Official JVC RS20 / HD750 Calibration and CMS thread (NEW FIRMWARE V1.1) - Page 14 - AVS Forum
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post #391 of 1634 Old 05-04-2009, 06:52 PM
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Originally Posted by umr View Post

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.

So true!

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post #392 of 1634 Old 05-05-2009, 02:56 AM
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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.

This is worth exploring further. I assume its like an audio compressor/expander, if you know the original compression curve you can fairly accurately restore the original dynamic range. As the JVC has a larger color gamut it can support a higher than REC709 color "dynamic" range but we have to reduce it so that it matches the source.

If we knew how the colors were compressed in the color space originally, it should be possible to recover some of the original colors. After all, isn't this why JVC designed this projector with such a wide gamut? As a manufacturer, wouldn't it have made sense to set it up for just the REC709 color space so that 99.9% of users would not have a problem with oversaturation. But they chose to build this projector with an expanded gamut - so there must have been a good reason for it. Maybe the reason is so that professional calibrators like UMR can restore a more film like look to the projector, so that the expanded gamut becomes an advantage for the JVC projector rather than a disadvantage - and the basis of a well kept secret (calibrators secret sauce). If we could recover some of the film color space outside Rec709 that would be a distinct advantage of having the PJ calibrated.

I'm speculating on the above, however a good topic to explore further....

Now I have to go back to my HT to complete my DIY JVC projector calibration, where I have +- 1 dE error on grayscale except for 10% where the error is more like 12 dE too green and very obvious. Not sure how I can tackle that, and I certainly did not have this type of error when I calibrated the bulb after 50 hours (its now 150 hours). I also punched in lovingDVD's settings and possibly because of the 10dE error, the image now looks significantly worse than my original calibration effort.

Can I confirm that you want to set HCFR to ""use gamma reference to compute greyscale dE"?? Also that you want to get your target gamma set before fine tuning the grayscale? I can see some interaction between the 2.
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post #393 of 1634 Old 05-05-2009, 03:23 AM
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Originally Posted by deandob View Post

This is worth exploring further. I assume its like an audio compressor/expander, if you know the original compression curve you can fairly accurately restore the original dynamic range. As the JVC has a larger color gamut it can support a higher than REC709 color "dynamic" range but we have to reduce it so that it matches the source.

If we knew how the colors were compressed in the color space originally, it should be possible to recover some of the original colors. After all, isn't this why JVC designed this projector with such a wide gamut? As a manufacturer, wouldn't it have made sense to set it up for just the REC709 color space so that 99.9% of users would not have a problem with oversaturation. But they chose to build this projector with an expanded gamut - so there must have been a good reason for it. Maybe the reason is so that professional calibrators like UMR can restore a more film like look to the projector, so that the expanded gamut becomes an advantage for the JVC projector rather than a disadvantage - and the basis of a well kept secret (calibrators secret sauce). If we could recover some of the film color space outside Rec709 that would be a distinct advantage of having the PJ calibrated.

I'm speculating on the above, however a good topic to explore further....

Now I have to go back to my HT to complete my DIY JVC projector calibration, where I have +- 1 dE error on grayscale except for 10% where the error is more like 12 dE too green and very obvious. Not sure how I can tackle that, and I certainly did not have this type of error when I calibrated the bulb after 50 hours (its now 150 hours). I also punched in lovingDVD's settings and possibly because of the 10dE error, the image now looks significantly worse than my original calibration effort.

Can I confirm that you want to set HCFR to ""use gamma reference to compute greyscale dE"?? Also that you want to get your target gamma set before fine tuning the grayscale? I can see some interaction between the 2.

Restoring the original gammut is only possible if they have applied a certain non-linear curve (saturation wise) to it, if they just kept everything linear and just limited the gammut we can never reproduce the gammut. On the other hand if they applied a non-linear curve we probably are not able to reconstruct because the CMS of the JVC does work linear according saturation? Or is the last not true? I didn't measure myself yet. Then we need an external "expander" to do the job? No?

Two things that I can come up with for the choice of an extended gammut are:
- Marketing, for impressing the people with highly saturated colors, like all consumer products.
- Restore the movie extended color gammut by means of external converters, since to me it is very difficult to extend the gammut through the built in CMS without screwing up the so important skin tones?

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post #394 of 1634 Old 05-05-2009, 03:29 AM
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When I setup my projector, I'm looking to try to reproduce the look of the original film rather than do a rigid rec 709 calibration. I have an idea of how it should look but I don't have the tools so I'm mostly bumbling in the dark. Based on what UMR has been saying I think his philosophy matches mines but with vastly better tools and skills. Pity he isn't based in the UK.
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post #395 of 1634 Old 05-05-2009, 03:41 AM
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Originally Posted by Ignace View Post

Restoring the original gammut is only possible if they have applied a certain non-linear curve (saturation wise) to it, if they just kept everything linear and just limited the gammut we can never reproduce the gammut. On the other hand if they applied a non-linear curve we probably are not able to reconstruct because the CMS of the JVC does work linear according saturation? Or is the last not true? I didn't measure myself yet. Then we need an external "expander" to do the job? No?

Two things that I can come up with for the choice of an extended gammut are:
- Marketing, for impressing the people with highly saturated colors, like all consumer products.
- Restore the movie extended color gammut by means of external converters, since to me it is very difficult to extend the gammut through the built in CMS without screwing up the so important skin tones?

Ignace.

I could be wrong but I think the biggest difference over rec 709 would be in the hues. Rec 709 hues are based on the limitations of legacy display technology. I see no point in limiting a display like the RS20 in this way.
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post #396 of 1634 Old 05-05-2009, 04:25 AM
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Originally Posted by umr View Post

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.

Okay. I see your approach now. You are not calibrating to REC 709 or any other standard. That is fine by me so long as your clients understand that they are not getting a conventional video calibration. There can be lots of debate about how good of an idea this is. Certainly many people think it is a good idea and we have seen lots of people on these forums creating custom gamuts.

Purists will be horrified but the proof is in the pudding. I am skeptical that you can consistently "recreate" the actual colors that were used in given films but I can see how doing this might create a more pleasing experience overall.

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post #397 of 1634 Old 05-05-2009, 06:19 AM
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Okay. I see your approach now. You are not calibrating to REC 709 or any other standard. That is fine by me so long as your clients understand that they are not getting a conventional video calibration. There can be lots of debate about how good of an idea this is. Certainly many people think it is a good idea and we have seen lots of people on these forums creating custom gamuts.

Purists will be horrified but the proof is in the pudding. I am skeptical that you can consistently "recreate" the actual colors that were used in given films but I can see how doing this might create a more pleasing experience overall.

I give people what they want. If someone wants Rec 709 that is what I give them if possible. If they want what I like I give them that if possible. You also cannot deliver what a display cannot do. I am discussing what I personnely like here and what this product is best at. If I want Rec 709 I watch my 151FD which is upstairs.

I personally am horrified by what I see as calibrated displays in almost all cases. Little regard is given to any colors than RGBCMYW and those are hosed by using poor tools. It also appears that very few know what D65 looks like so they make things horribly wrong.
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post #398 of 1634 Old 05-05-2009, 07:10 AM
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Jeff, really curious about the release of your concerns by them I could be agree with you
Infact, my aims is to achieve 2 banks, one pure REC 709 and the other custom extended gamut to "restore" some colors and get the best film-like experience pushing on the DNA of JVC machines

If you plan to come to Italy, feel free to contact me, wish to try your approach
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post #399 of 1634 Old 05-05-2009, 07:22 AM
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umr
Interesting!
Can you offer calibration for both film gamut and hdtv gamut? Does RS20 have multiple memories that can handle two gamuts?
Is your film gamut white point less bright than hdtv gamut white point?

First came original aspect ratio.
Now displays are soon capable of original color gamut!

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post #400 of 1634 Old 05-05-2009, 07:30 AM
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Originally Posted by umr View Post

I give people what they want. If someone wants Rec 709 that is what I give them if possible. If they want what I like I give them that if possible. You also cannot deliver what a display cannot do. I am discussing what I personnely like here and what this product is best at. If I want Rec 709 I watch my 151FD which is upstairs.

Fair enough.

I agree that the accuracy of many of the meters that people use is an issue. This is probably especially true if they are have been sitting around for a while. I also think that amatuers like me are more likely to make fundamental mistakes in calibrating a display. A good calibrator will have developed good habits and procedures.

Still, color error is measured in dE. A determined hobbyist with a good meter and a good CMS can get very good results even if your better equipment produces a result that measures slightly better. If such a hobbyist and you calibrated to the same standard with different equipment, I bet the results would compare very favorably.

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post #401 of 1634 Old 05-05-2009, 07:31 AM
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Originally Posted by Ohlson View Post

umr
Interesting!
Can you offer calibration for both film gamut and hdtv gamut? Does RS20 have multiple memories that can handle two gamuts?
Is your film gamut white point less bright than hdtv gamut white point?

First came original aspect ratio.
Now displays are soon capable of original color gamut!

The RS20 can handle multiple gamuts.

You can make the light output what you like. I tend to like SMPTE light levels, but you could setup multiple different ones along with the gamut. It is a very flexible product assuming you are not trying to toss up too big an image.

I temporarily crank open my iris when guests are over for football and run a little light in the room.
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post #402 of 1634 Old 05-05-2009, 08:09 AM
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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 would love to have someone like you do a calibration on my projector. You have been recommended by a few people whose opinion I trust. The problem is my fear of shipping damage. There was a high rate of damage on these projectors,considerably more so than normal. The first unit that my dealer examined, had to be returned. As a result, I decided to try myself. I tried contacting a local ISF guy first but he was unable to help me as he only did television sets and did never answered my questions about adjusting the CMS. Rather than try another, I purchased a meter and will see what I can do. If I am not happy with the results, I will sell the i1pro and chalk it up to the fun of the hobby, and try contacting another local guy.

Never become so involved with something that it blinds you.
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post #403 of 1634 Old 05-05-2009, 08:11 AM
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I would love to have someone like you do a calibration on my projector. You have been recommended by a few people whose opinion I trust. The problem is my fear of shipping damage. There was a high rate of damage on these projectors,considerably more so than normal. The first unit that my dealer examined, had to be returned. As a result, I decided to try myself. I tried contacting a local ISF guy first but he was unable to help me as he only did television sets and did never answered my questions about adjusting the CMS. Rather than try another, I purchased a meter and will see what I can do. If I am not happy with the results, I will sell the i1pro and chalk it up to the fun of the hobby, and try contacting another local guy.

I was just in your area last week. I go to New Orleans fairly often.

There is nothing wrong with adjusting your own projector.
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post #404 of 1634 Old 05-05-2009, 08:23 AM
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Oh boy, it is getting really deep in here (not referring to any particular person or post)...I need my boots. Where is Greg to set the record straight when it really needs straightening?
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post #405 of 1634 Old 05-05-2009, 09:21 AM
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Hi, Bob!
I tend to agree with you on this one!! I have ordered a i1PRO/Calman software and signal generator to play around with and just basically enjoy the hobby. Much like building subs/wiring HT's and doing things that the average person would not get involved with because they just don't have the passion that we find around these forums. Anyway, my inferior meter will be here today and I will be updating my firmware and start experimenting.

I have 700 hrs on my calibrated HD750 that was done by Michael Chen(TLV). He is going to come back at the end of May to recalibrate the display with his high end gear. I'll let you know how close I can get to his calibration with my low end equipment.

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post #406 of 1634 Old 05-05-2009, 09:44 AM
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Personally I don't want to spend time biting my nails over whether I'll have the last degree of color accuracy. I'll plug in some of the settings, kindly provided by forum members. And if a good calibrationist ends up in Toronto some time I'll likely get a professional calibration at that point.
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post #407 of 1634 Old 05-05-2009, 10:42 AM
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I've followed this for a while now and wonder...

If you pay for a pro, what happens as your bulb ages, does the calibration change? Is a new one needed with each bulb change to keep the level of quality, or once its done the first time are you set and able to fine tune yourself?

How do you tell if your local AV store-recommended guy is good?

Is there a Dummies Guide to this for a smart guy, good learner (but not a computer geek), that hasn't figured out where all the settings are that you speak of? Where do the colorspace graphs come from? I can't find them in the manual yet. Are they all found in a Video Essentials type DVD, or do they come with calibration software and meter?

I had Jason do mine when I bought and its good, but green seems too high at times. I'm fine, but want to learn more and improve if I can (and can afford it). I can easily afford a good pro, but I just can't see paying big bucks and have it only last a year or so unless adjustments are either cheap or can be done by me.

Thanks,

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post #408 of 1634 Old 05-05-2009, 10:48 AM
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I feel bad that I might have been the original post that created this latest discusion.

Sorry
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post #409 of 1634 Old 05-05-2009, 10:52 AM
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UMR. Are you saying iff you buy the right probes, you can do it yourself very accurately. But you are talking about spending something like $10K or more?

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post #410 of 1634 Old 05-05-2009, 11:06 AM
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Quote:
Originally Posted by umr View Post

The RS20 can handle multiple gamuts.

You can make the light output what you like. I tend to like SMPTE light levels, but you could setup multiple different ones along with the gamut. It is a very flexible product assuming you are not trying to toss up too big an image.

I temporarily crank open my iris when guests are over for football and run a little light in the room.

Good to know. I have yet to update with new firmware.
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post #411 of 1634 Old 05-05-2009, 11:11 AM
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Originally Posted by Jeff Smith View Post

Is there a Dummies Guide to this for a smart guy, good learner (but not a computer geek), that hasn't figured out where all the settings are that you speak of? .

http://www.curtpalme.com/forum/viewtopic.php?t=10457

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post #412 of 1634 Old 05-05-2009, 11:13 AM
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My reference was mainly to the posts regarding the "uncompressing" of the film gamut by expanding the gamut of REC 709. If you don't reverse the algorithm of the original processing which "compressed" the gamut to REC 709 in the first place, then "uncompressing" it is simply impossible. Anything other than an exact reversal of the process will give you randomly inaccurate results. It is MUCH better to simply live with the fact that you are working with a reduced gamut and just reproduce THAT gamut as accurately as possible. It's kinda like saying that by reducing the resolution of 1920X1080 material to 720X480 that you can somehow make the reduced resolution look as good as the original, or close to it. NOT GONNA HAPPEN! Once the resolution is gone, you ain't gonna get it back...pure and simple. And you are not going to restore the original film gamut by expanding the gamut of your calibration either, although it is theoretically possible by using an exact reverse LUT of the original LUT used to reduce the gamut to REC 709. I don't even know if the REC 709 transformation LUT is standardized or if different ones are used on a film by film basis, so reversing it would be extremely difficult at best, and much more probably impossible.

As far as the use of cheap or lesser tools to perform calibrations, Jeff (UMR), you seemed to think that your Eye-One Pro was good enough to charge me $100 per hour for your work with it calibrating my Ruby a few years ago. If it was "good enough" for a *professional* to be using back then, I can't imagine that it would be all that bad an instrument to be using now. Or are you offering to go back to all of your past customers and give them a freebie with your new gear?
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post #413 of 1634 Old 05-05-2009, 11:14 AM
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Thanks, good stuff!

Thanks,

Jeff

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post #414 of 1634 Old 05-05-2009, 11:28 AM
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Originally Posted by Bob Sorel View Post

....As far as the use of cheap or lesser tools to perform calibrations, Jeff (UMR), you seemed to think that your Eye-One Pro was good enough to charge me $100 per hour for your work with it calibrating my Ruby a few years ago. If it was "good enough" for a *professional* to be using back then, I can't imagine that it would be all that bad an instrument to be using now. Or are you offering to go back to all of your past customers and give them a freebie with your new gear?

Bob,

What I am using today did not exist three years ago when I was at your place. The i1 Pro is not horrible for all things, but it does have limitations. If you worked on as many products as I do you would see its issues. I am always looking to do better things and targeting the best that is possible. I would be willing to drop by sometime, but it sounds like you would not be interested in what I would show you.

If you do not agree with a gamut stretch that is fine with me. After seeing many films in high quality theaters I find Rec. 709 to be highly deficient for the task of film reproduction. You may like it which is fine by me. You can watch what you want on your display. I will watch what I want on mine. It really does not matter. If you would measure many products you would find that few really do reproduce Rec. 709. Most are doing some kind of color space manipulation to keep the key colors on target to some degree while enhancing the primaries without getting carried away. If you move the primaries to Rec. 709 on many of these you will make the key colors too desaturated like the THX mode on this product.
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post #415 of 1634 Old 05-05-2009, 11:36 AM
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Originally Posted by Bob Sorel View Post

As far as the use of cheap or lesser tools to perform calibrations, Jeff (UMR), you seemed to think that your Eye-One Pro was good enough to charge me $100 per hour for your work with it calibrating my Ruby a few years ago. If it was "good enough" for a *professional* to be using back then, I can't imagine that it would be all that bad an instrument to be using now.

Most professional calibrators strive to improve their calibration capabilities. I migrated from a CP-5000 to a C-5 and now the Microspec. As displays began changing, I visually noticed issues with my original probes. The main reason I carried a PVM-96 monitor as a backup reference. Many of us could still be using our original gear, but the desire to be able to accurately calibrate numerous display technologies and provide customers with the best possible results generate a need for the newer, expensive equipment.
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My reference was mainly to the posts regarding the "uncompressing" of the film gamut by expanding the gamut of REC 709. If you don't reverse the algorithm of the original processing which "compressed" the gamut to REC 709 in the first place, then "uncompressing" it is simply impossible.

This is one area too many seem to overlook or ignore. Rec 709 should be used for HD mastered sources and Rec 601 for non HD. Rarely does anyone use both.

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post #416 of 1634 Old 05-05-2009, 12:05 PM
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If you would measure many products you would find that few really do reproduce Rec. 709. Most are doing some kind of color space manipulation to keep the key colors on target to some degree while enhancing the primaries without getting carried away. If you move the primaries to Rec. 709 on many of these you will make the key colors too desaturated like the THX mode on this product.

This was my original point. The JVC appears to have a completely linear color space and there appears to be no manipulation going on.

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post #417 of 1634 Old 05-05-2009, 12:57 PM
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What I am using today did not exist three years ago when I was at your place. The i1 Pro is not horrible for all things, but it does have limitations. If you worked on as many products as I do you would see its issues.

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Most professional calibrators strive to improve their calibration capabilities. I migrated from a CP-5000 to a C-5 and now the Microspec.

Guys, my only point here is that if the Eye-One was good enough for professional calibrations a few years ago, then it can't be all that bad of an instrument to be used by us DIY'ers now. I'm not criticizing anyone for purchasing better test gear (just the opposite...I am glad that you did! ). Please don't read any more into my statement than what I said.
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If you do not agree with a gamut stretch that is fine with me. After seeing many films in high quality theaters I find Rec. 709 to be highly deficient for the task of film reproduction. You may like it which is fine by me. You can watch what you want on your display. I will watch what I want on mine. It really does not matter. If you would measure many products you would find that few really do reproduce Rec. 709. Most are doing some kind of color space manipulation to keep the key colors on target to some degree while enhancing the primaries without getting carried away. If you move the primaries to Rec. 709 on many of these you will make the key colors too desaturated like the THX mode on this product.

Jeff, I really am not looking for an argument here. If you like what you have done to manipulate your color space, then that is fine by me.
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post #418 of 1634 Old 05-05-2009, 01:01 PM
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Originally Posted by Bob Sorel View Post

And you are not going to restore the original film gamut by expanding the gamut of your calibration either, although it is theoretically possible by using an exact reverse LUT of the original LUT used to reduce the gamut to REC 709.

The LUT need not be strictly invertible at all. It hardly will be. The best that can happen is that from all the possible inversions all will look ok so you can pick any.
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post #419 of 1634 Old 05-05-2009, 01:19 PM
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Originally Posted by mhafner View Post

The LUT need not be strictly invertible at all. It hardly will be.

True. The deeply saturated colors are truncated to the Rec. 709 gamut, so there isn't a way to invert it and get the truncated colors back. It's conceivable, though, that using an expanded gamut may place the edge colors further out, and these deeply saturated colors may (or may not) be closer to what they were originally. The downside with this though is that if a person is using a linear color space as the RS20 seems to use, then this process can create errors to every color within the gamut.

Despite that caveat, I don't have a problem with people calibrating towards a wider gamut. I'm sure if done well it can look good. I do think though that it will be source dependent and there will always be source content where the tradeoffs used can be more noticeable than the gains.

All in all, I wish we had a wider gamut in the source and if we're in the process of wishing, I wish we had less chroma subsampling that 4:2:0
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post #420 of 1634 Old 05-05-2009, 01:23 PM
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Originally Posted by umr View Post

If you move the primaries to Rec. 709 on many of these you will make the key colors too desaturated like the THX mode on this product.

No idea what you mean by "key" colors. There is no particular color in the Rec. 709, SMPTE-C, EBU, or DCI gamut that is any more "key" than any other, except of course the primaries and white point. All other colors are derived from them.

The only THX color that was desaturated on the unit I worked on was green (x307, y0.583), which is not a large error (8.2 CIELAB) but certainly worth fixing. However, I did not check the less saturated versions of the pri/sec colors, if this is what you mean by the "key" colors.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
Springfield, MO

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