transitions is not correct, but I do understand that if you have not used the images often it's difficult to know and understand what you are seeing.
The original image i used are also 16bit RGB images, so have no banding, but again that's only possible to assess if you do the same test yourself.

Which you can do, by download the same LUTs and apply them yourself to directly assess the effect they have.
That was the gist of posting them.

But the point was to show that the initial test performed were not comparing apples with apples.
That was later done when the same patch set was used, and the results were very different.

What has happened is that people now understand that different patch sequences can indeed produce very different results - something we were working on already.
That's the most interesting thing from this thread I think.

And if that helps generate better end results for all, that's good.

And the tools that have appeared on Mike's Display Calibration Tools website (www.displaycalibrationtools.com) are a good example of users helping expand the possibilities for themselves.

What's not to like?

smile.gif

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post #189 of 656 Old 02-23-2014, 02:13 PM
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Hi Steve.

The main problem I have with that response is the terminology: "seeing", "assess", "better", "like".

This thread intended to examine, using colour science, objective testing, and well accepted error metrics, the results of various technologies.

Sure, there's a huge merit in talking about all those adjectives I listed above, we all enjoy doing so, but there's ample room elsewhere on this forum for conversations like that.

We've had to endure unscientific arguments and subjective debates with audio over the past thirty years - seems video is going that way quicker that I expected.

Let's keep all that out of the ones which are genuinely trying to be objective and scientific.

Cheers
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post #190 of 656 Old 02-23-2014, 02:23 PM
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Unfortunately, that's a big part of the problem, and part of what I was trying to explain.

There have been may occasions where the accepted mertics show a calibration be be very good, and then when you put up real images the results are appalling - and while not appalling, that is what those images show.
We use such images all the time and can very quickly spot where there are potential failures - it's a big help in defining what works and what doesn't.

As I have said a number of times. we need a different way to technically asses the results of calibration because the level of accuracy we are now striving to attain cannot be proven with the present approaches.
I know that is difficult to do, but it is what we are striving for.

But at the moment, pointing out where issues can and do exist is valid, as hopefully that will enable others to define other ways to make such assessments technically.

Steve

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post #191 of 656 Old 02-23-2014, 02:50 PM
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That's a fair enough endeavour - but where's the new science which show this?

I haven't seen anything yet which suggests a rigorous alternative to current methodologies - just subjective opinion.

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post #192 of 656 Old 02-23-2014, 03:01 PM
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I did post an example of something we have been working on, using 3D cubes to show some potential for volumetric verification.

The concept is valid, but is just experimental at the moment as the cube needs to be interactive, enabling users to interrogate the individual points, as well as quickly see where points are not co-located with their target values for any given colour space. The beauty of this approach is you can very quickly see areas where the calibration deviates from the target colour space in a true volumetric way.

But any verification process will always be limited by the number of points that are actually measures, as you can only accurately verify point you measure - you can't measure a few points and interpolate from there.
This is one of the reasons we use the K10-A as it is both accurate, especially when pre-matched to a spectro, and very fast, enabling a lot of points to be profiled in a short space of time.

It has actually been the evolution of probes that has come the farthest in recent times, enabling far more points to be measured within sensible time-scales.

Hope that helps - we do take accuracy very seriously, and moving to a 21^3 profile set as our standard has made a huge difference in that.

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post #193 of 656 Old 02-23-2014, 03:44 PM - Thread Starter
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Quote:
Originally Posted by Roland.Online View Post


Agree with Smokey Joe.

These images, and the supposed analysis of both, is at best a red herring, and at worst misleading. They should be ignored as such.

Misleading indeed, as I mentioned earlier both LUTs check out identically using those test images on the actual device, however the LS LUT has some light banding in magenta on the color spectrum test pattern. What am I to make of that, did the calibration fail for that LUT? Of course not, the error in reproduction of color on the device using either LUT is far below human perception of color errors in moving images.
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post #194 of 656 Old 02-23-2014, 04:27 PM
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Quote:
Originally Posted by CalWldLif View Post

Quote:
Originally Posted by Light Illusion View Post

I don't understand this, but I just took the original LightSpace and Argyll LUTs as supplied by Zoyd, and applied them to a test image.

These are the results.

LightSpace LUT.


And the Argyll LUT

on my PC the argyll pic looks sharper.
more clear edges of the colors.
is this bad?
what am I supposed to see?
As I've pointed out a number of times now, the two images show BTB and WTW ranges (16..235) being interpreted as a 0..255 range image, and the most obvious difference is that it shows that LS is not preserving the reserved 0 and 255 levels correctly, while the Argyll cLUT is preserving them. Any remaining differences when viewed in an RGB space other than the one the cLUT was created for, are of doubtful significance, because you don't actually know what it should look like. The precision of the mechanism used to apply the cLUTs to this image haven't been revealed either, never mind the awful visual quality of jpegs for this purpose.
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post #195 of 656 Old 02-23-2014, 09:09 PM
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Originally Posted by Light Illusion View Post

Oh and RGB Separation is actually XYZ, which should be obvious to be honest wink.gif
Really ? There's no hint of what it is judging by publicly available information I could find. The graph scales are both unit-less 0..1, which by default one would guess are device values. If the Y scale is related to color measurements, there is no hint as to how the number is derived, or how it relates to visual color errors, ie. delta E's.

In any case, if I understand the general gist of the graph, it aims to give an indication of how additive the display is, something that is quite important when using per channel correction curves, but largely irrelevant when using 3DLuts, for which the very purpose of using them is to be able to correct for non-additivity.
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post #196 of 656 Old 02-24-2014, 02:14 AM - Thread Starter
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Originally Posted by gwgill View Post

Really ? There's no hint of what it is judging by publicly available information I could find. The graph scales are both unit-less 0..1, which by default one would guess are device values. If the Y scale is related to color measurements, there is no hint as to how the number is derived, or how it relates to visual color errors, ie. delta E's.

In any case, if I understand the general gist of the graph, it aims to give an indication of how additive the display is, something that is quite important when using per channel correction curves, but largely irrelevant when using 3DLuts, for which the very purpose of using them is to be able to correct for non-additivity.

That's right, per channel luminance sweeps are used to test additivity. When asked over a year and a half ago what information the user is supposed to derive from these graphs, Tom Huffman also received no answer.
Quote:
Originally Posted by TomHuffman View Post

Can you provide a clear explanation of a test that is used to identify and measure "RGB separation"? What test pattern(s) are used, what are you looking for, and what constitutes passing or failing performance?

A more informative display such as these would help the LS user understand the implications of the deviations from additivity that can be derived from the luminance sweeps. Although luminance sweeps are important they also do not tell the whole story, color difference errors result from both hue and saturation offsets that non-linear devices generate as well, and the luminance separation plots do not tell you anything about those.


pre-LUT


Note that while green has the lowest non-linearity at higher input levels, it actually has the highest color error.

LUT applied


Note that residual scaling errors on the order of a couple of percent are perceptually insignificant.
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post #197 of 656 Old 02-24-2014, 08:43 AM - Thread Starter
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As Graeme pointed out Steve was displaying a video scaled LUT which preserved the sync code (LS doesn't do that) on a full scale device. If you instead do what he should have done and convert the measures to full scale LUTs you get the following. Which is also exactly what I observe on the display.

Argyll LUT

LightSpace LUT
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post #198 of 656 Old 02-24-2014, 11:06 AM
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Quote:
Steve was displaying a video scaled LUT which preserved the sync code (LS doesn't do that) on a full scale device. If you instead do what he should have done and convert the measures to full scale LUTs you get the following. Which is also exactly what I observe on the display.
No, on the second images posted that is not correct - I CORRECTLY scaled the image to fit the LUT, exactly as used within the eeColor box.
However, with the Argyll LUT WTW values are not correctly handled - any image is passed without any attempt at correction.
That is not correct, as many sources have valid WTW content.
We do indeed clip BTB, at user request.

Steve

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post #199 of 656 Old 02-24-2014, 12:19 PM
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So Steve, without intending offence, no one has tackled the issue with this graphic, where is the references?
Or is it solely a judgement of personal preference?

I'm having a hard time getting my head around the reliance on one graphic to make comparisons of complex environments solely by personal judgement.
Personally the graphic needs reference marks to where gradients should be and BTB, WTW or ranges or clipping might occur.


As for the differences in LUT performance, I'd be looking at how the error as dE and absolute is distributed throughout the LUT's. I'd be asking, where is the error?, Is it evenly distributed?, Is it confined to the outer reaches of the LUT?
How do the different methods compare with these sort of questions, and other questions that arrise once the details are discovered?

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post #200 of 656 Old 02-24-2014, 12:36 PM
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Hey, no offence taken at all - I know it can be a very emotive subject, but I'm also very thick skinned...

When I get a chance I'll put up uncompressed versions somewhere, with the issue highlighted.

But, the key here is in getting a new approach with regard to verification metrics - with a focus on volumetric reporting .
With volumetric verification you would be able to quickly see how errors are distributed - which is a good point to raise!

We have our ideas and plans, and I hope others have alternate versions too...
We are getting to critical levels of accuracy now, and what we have seen here is the present approaches we all use just do not cut the mustard.

Steve
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post #201 of 656 Old 02-24-2014, 01:50 PM
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Steve, one thing I find troubling is that you don't seem willing to engage in a dialogue about basic concepts involving color science. Numerous individuals, who have a solid grounding in these ideas, have patiently tried to bring these up (most notably with respect to the idea of measuring performance relative to volumetric space vs. other spaces), and the way you have responded to those arguments suggests that you don't really understand them. Instead, you tend to dogmatically repeat your own beliefs.

Nobody here doubts that you've helped create a successful product, and have valuable experience that can inform you, but there is no shame in admitting ignorance - I don't think there is a single person in the industry who knows it all - and there is nothing wrong with asking for clarification on a concept if it doesn't make sense to you right off the bat.
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Quote:
Originally Posted by zoyd View Post

A more informative display such as these would help the LS user understand the implications of the deviations from additivity that can be derived from the luminance sweeps. Although luminance sweeps are important they also do not tell the whole story, color difference errors result from both hue and saturation offsets that non-linear devices generate as well, and the luminance separation plots do not tell you anything about those.

Zoyd,

the RGB separation graph is ONE out of many things that report on a display's performance in a specific area, same as all the other graphs do. It is obviously not a one single graphs that tells the entire story - no graph can do that.

The graphs and evaluation tools that you recommend are all available today - and they are being used.

- M

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post #203 of 656 Old 02-24-2014, 06:44 PM
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Quote:
Originally Posted by 1forsnow View Post

Steve, help me understand something. As a possible future HCL owner, why would i spend $750 on software and start a guessing game with patch sequences from a newly generated website to possibly give me ideal results? How come your original set of 4913 patches are not ideal anymore(hence the need for different patches or sequences)? Does this mean that all the post-production houses that used your original 4913 patches, the results are not optimum?
And if you have to play with different patches, how is this faster? I keep hearing how much faster LS is, but playing with different patches certainly is not faster and is just a guessing game for the correct patch/sequence. Please don't get me wrong I like how flexible your software is, but at the end of the day its about accuracy and the final result with me. Thank you

Please advise

1forsnow,

there is no "perfect" patch sequence, I have a custom patch set here that I really like (ca. 9,500 pts) - but then again could it be better ? Yes, with even more points.... biggrin.gif My meter is fast enough to handle 10K points rather quickly, yours may not so u may need a different set...

The traditional patch (grid) sequences are doing a great job, but everything evolves. Same as we had 6pt cals in HT just a while ago and now we are doing 65^3 LUT's in HT.... smile.gif

Patch sequences are a crucial part of the profiling process (same as meter accuracy etc) and you will want different tools for different tasks - larger sets for profiling and smaller sets for evaluation....

I have various sets for profiling and different ones for evaluation... all shift the coverage and distribution in different areas (brightness / saturation)... one just does Greyscale, 100 pt with R|G|B patches for RGB separation eval - other sets evaluate the gamut with 180 hues with different brightness and saturation levels... Another one is just focused around skin tones... lots of possibilities and approaches.

Lightspace has allowed custom patch set import for a while now giving users the freedom to do so - the internal, traditional grid sequences have a lot of points - and they perform very well, but there are users who want good performing sets with less points, and that was Zoyd's approach here.

And there are users like me - who want DIFFERENT POINTS (big difference), ergo a shift in the hue/saturation/brightness coverage and distribution.

In addition, you might also want to optimize your set for Plasma or other stuff so there will never be a "once-size-fits-all" patch set.....

The problem was that in the past there were no tools to create patch sets or the apps did not allow import of custom patch sets....

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post #204 of 656 Old 02-24-2014, 07:04 PM
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Quote:
Originally Posted by spacediver View Post

Steve, one thing I find troubling is that you don't seem willing to engage in a dialogue about basic concepts involving color science. Numerous individuals, who have a solid grounding in these ideas, have patiently tried to bring these up (most notably with respect to the idea of measuring performance relative to volumetric space vs. other spaces), and the way you have responded to those arguments suggests that you don't really understand them. Instead, you tend to dogmatically repeat your own beliefs.

Nobody here doubts that you've helped create a successful product, and have valuable experience that can inform you, but there is no shame in admitting ignorance - I don't think there is a single person in the industry who knows it all - and there is nothing wrong with asking for clarification on a concept if it doesn't make sense to you right off the bat.

You might not know that, but you can hire Steve and Light Illusion for training and consultation. Then you can ask him all the questions about basic concepts that you have and don't understand yet and I'm sure he'll be happy to explain these concepts to you in detail.

On a side note, I was quite amused by your rather interesting approach: you claim to be asking for help (about basic concepts) yet in the same paragraph you choose to insult the person (that you are asking for help) of not knowing what he is talking about.

In different parts of the world that would explain the non-response, apparently not in ROB FORD'S TOWN. rolleyes.gif


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post #205 of 656 Old 02-24-2014, 07:22 PM
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Originally Posted by Iron Mike View Post

You might not know that, but you can hire Steve and Light Illusion for training and consultation. Then you can ask him all the questions about basic concepts that you have and don't understand yet and I'm sure he'll be happy to explain these concepts to you in detail.

On a side note, I was quite amused by your rather interesting approach: you claim to be asking for help (about basic concepts) yet in the same paragraph you choose to insult the person (that you are asking for help) of not knowing what he is talking about.

In different parts of the world that would explain the non-response, apparently not in ROB FORD'S TOWN. rolleyes.gif


- M

I think you completely misunderstood my post. I wasn't asking Steve for help.

Anyway, I think Steve can speak for himself in this matter.
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post #206 of 656 Old 02-24-2014, 07:38 PM
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Originally Posted by spacediver View Post

I think you completely misunderstood my post. I wasn't asking Steve for help.

Anyway, I think Steve can speak for himself in this matter.

no I got ya, u're trying to bait a long time color and calibration expert into a conversation about basic concepts that you think he does not understand... (?)

everybody can have their beliefs about what is the best approach... but then there is theoretical understanding... and then there is technical understanding... and then there is - applause please - practical experience (--> REAL WORLD).

make a checkmark on all of that for one Steve Shaw, plus the success of his product, plus all the high-end clients around the world (you know, the peeps that shoot the movies that you watch).... well, he also worked as a colorist himself....

I do agree that nobody knows everything and everybody can be wrong once in while, BUT I'm genuinely interested what basic concepts of color science you can explain to him ?

Please do tell.
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post #207 of 656 Old 02-24-2014, 07:41 PM
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Originally Posted by Iron Mike View Post

no I got ya, u're trying to bait a long time color and calibration expert into a conversation about basic concepts that you think he does not understand... (?)

Quote:
I do agree that nobody knows everything and everybody can be wrong once in while, BUT I'm genuinely interested what basic concepts of color science you can explain to him ?

Please do tell.

I'm not inclined to waste time reiterating the back and forth between Steve and Zoyd/Graeme/Derek, but if you are genuinely interested, feel free to peruse the thread. G'day Mike.
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post #208 of 656 Old 02-24-2014, 07:59 PM
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Originally Posted by spacediver View Post


I'm not inclined to waste time reiterating the back and forth between Steve and Zoyd/Graeme/Derek, but if you are genuinely interested, feel free to peruse the thread. G'day Mike.

I've read the thread, Derek posted once on page 2... he agreed with the approach of using custom patch sets, as we all do.

Btw, not trying to up-talk Steve here, everything I posted is easily verifiable, it's just that if he needs to learn basic concepts then fore sure a lot of us here need to learn even much more, so I am genuinely interested in a quick overview of these concepts !

That is of course as you say basic concepts of color science..... not stuff from a random document found in a google search, that you interpret your own way....

If you ever find the time, please share.

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post #209 of 656 Old 02-24-2014, 08:13 PM
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Originally Posted by Light Illusion View Post


But - we would still prefer to use a cubic verification check, as delta-e really is a limited method when it comes to checking final accuracy.
We would expect the use of a non-regular patch sequence to cause inaccuracies within the volumetric space, which the delta-e checks are not picking up.

I believe this speaks volumes.
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post #210 of 656 Old 02-24-2014, 08:43 PM
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Originally Posted by spacediver View Post

I believe this speaks volumes.

no problem with any of that.... just read carefully....

1) delta E is "limited" - as stated a thousand times - it's the very first thing to check for and then move on to visual validation using dedicated footage. If ur dE raises red flags then u know what part of the gamut to extra carefully visually validate, so dE is def useful... note when he says "final accuracy".... there were more than one case where dE was more than acceptable but the visual, FINAL validation was not....

2) a non-regular patch set, as in a custom patch set that is NOT well optimized and balanced (those are the keywords here) - will cause inaccuracies. Grid sequences have the disadvantage of a "lot of points" but they do cover quite a lot of space and they are proven to be very effective. What I don't like too much about them is (some of) the distribution, but the extra amount of points makes up for it, especially on very large grid sequences.

the lesson is: if in doubt, use a grid sequence as u know what u're gonna get with a 21^3. Using an experimental not-well optimized and unbalanced patch set might just waste your time and produce inferior results... that is why u should always check / validate the custom patch set before u use it ! This is all doable nowadays !

3) dE does not pick up some inaccuracies that visual validation does. and this has often (but not only) to do with the validation patch sets being used for validation as they are (usually) very small and only cover the main areas.... so if ur custom patch set (used for profiling) caused inaccuracies (in the LUT) somewhere but your small validation patch set is not checking there, well then these specific dE checks won't pick up the inaccuracies...

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