HCFR - Open source projector and display calibration software - Page 130 - AVS Forum
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post #3871 of 4999 Old 07-07-2014, 08:00 AM
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Better explanation could be found on these forums:

Quote:
How are these concepts related?

The xy coordinate of a color establishes its saturation and hue. The Y value establishes its brightness. The correct xy coordinate for all primary and secondary colors is defined by reference points on the triangular CIE chromaticity chart. If the color deviates from the reference point by appearing shifted towards other colors on the chart, then its hue is wrong and needs correcting. If a color is shifted closer to or father from the white point on the chart relative to the reference, then its saturation is wrong and needs correcting [= color slider]. Finally, if the color is too bright or too dim relative to the establish standard (not shown on the chart, but determined mathematically), then its brightness is wrong and needs correcting.[= greyscale curve]
Basic Guide to Color Calibration using a CMS (updated and enhanced)

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post #3872 of 4999 Old 07-07-2014, 08:06 AM
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Quote:
Originally Posted by Holiday121 View Post
And also if I am
Correct your highest dE was 2.7 for blue correct?

Did you adjust color to bring down red and green and blue so you favored red?
I didn't have a CMS on my TV so I couldnt tackle any 100% saturation point directly. Both configurations with extremely low color checker dEs in the end also had the lowest avg dE for primaries and secondaries (table with the 100% saturation colors).

In my case it was more important to lower the avg dE (for 100% saturated colors) than to lower dE for blue 100% saturated. I could do this as well - but without a CMS for the individual colors at 100% saturation, not without impacting the others (Or misonfiguring greyscale ("luminance") to a point where it (the whitepoint line) wasnt at 6500k any more (which is not what you want at especially NOT from 30IRE upwards)).

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post #3873 of 4999 Old 07-07-2014, 08:22 AM
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Ok good read thanks.

Here is my plan of approach then.

I don't have cms in my projector as well so planned on doing a 3dlut if I can actually get to that point correctly first.

So first on my htpc using enhanced on my projector to display 0-255 going to set the black and white levels.

Once set I'm going to adjust my greyscale only using the gain and offsets to obtain hopefully lower then 2-3 dE.

Once obtained will adjust the color and tiny running the primary and secondary colors.

Once achieving a good dE there should I go into my gamma to try to achieve a better rgb dE?

Also before i start I am resetting projector back to factory. Should I take a reading of each picture mode with 6500k color temp and 2.4 gamma preset?

As far as the color temp in trying to achieve a straight line across the 6500k point correct? So switching from all the color presets choose the one that would need the least adjustment?
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post #3874 of 4999 Old 07-07-2014, 08:38 AM
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Actually I get to leave work soon going to go home fire it up and try some measurements
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post #3875 of 4999 Old 07-07-2014, 08:40 AM
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Just read your other posts.

You have to look a bit closer at calibration basics. Read the guide everyone is referencing still when it comes to HCFR:
http://www.curtpalme.com/forum/viewtopic.php?t=10457

You can savely ignore all of the "math stuff" in there, as thats what the dE formulas - or thankfully the bar graphs when doing real time readings of patterns in HCFR are for.

The point is the following.

Steps are: brightness, then contrast, then greyscale, then primaries/secondaries (at 100% saturation), then saturation curves (thats the points at 0,25,50,75 and 100 percent of the primaries and secondaries), then color checker, then tweaking. BUT. Adjusting points at each of these steps in return influences the others, some more, some less - so one "run" never gives you the perfect result. Each step you want to look at the previous ones (once brightness and contrast are out of the way - they tend not to change "because of" greyscale or color calibration).

Next step would be, learn what each of the graphs in HCFR represents. They are almost all (free measurement, and near black, near white can be ignored at first.. ) necessary in interpreting your results.

The triangle shows x and y values (chromaticity) of colors, but not their luminance level (Y). To take luminance into account (which is effected by greyscale) you look at the saturation graphs (and there mostly at the one which tracks dE).

As in CMSes you normally only can effect the 100% saturation points of the triangle individually - you look at them first (after brightness, contrast, greyscale ). You also look at them (and more specifically their average (when I write avg its a certain value Im refering to) when first adjusting the color and hue slider.

But, all of this, then effects the saturation graph (0,25,50,75, ..) as well. So you have to take that into account. And in the end you evaluate against color checker SG (if possible (Teds free calibration disk (forums), or (easier) the internal pattern generator of HCFR).

Also, before starting to calibrate AT ALL - you make sure that the TV (projector) knows the RGB color space it is fed (Limited, Full (on Auto the TV should be "listening")), which can be configured for each input and most source devices (most PCs are providing full (per default, can be changed in most graphics cards settings - so make sure to double check), most video devices limited (those have settings as well, doublecheck)). You establish that with black and white clipping patterns.

If using the pattern generator in HCFR, make sure that you configure it for the right color space (0-255 = full, 16-235 = limited) first.

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post #3876 of 4999 Old 07-07-2014, 08:55 AM
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Ok I am on my way home now. Driving at the moment.

I should have some graphs and questions in around a hour or so.

Thanks for helping. I seem to be learning a little at a time

I have around 6 free hours to play with it today

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post #3877 of 4999 Old 07-07-2014, 09:06 AM
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Also, when you've done that - and still are hitting a wall somewhere - you can post (just do no flood this thread) measurement results you've gotten so far. If possible all those slides I posted before. (You could also post a saved session out of HCFR, but you might get fewer eyballs viewing them, because that means that we on our part have to download the file, then start the program, then, ...)

Because we would need them in reference to each other to identify a specific problem.

Also, linear greyscale is important after all - because it effects all colors (not just the ones you are measuring) in all sectors. Use minor deviations to "tweak" results, but not to coursecorrect for certain color errors you're witnessing.

Also - contrast also can be used to "mask" (lower) certain dE's. Contrast at first might even introduce them (when the TV "runs out" of a certain primary at high contrast levels), but once youve eliminated that possibility (eyes (peak white at differente contrast levels) and meter (does reducing contrast _significantly_ lower dEs of white (=introduce an error at the highest levels))), lowering contrast might give you lower peak deltaE's in certain conditions. Point is - don't try to "cheat" yourself to a bit lower values here. Color Checker SG and User "average out" all those "tricks". That s why they are nice for evaluating.

Use Contrast (and Backlight (LCD TV)) - below the level where it introduces significant color errors, just to adjust for a brightness of white that goes with the room light level (search for cd/m2 room light on google to get recommendations).
-

That about sums up what I've learned "beyond the basics" in practice.

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post #3878 of 4999 Old 07-07-2014, 10:01 AM
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Quote:
Originally Posted by Holiday121 View Post
Question in my 10 point gamma adjustment I have a white as well as rgb what does white do
You use white to adjust gamma, otherwise you would need to adjust all colors to maintain color balance.
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post #3879 of 4999 Old 07-07-2014, 10:06 AM
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So adjusting the white will move the rgb as well then right?
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post #3880 of 4999 Old 07-07-2014, 10:49 AM
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Ok question.

In regards as gamma if white adjusts it.

In hcfr what graph do I follow in order to know which way to raise or lower?

In the new guide it's using chroma pure and it does it in real time measurements
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post #3881 of 4999 Old 07-07-2014, 10:57 AM
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Soooo...you should use CIE76 to assess greyscale but CIE2000 for colour?
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post #3882 of 4999 Old 07-07-2014, 11:13 AM
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Quote:
Originally Posted by Holiday121 View Post
Ok question.

In regards as gamma if white adjusts it.

In hcfr what graph do I follow in order to know which way to raise or lower?

In the new guide it's using chroma pure and it does it in real time measurements
I'd use the gamma graph, but you can just do live measures and adjust white to hit "Y target".
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post #3883 of 4999 Old 07-07-2014, 11:18 AM
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Ok noob question. Is the Y target the same across the board for gamma?

Also what is the value I'm looking for
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post #3884 of 4999 Old 07-07-2014, 11:33 AM
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Quote:
Originally Posted by Geoff D View Post
Soooo...you should use CIE76 to assess greyscale but CIE2000 for colour?
edit: Yes CIE2000 for colors. As for greyscale:

zoyd afaik recommends it (76) for "historical accuracy" and "because it produces more noticeable dEs if "something" is off".

But - this is debatable. For example in my quest for the best configuration I found several greyscale graphs where CIE76 was MUCH more forgiving than CIE2000 (not good).

In the end I used to hone in on configurations that both produced very low CIE76 and CIE2000 results - which in my case was feasible, because I only had 2pt greyscale to work with. I guess the recommendation goes to calibrate for 76, but nevertheless, always check the configuration against CIE2000 as well. Also, with greyscale you have the luxury that you an look at a 0 point (the "ideal" line) as well. And you have the whitepoint line (6500K - hopefully ) to check against also. Minimize the errors across all of those. Then check color checker performance and optimize with that in mind as well.. (whitepoint line should NEVER suffer. Not even from 0-20 IRE - just compared my settings, it is obvious which one looks better).
-

As for gamma - there currently is an ongoing debate as to if power 2.2 or bt1886 should be used as reference (both can be set in HCFR to calibrate against). My vote (picture in critical viewing) goes to 2.2 (also it is the mastering standard set in the standard - although Calman and others are reporting, that studios are switching - that came after some reports that studios were using 2.4 for dark room mastering. Dont do that (imho). Decide between 2.2 and bt1886 - bt1886 already is the compromise that gives the 2.4 folks more sway in the matter).


How to "affect" gamma (if that was a question here), most TVs have gamma sliders nowadays to uniformly move the gamma curve - but it can always be done by using 10pt greyscale and raising or lowering values "in accordance with their neighbors " afaik (never tested in my short calibration venture.. ).
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post #3885 of 4999 Old 07-07-2014, 11:43 AM
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Quote:
Originally Posted by Holiday121 View Post
Ok noob question. Is the Y target the same across the board for gamma?

Also what is the value I'm looking for
Stop doing math. Just look at deltaEs. (And read tutorials.)
You configure gamma (the curve) against a chosen preset (either power 2.2 or bt1886 in my opinion). It is a setting in HCFR.

You will then see the gamma target change in the gamma graph in HCFR.
-

Also - If you are calibrating a beamer (are you?), make absolutely sure to do it in a pitch black environment. If you dont (I tried with my LCD using the i1d3 in projector "mode") you will get all kinds of fun deviations from "light pollution". Or put otherwise, you meter reads something, but calculates against values that arent standardised. 6500K graph (white temperature) should always be a straight line at 6500K, remember? Even small deviations are bad.

The gamma curve (afaik? Not booksmart on this, just figuring it must be this way) of course hasnt always the same Y, it consists of measurements across all different greyscale points. Also Y never is "fixed" because you can easily change it with contrast, or backlight, or the canvas your projecting onto - thats why we use a "relative" formula (deltaE) and not absolute values.

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post #3886 of 4999 Old 07-07-2014, 11:51 AM
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See I confuse myself most of the time..


I am going to adjust the greyscale and post you the graphs my gamma is just all screwed up ill show you in a second.. This is just after me adjust brightness contrast and rgb greyscale with high and low end NOT USING the 10 POINT GAMMA
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post #3887 of 4999 Old 07-07-2014, 12:03 PM
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ok so far this is just me adjust red and blue... I have not adjusted green because in the guides it said not to.. Also this is with me not touching the 10point gamma

I have not ever been able to get the rgb bars in the gamma graph to be anywhere near straight ever
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post #3888 of 4999 Old 07-07-2014, 12:12 PM
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Sorry - i was less clear in one regard. The (imho) only time when a novice should look at the Y target is, when setting "peak white" in accordance with room light.

Can be done LAST in the entire calibration (just make sure that you calibrate somewhere against 100-150 cd/m2 (its only the Y reading for peak white we are looking at)), so the colorimeter has something to read.

White is the brightest color, so we look at it (Y) to solve the "how bright is too bright for this room" question.

edit: And this is where I was MOST wrong. In Holiday121's case it turns out his gamma curve being lopsided is the result of most Y targets (for all 10 step greyscale values) being _very_ off. crakarjax pointed out that Y targets get calculated in HCFR once you measure 100% white in greyscale. To reach ballpark Y target figures (= adjust gamma (R,G,B avg)) you normally adjust R,G and B _uniformly_ (in equal amounts) for each specific greyscale value - and thats also what the "white" slider was for (R+G+B), Holiday121 mentioned he sees in greyscale config.

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post #3889 of 4999 Old 07-07-2014, 12:23 PM
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Ok, see your problem with gamma.

You will have to wait until someone more knowledgeable than me can give input on this.
You are calibrating a beamer?

The problem here is, that your gamma is exactly the opposite orientation for the bt1886 reference. And not even parallel to the orientation lines you see which would be power 2.2 (or 2.3 or 2.4, ...).

A gamma slider normaly doesnt change the orientation of the curve (its more of an up/down) - and the only other way I know that gamma can be affected (never done it myself) is 10pt greyscale.

BUT. Gamma in your case very well could also be a factory limitation of the device. So it is possible that you ought to "work with what you have".
-

To get to help you with that we need to know what you are calibrating (if a beamer do you calibrate in a pitch black room). And then you need someone that can tell you "what to do with such a gamma curve". So far I've calibrated three LCDs and one plasma, never saw anything like this - I'm afraid.

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post #3890 of 4999 Old 07-07-2014, 12:28 PM
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Ya I am calibrating a Beamer a JVC r46 projector in a batcave.

No matter what I do I can't get that curve straight. I can get my rgb down real low editing gamma 10 point and everything like that. It's just this gamma curve messing me up.

I was supposed to create a 3dlut which was supposed to correct it but when I did that it still failed
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post #3891 of 4999 Old 07-07-2014, 12:30 PM
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Basically the contrast and brightness are at preference for -1 to -1. 0 both for contrast and brightness are basically dead on

This is the stand still I have been at . Its the gamma .
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post #3892 of 4999 Old 07-07-2014, 12:46 PM
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You need someone to pitch in who has calibrated beamers. My best guess is - that as gamma is "the subtle nuance of "shade" that ads information about the "volume" (narrow/deep) of things in an image" and people cant even seem to decide if they want 2.2 or 2.4, its a bit "too subtle" for your beamer setup? Its a wild guess - idk if Im even in the ballpark.

edit: wrong, see below.

Gamma nevertheless affects color performance (and greyscale), so you should definitely have yours "looked at". *punohthePUN*

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post #3893 of 4999 Old 07-07-2014, 12:51 PM
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I'm just at a complete loss now. Even when I take a reading with just presets that gamma graph is not anywhere even close to being straight
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post #3894 of 4999 Old 07-07-2014, 01:07 PM
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@Holiday121 : Oh come on... The Curt Palme tutorial I linked you to has an entire section dedicated to your very case. http://www.curtpalme.com/forum/viewtopic.php?t=10457

Gamma boost is the keyword you are looking at. Also, according to Palme - this seems to be possible with Lumagen.

So lets conclude - wrong thread to ask how to get your beamers gamma fixed? Didnt even read the basics? *hrm*
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post #3895 of 4999 Old 07-07-2014, 01:21 PM
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Sorry - probably wrong here - gamma boosts only seem to be needed when avg gamma is way to high or low - yours isnt. (Or differently put - yours is both... )

Also according to Palme - lower gamma means "brighter" (hard to use in this context. ) - so according to your graph your blacks are too dark, but your whites are too bright? From a gamma perspective. But Your greyscale tracking is right?

You need someone with more knowledge on beamers....

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post #3896 of 4999 Old 07-07-2014, 01:25 PM
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Ya I don't have a lumagen though. Creating a 3dlut is like it with a htpc and supposed to correct it.

Making some progress adjusting my white in my gama 10 point is straightening my lines out
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post #3897 of 4999 Old 07-07-2014, 01:28 PM
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Ya I have read both the new and old
For those guides . I am missing something somewhere I think in my adjustment and I might of found it with this white point
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post #3898 of 4999 Old 07-07-2014, 01:33 PM
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Ah 10 point greyscale to the rescue. Because your gamma is both too dark and too bright , but your average is right - this might actually be the way.
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post #3899 of 4999 Old 07-07-2014, 01:37 PM
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Well, I've been using HCFR with my ColorMunki for about the last year or so, attached is the latest set of results for my Sony KD55X9005A with the latest HCFR version 3.1.5. I know the saturations are a lil' bit squirly but they're within tolerance, and as for the RGB levels doing the splits at 10%, I've never been able to correct that no matter what I do. I don't think I've done too badly with Sony's limited 2 point control.

Crap, the pic has come out too small. Ermm...

Right, how about this:


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post #3900 of 4999 Old 07-07-2014, 01:40 PM
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So, just ignore everything you've been told about gamma for a second.

When you do a grayscale profile the 100% white Y level is recorded. This 100% luminance sets the Y target value for each of the 10% increments such that if you hit those values, your gamma curve will match the target gamma curve. To effect gamma, increase all of RGB (or just white) or lower them at each level. Hit your Y targets at each level and then redo the grayscale profile to check your new gamma curve.

A bit more info on Y -- notice that the Y target increases from 10% to 90%. This translates simply into increasing brightness, which makes a lot of sense when you think about it.
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