Official JVC RS20 / HD750 Calibration and CMS thread (NEW FIRMWARE V1.1) - Page 13 - AVS Forum
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post #361 of 1634 Old 05-04-2009, 01:35 PM
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Originally Posted by Lawguy View Post

I am just trying to understand why those patterns would not be the correct patterns to use to assess whether the gamut is linear. I understand that professional equipment may be better than that that most of us have available but that is kind of beside the point when it comes to the linearity discussion. Not answering kind of makes it seem like magic and that is not what this forum is about.

It is not magic.

Basically your tools are insufficient for the task. You need a great spectro to get great results with these types of products. You also need to examine colorspace in a way that corresponds to real images. Do you watch color bars and gray ramps or do you watch something else? Your test patterns and your objective function need to be weighted so real images look the best possible. Having perfect color bars and gray ramps are not the real goal.
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post #362 of 1634 Old 05-04-2009, 01:44 PM
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Originally Posted by umr View Post

It is not magic.

Basically your tools are insufficient for the task. You need a great spectro to get great results with these types of products. You also need to examine colorspace in a way that corresponds to real images. Do you watch color bars and gray ramps or do you watch something else? Your test patterns and your objective function need to be weighted so real images look the best possible. Having perfect color bars and gray ramps are not the real goal.


Perhaps you misunderstand the kind of patterns that are being used. These patterns track the saturation of each color from 100% saturation down to 25% saturation. If the gamut was not linear, I would expect that these measurements would not be linear. However, they appear to measure linearly. If I am mistaken, please explain why I am wrong.

If I understand your reference to color bars and test patterns as opposed to real images, am I right that you do not subscribe to the view that a calibrator should calibrate to a standard? I am not saying whether this is the right or wrong view, I am just trying to understand what your view is.

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post #363 of 1634 Old 05-04-2009, 02:05 PM
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Originally Posted by Lawguy View Post

Perhaps you misunderstand the kind of patterns that are being used. These patterns track the saturation of each color from 100% saturation down to 25% saturation. If the gamut was not linear, I would expect that these measurements would not be linear. However, they appear to measure linearly. If I am mistaken, please explain why I am wrong.

If I understand your reference to color bars and test patterns as opposed to real images, am I right that you do not subscribe to the view that a calibrator should calibrate to a standard? I am not saying whether this is the right or wrong view, I am just trying to understand what your view is.

My view is that you need the best tools to get the best results. If you are happy then that is good enough. If not I would explore other options.

When you say each color it sounds like you are just looking at RGBYMCW. There are way more colors than those and some are more important than others. From what I have seen when you adjust the CMS the edge of the triangle is moving more than some of the less saturated colors. In the end I am happy with my results. They are better with the new CMS, but I was also able to get good results with the old one.
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post #364 of 1634 Old 05-04-2009, 02:14 PM
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Hi Jeff,

I follow you completely!

What is the sence of tweaking the gamma to the perfect 2.2 if this introduces jumps in the grayscale, you may not forget that the gamma of the LCOS is around 2.1 and every kind of tweaking through the user menus is done through look up tables in the Silicon Optix processor only operating in 10-bit, while the LCOS itself is doing its gamma in 12-bit. So all kind of little tweaks could result in contouring artifacts. So I prefer a little off gamma, but smooth colors/gray rendering without any jumps!

The same is through for the CMS, this CMS is doing so much calculations in a questionable color space (HSL), what are the errors introduced due to rounding? Like I mentioned before on this forum I've seen allready 2 scenes in the movie "Hard Candy" showing severe color contouring artifact I don't see at all in THX mode. Maybe THX is doing their CMS in the RGB space? Maybe that is the reason for the short black screen when switching to THX? So I prefer a little less accurate THX mode next to a perfect CMS calibrated mode having color contouring artifact on some smooth color transitions! And by the way, I measured the THX mode to be very close to Rec.709, even a little oversaturated.

What my point is, getting a "film-like" experience is only possible by avoiding all kinds of digital rounding errors generated by all kinds of tweaks just to get a perfect measurement. You may not forget that our eyes/brain are "specialized" in adaptation, for example if the x,y coordinates are a little off of white, our brains will eliminate this. By the way, how many movies have natural colors these days? So if there is a little error, who will ever know. While on the other hand if there is a contouring artifact, everybody looking for quality will notice it.

Just my opinion...

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post #365 of 1634 Old 05-04-2009, 02:21 PM
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Originally Posted by Ignace View Post

Hi Jeff,

I follow you completely!

What is the sence of tweaking the gamma to the perfect 2.2 if this introduces jumps in the grayscale, you may not forget that the gamma of the LCOS is around 2.1 and every kind of tweaking through the user menus is done through look up tables in the Silicon Optix processor only operating in 10-bit, while the LCOS itself is doing its gamma in 12-bit. So all kind of little tweaks could result in contouring artifacts. So I prefer a little off gamma, but smooth colors/gray rendering without any jumps!

The same is through for the CMS, this CMS is doing so much calculations in a questionable color space (HSL), what are the errors introduced due to rounding? Like I mentioned before on this forum I've seen allready 2 scenes in the movie "Hard Candy" showing severe color contouring artifact I don't see at all in THX mode. Maybe THX is doing their CMS in the RGB space? Maybe that is the reason for the short black screen when switching to THX? So I prefer a little less accurate THX mode next to a perfect CMS calibrated mode having color contouring artifact on some smooth color transitions! And by the way, I measured the THX mode to be very close to Rec.709, even a little oversaturated.

What my point is, getting a "film-like" experience is only possible by avoiding all kinds of digital rounding errors generated by all kinds of tweaks just to get a perfect measurement. You may not forget that our eyes/brain are "specialized" in adaptation, for example if the x,y coordinates are a little off of white, our brains will eliminate this. By the way, how many movies have natural colors these days? So if there is a little error, who will ever know. While on the other hand if there is a contouring artifact, everybody looking for quality will notice it.

Just my opinion...

Ignace.

When you watch THX mode a CMS is at play. Unfortunately, the errors with it are very distastefully undersaturated. Actually, it is very spooky how sensitive we are to good color. I can easily see a 1% plus green error in gray scale on some images. Knowing that raises the bar considerably.

The points you raise are all valid. It is also very difficult to get perfect xyY measurements. Hitting some target values with a tool is not that tough, but the tool can be wrong and you are likely missing something else if you are not careful. In general people sample far too few things with their tools and do not check other issues like the rounding errors which can be horrific.
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post #366 of 1634 Old 05-04-2009, 02:26 PM
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Originally Posted by umr View Post

My view is that you need the best tools to get the best results. If you are happy then that is good enough. If not I would explore other options.

When you say each color it sounds like you are just looking at RGBYMCW. There are way more colors than those and some are more important than others. From what I have seen when you adjust the CMS the edge of the triangle is moving more than some of the less saturated colors. In the end I am happy with my results. They are better with the new CMS, but I was also able to get good results with the old one.

Your tools are certainly better than most of ours. Your customers seem to be very happy with what you do. I am just trying to understand how you figured out that the gamut on the RS20 isn't linear. If you are right, everyone here is calibrating incorrectly. If you are wrong, well, you are wrong(assuming it is proper to calibrate to a standard). I am just trying to figure out who is wrong.

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post #367 of 1634 Old 05-04-2009, 02:29 PM
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Originally Posted by Lawguy View Post

When I measure 25%, 50%, 75% and 100% saturation patterns, things look pretty linear.

Is there something else I should be measuring?

In order to cover the point.

@ Manni
In reply to Steremandan you supplied the saturations at 75% stimuli from your 3rd attempt.
Would you please produce the same graph at 100% stimuli with the same conditions/parameters.

The 75-100% stimuli is the critical area for saturations higher than 80%
That could be the reason why your very first calibration attempt at 100% was not satisfactory. Then you targetted gamut at 75% which could presumably balance residual linearity issues??

Will be away for the rest of the week...
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post #368 of 1634 Old 05-04-2009, 02:41 PM
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Originally Posted by Lawguy View Post

Your tools are certainly better than most of ours. Your customers seem to be very happy with what you do. I am just trying to understand how you figured out that the gamut on the RS20 isn't linear. If you are right, everyone here is calibrating incorrectly. If you are wrong, well, you are wrong(assuming it is proper to calibrate to a standard). I am just trying to figure out who is wrong.

I can tell you mine looks awfully close to my 151FD upstairs and the Sony XBR CRT's I have worked on. It is also closer to the Arclight Cinema in Hollywood that I use as my reference theater than my Pioneer. I am not saying what others are doing in concept is totally wrong. It is just incomplete and their tools are so poor it is leading people off the path. My i1 Pro is as much as 0.01 in xy off on color on these displays which is not close enough. I can come much close eyeballing a display than that.

Looking at their CMS settings on my projector also shows problems with the image not matching my 151FD very well at all. One set of settings made blue pretty purple for example. I find CMS settings between various projector samples has also not changed that much. Gray scale is widely different between units, but not the CMS.
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post #369 of 1634 Old 05-04-2009, 02:49 PM
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Hi,

Can you give me an example in what areas the THX mode is undersaturated, or is it more general for all colors that are having a low percentage of saturation?

Until now I was preferring the THX mode because I didn't see any rounding artifacts in smooth colors transitions, which I find not acceptable.

Do you have tips to avoid rounding artifacts when calibrating the CMS of the RS20? Or is this a secret ;-)? Because until now my results are unacceptable towards roundings.

By the way I'm using a Minolta CS-200.

Ignace.
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post #370 of 1634 Old 05-04-2009, 02:53 PM
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Originally Posted by Ignace View Post

Hi,

Can you give me an example in what areas the THX mode is undersaturated, or is it more general for all colors that are having a low percentage of saturation?

Until now I was preferring the THX mode because I didn't see any rounding artifacts in smooth colors transitions, which I find not acceptable.

Do you have tips to avoid rounding artifacts when calibrating the CMS of the RS20? Or is this a secret ;-)? Because until now my results are unacceptable towards roundings.

By the way I'm using a Minolta CS-200.

Ignace.

Unfortunately a CS-200 is not sufficient for the task.

You can judge rounding artifacts by viewing images with shallow color ramps before and after adjustment. Larger changes also tend to be more of a problem than smaller moves. I agree on the rounding errors. If I had those issues I would dump the product. Mine is as smooth as silk.
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post #371 of 1634 Old 05-04-2009, 03:08 PM
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Sometimes I just have to laugh at the forum. We have all extremes from using the CMS to go outside of any standard to suit personal taste to specialist with expensive tools and almost master of Kung Fu like calibration experience to where even if you had the proper weapons my son your Kung Fu would not be good enough.

Never become so involved with something that it blinds you.
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post #372 of 1634 Old 05-04-2009, 03:08 PM
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Originally Posted by umr View Post

Unfortunately a CS-200 is not sufficient for the task.

You can judge rounding artifacts by viewing images with shallow color ramps before and after adjustment. Larger changes also tend to be more of a problem than smaller moves. I agree on the rounding errors. If I had those issues I would dump the product. Mine is as smooth as silk.

How are you sure you have viewed enough image with shallow color ramps?
Do you have special testpatterns for this?

To be honnest I don't think the measurement equipement will solve this issue. We use the CS-200 for calibrating medical displays, so I doubt it is not good enough for entertainement? Or I you measuring thousands of different colors during a calibration? Or are you anticipating on the kind of calculations the CMS is making for the entered HSB values to minimize rounding errors in shallow color ramps?

A pitty that the green gammut of the PJ is so huge, this is all color resolution of the 30-bit thrown away!

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post #373 of 1634 Old 05-04-2009, 03:14 PM
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Originally Posted by Ignace View Post

How are you sure you have viewed enough image with shallow color ramps?
Do you have special testpatterns for this?

To be honnest I don't think the measurement equipement will solve this issue. We use the CS-200 for calibrating medical displays, so I doubt it is not good enough for entertainement? Or I you measuring thousands of different colors during a calibration? Or are you anticipating on the kind of calculations the CMS is making for the entered HSB values to minimize rounding errors in shallow color ramps?

A pitty that the green gammut of the PJ is so huge, this is all color resolution of the 30-bit thrown away!

Ignace.


The CS-200 does not have the spectral resolution to get colors right on this product. Medical displays are a completely different game. A CS-200 is very similar in capability to my i1 Pro.

I have watched 100's of hours of material on my JVC. The technique I use is working fine.
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post #374 of 1634 Old 05-04-2009, 03:16 PM
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Sometimes I just have to laugh at the forum. We have all extremes from using the CMS to go outside of any standard to suit personal taste to specialist with expensive tools and almost master of Kung Fu like calibration experience to where even if you had the proper weapons my son your Kung Fu would not be good enough.

Kung Fu is surely not my stuff, although I'm an engineer. I only want to have a "film-like" experience when watching movies. Isn't that our main goal?
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post #375 of 1634 Old 05-04-2009, 03:19 PM
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Kung Fu is surely not my stuff, although I'm an engineer. I only want to have a "film-like" experience when watching movies. Isn't that our main goal?

I have the same goal. My theater now has better PQ than the Arclight, but my audio still needs a little work.

I just wish my RS20 looked as good as a Lumis after I am done with those, but that will never happen.
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post #376 of 1634 Old 05-04-2009, 03:20 PM
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The CS-200 does not have the spectral resolution to get colors right on this product. Medical displays are a completely different game. A CS-200 is very similar in capability to my i1 Pro.

I have watched 100's of hours of material on my JVC. The technique I use is working fine.

Damn! He's keeping it secret
Do you want to visit Belgium for a calibration ?
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post #377 of 1634 Old 05-04-2009, 03:25 PM
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Damn! He's keeping it secret
Do you want to visit Belgium for a calibration ?

I used to work in Europe in my engineering days, but I only go there for vacation after I retired. I was in Belgium in 2007 on vacation.

Unfortunately my PR-670 is restricted to the US by Photo Research.
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post #378 of 1634 Old 05-04-2009, 03:33 PM
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Damn! He's keeping it secret....

Even if I told you exactly what I was doing you would never spend the money to do it. It would cost you a bunch of time and money to replicate it. I have custom calibration software that I use with a programmable video generator and a $24,000 spectro integrated with a rig that can measure accurately to 1 IRE on these products. It would only benefit my competitors if I was to divulge exactly what I do.
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post #379 of 1634 Old 05-04-2009, 03:37 PM
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I used to work in Europe in my engineering days, but I only go there for vacation after I retired. I was in Belgium in 2007 on vacation.

Unfortunately my PR-670 is restricted to the US by Photo Research.

Maybe a last question to get back on track of the purpose of the forum . What do personally think of the choice to use HSB a space for the CMS? Would RGB not be better, and more linear?

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post #380 of 1634 Old 05-04-2009, 03:46 PM
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Maybe a last question to get back on track of the purpose of the forum . What do personally think of the choice to use HSB a space for the CMS? Would RGB not be better, and more linear?

Ignace.

I have not spent much time thinking about that. I only worry about things I can control. If I had responsibility for the code in these then I would have an opinion.

Thinking about it though HSB seems more likely to have issues than RGB like that found in Samsung products. It would be easy to get in a spot with HSB that was not logical given a specific set of display capabilities. I have seen similar problems with color management systems based on xy coordinate systems. I personally just deal with the hand I am dealt and make the best out of it I can.
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post #381 of 1634 Old 05-04-2009, 03:48 PM
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Even if I told you exactly what I was doing you would never spend the money to do it. It would cost you a bunch of time and money to replicate it. I have custom calibration software that I use with a programmable video generator and a $24,000 spectro integrated with a rig that can measure accurately to 1 IRE on these products. It would only benefit my competitors if I was to divulge exactly what I do.

I still wonder what this Kung Fu can solve on a limited CMS; 6 HSB points in only 10-bit space (if it is even 10-bit) reducing the gammut so much to the Rec. 709?

Ignace.
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post #382 of 1634 Old 05-04-2009, 03:51 PM
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So you gray marketed it from the U.S.? Sweet!

To the boys. If you have a cheap meter, you can play. It fun. Will it be right? Not a chance but it may not be that wrong. If you are happy with the results and you think you have made it better. That's all that counts. Me and my customers get the best of the calibrators who have the best equipment. I'd rather watch the results then spend my leisure hours trying to do it myself. And I am ISF certified, have calman pro, a radiance, and at one time or another had or have almost all of the cheaper meters discussed here.

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post #383 of 1634 Old 05-04-2009, 03:53 PM
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I still wonder what this Kung Fu can solve on a limited CMS; 6 HSB points in only 10-bit space (if it is even 10-bit) reducing the gammut so much to the Rec. 709?

Ignace.

Who said Rec. 709 is the goal for film? Film is not Rec. 709. The cool thing about these units is that they can restore part of the lost film gamut while not distorting key colors.

We can hit Rec. 709, but that will not restore the look to what we see in a reference theater.
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post #384 of 1634 Old 05-04-2009, 04:01 PM
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So you gray marketed it from the U.S.? Sweet!

To the boys. If you have a cheap meter, you can play. It fun. Will it be right? Not a chance but it may not be that wrong. If you are happy with the results and you think you have made it better. That's all that counts. Me and my customers get the best of the calibrators who have the best equipment. I'd rather watch the results then spend my leisure hours trying to do it myself. And I am ISF certified, have calman pro, a radiance, and at one time or another had or have almost all of the cheaper meters discussed here.

Correct, that is why I am concerned about the color contouring artifacts I have seen in the movie "Hard Candy". Because I've seen if you change the CMS points, it does not seem to affect the issue. Any measurement tool will probably give the same artifact? I can only say I don't see it in THX, and I don't trust completely the user tunable CMS.

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post #385 of 1634 Old 05-04-2009, 04:04 PM
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Correct, that is why I am concerned about the color contouring artifacts I have seen in the movie "Hard Candy". Because I've seen if you change the CMS points, it does not seem to affect the issue. Any measurement tool will probably give the same artifact? I can only say I don't see it in THX, and I don't trust completely the user tunable CMS.

Ignace.

I have not looked at Hard Candy, but a properly tuned CMS will not add artifacts. Poorly set ones definitely do. I saw one case with a Radiance where the Pixar logo was full of purple blocks mixed with the cyan background.

What you would find with better tools are that display gamuts are frequently not as wrong as cheaper instruments indicate. Because of this people are running out of range and creating artifacts.
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post #386 of 1634 Old 05-04-2009, 04:07 PM
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Who said Rec. 709 is the goal for film? Film is not Rec. 709. The cool thing about these units is that they can restore part of the lost film gamut while not distorting key colors.

We can hit Rec. 709, but that will not restore the look to what we see in a reference theater.

Correct, movie is not Rec. 709. But the transfer to for example BluRay is converted to Rec. 709, mapping too saturated colors to less ones. How can you restore afterwards what is lost? It is like trying to de-interlace a video signal, there are always situations where it doesn't work.

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post #387 of 1634 Old 05-04-2009, 04:10 PM
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Correct, movie is not Rec. 709. But the transfer to for example BluRay is converted to Rec. 709, mapping too saturated colors to less ones. How can you restore afterwards what is lost? It is like trying to de-interlace a video signal, there are always situations where it doesn't work.

Ignace.

The key is to do it subtly with the colors that we are most sensitive to that differ from film the most while not not ruining the most important colors. Basically you must reverse the process used to convert the film. JVC has the best shot at this of anything I have seen.
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post #388 of 1634 Old 05-04-2009, 04:16 PM
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I have not looked at Hard Candy, but a properly tuned CMS will not add artifacts. Poorly set ones definitely do. I saw one case with a Radiance where the Pixar logo was full of purple blocks mixed with the cyan background.

What you would find with better tools are that display gamuts are frequently not as wrong as cheaper instruments indicate. Because of this people are running out of range and creating artifacts.

You should get the movie on PAL DVD, and I buy you a Belgium beer if you can get rid of the artifacts on the man's face when he stand on the roof, as well on the cyan churgery clothes of the girl.

Ignace.
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post #389 of 1634 Old 05-04-2009, 05:12 PM
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Originally Posted by Ignace View Post

You should get the movie on PAL DVD, and I buy you a Belgium beer if you can get rid of the artifacts on the man's face when he stand on the roof, as well on the cyan churgery clothes of the girl.

Ignace.

That would be fun.
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post #390 of 1634 Old 05-04-2009, 05:16 PM
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If they shot the girl without any clothes, the problem wouldn't be there and even if it were we wouldn't notice.

Many of the pro people here continually warn about the pitfalls of DIY calibrations. Calibration is part science and part art. Tou have to make small corrections and do them in the right order and at the right points. For example, calibrating at 20 IRE and forcing the point to be right on and be damned what it does to the lower IREs which the cheap meters really have no chance of measuring that accurately. Better to have a small error at say 30 to reduce the errors at lower and then trying for force corrections when the lower measurements are not accurate. Its almost like trying to force a large correction on an audio resonance point with a parametric equalizer. Far better to lower the peak a bit and raise the others a bit. You gotta be smooth and gentle if you want good results. Know the limitations of your measurement device and your correcting system.

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