RS-1, Radiance Primary Gamut Correction - Page 7 - AVS Forum
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post #181 of 839 Old 10-29-2007, 10:33 PM
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There are many reasons to buy a processor other than CMS - but that is best discussed in the video processor forum than here. Off the top of my head aside from calibration controls, you have more inputs of various formats to support more sources with basic calibrations than you would ever want to run wires up the ceiling for. You have support for constant height screens and various source formats to make sure picture always fits your screen. etc. etc. But for the average joe not messing with constant height and has only a few sources - and happy with decoding/deinterlacing on the PJ - does one really need a processor (aside from calibration controls?)
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post #182 of 839 Old 10-29-2007, 10:36 PM
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Quote:
Originally Posted by R Harkness View Post

I'm still hoping someone will answer this post of mine, thanks:

I will set my preference different than Tom. Number one being the grayscale and gamma correction, then the video processing then the CMS. If you could get CMS without grayscale, and went that route, you still would not be correcting the grayscale unevenness. If you have a +Green error in the grayscale, no amount of CMS will correct that. Many people will be extremely happy with the performance of the RS1 with a corrected grayscale and gamma curve alone, provided with the Lumagen HDP/HDQ. Those interested in or insistent on correct colorspace will need the Radiance. In addition to the CMS, the upcoming 21 point grayscale and gamma correction will really make a stunning package.

The additional advantage of the Radiance will allow you to have about the best video processing for all input sources, SD or HD, with separate memories for proper calibration. The Radiance is/will be functional with the HDMI audio, non existant in the earlier Lumagens. Just about gives you the best of everything, as long as it is properly calibrated.

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post #183 of 839 Old 10-29-2007, 10:38 PM
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Quote:
Originally Posted by R Harkness View Post

Problem was I was all set to pull the trigger on the Panasonic 65" plasma. I borrowed my friend's projector to zoom to 65" diag size, to experiment where on the wall I wanted to put the plasma. But when I zoomed the image out and saw The Big Picture....I got hooked on the idea of front projection instead. And, unfortunately, turning a room destined for hanging a plasma on the wall into a full-fledged front projection based home theater is a vastly more complicated project...as so many here know. Now there are SO many things I'm having to juggle it's hard to get even one of them started or completed - wiring done, decor changes, furniture changes/built, lighting done, shopping for drapes, getting the right screen with masking, researching and acquiring the new front-projection-worthy surround system...it's bloody endless and I'm already sick of it and want to just watch movies. Let alone the fact the JVC RS2, which I want, is not even available yet.

Even if you hurry, you probably will not get all done before the RS2 is out........

Glen Carter
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post #184 of 839 Old 10-29-2007, 11:00 PM
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No kidding - go lurk in the HT builder forum for a while - there are some DIY weekenders that have been at it for years! Some even start over in a new house before they finished the one that sold with the old house...
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post #185 of 839 Old 10-30-2007, 08:04 AM - Thread Starter
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Beta build 102207

Last night I had a little time to work with Bob's rig. I redid gamut correction and had primaries and secondaries pretty close but it ended up in the condition where I lost a lot of luminance so I went back to the earlier settings I made when Bob was here. Those settings got the Primaries closer but I think the secondaries were further off as it used some uneven ADD settings in the primaries.

So instead I tried adjusting gamma last night. Bob's rig was saying my gamma was averaging 1.73 and I had the RS-1 on Gamma A.

Using the greyscale control you can adjust gamma but altering the Luma control at the various IRE points. In the default condition each Luma = IRE point... we need to alter that to alter gamma.

I ended up with

IRE = Luma
0 = 0
10 = 8
20 = 13
30 = 20
40 = 29
50 = 37.5
60 = 48.3
70 = 58.9
80 = 70.5
90 = 82.5
100 = 100

This averaged out to gamma 2.35. I had set the target curve to be 2.4 and this fit the curve closely.

As expected by the numbers above comparing gamma corrected vs. not the average picture level seems to drop and the look of the picture changes a bit too. I didn't get a lot of chance to watch anything after completing this though so want to hold off comments about it till I view it some more.

Shawn
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post #186 of 839 Old 10-30-2007, 09:05 AM
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Quote:
Originally Posted by R Harkness View Post

But a CMS obviously isn't the only reason people have been buying processors all these years (since a CMS has never, as far as I know, been offered on a processor). It's those other reasons that I am curious about: aside from the CMS, given the processing chipset of the RS1, what real-world, PQ improvements can be realised in adding the Radiance on to an RS1 or RS2 projector? Surely the CMS isn't the only benefit. I want to know in what other areas, if any, adding a Radiance will allow me to achieve better picture quality vs using the RS1/RS2 without a VP.

As I said, it does offer more powerful grayscale (and gamma) controls, and a future build will offer fairly sophisticated noise reduction. And, of course, you get a central switching station with a lot more inputs than the display alone.

As to your point about processors being around for a long time without a CMS, that's true, but the processing offered in displays used to be worse than it is now. Anymore, I would argue that many, maybe even most, high-end and even mid-range displays have pretty good processing built in. Furthermore, with the proliferation of 1080i (and even 1080p) sources and 1080p displays, the need for high-quality scaling is less than it used to be.

The bottom line is that external processors offer:
  • increased convenience and connectivity
  • SOTA scaling/deinterlacing
  • noise reduction
  • calibration features
What makes the Radiance unusual is its calibration features (CMS, grayscale/gamma controls, and color decoding adjustments), which are unmatched by any other commercially available device. Lumagen also offers the best scaling in the business, but as I said that is less important now than it used to be.

If a targeted display did not clearly benefit from one or more of its calibration features, then it wouldn't be worth 4K to me, but others may differ.

Tom Huffman
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post #187 of 839 Old 10-30-2007, 09:09 AM
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Quote:
Originally Posted by sfogg View Post

Last night I had a little time to work with Bob's rig. I redid gamut correction and had primaries and secondaries pretty close but it ended up in the condition where I lost a lot of luminance so I went back to the earlier settings I made when Bob was here.

Can you say with any precision how much brightness you lose with the CMS fully engaged? How much light do you get from a 100 IRE window with the CMS off as compared to on, assuming that the contrast control is not changed.

Tom Huffman
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post #188 of 839 Old 10-30-2007, 09:10 AM
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Quote:
Originally Posted by R Harkness View Post

Problem was I was all set to pull the trigger on the Panasonic 65" plasma. I borrowed my friend's projector to zoom to 65" diag size, to experiment where on the wall I wanted to put the plasma. But when I zoomed the image out and saw The Big Picture....I got hooked on the idea of front projection instead. And, unfortunately, turning a room destined for hanging a plasma on the wall into a full-fledged front projection based home theater is a vastly more complicated project...as so many here know. Now there are SO many things I'm having to juggle it's hard to get even one of them started or completed - wiring done, decor changes, furniture changes/built, lighting done, shopping for drapes, getting the right screen with masking, researching and acquiring the new front-projection-worthy surround system...it's bloody endless and I'm already sick of it and want to just watch movies. Let alone the fact the JVC RS2, which I want, is not even available yet.

Rich, I can readily relate to your experiences. I did have a 73" dlp rptv that I liked very much, but after going the 'big screen' route of fp I could never go back; it is just so much more engaging, even for simple tv, sports, etc., not to speak of movies. I was lucky to get to my decision point just as the RS1 came out. Sure there will always be something better down the line--and I'll be happy to make such a move in a yr or two--but you have to jump in at some point. I have absolutely no regrets.
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post #189 of 839 Old 10-30-2007, 09:13 AM
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Rich,

Did you notice the comments about the "no-ring scaling" in the lumagen?

There was a post in this thread, with a link to a post that showed a number of scalars and the lumagen.

The image from the lumagen really stood out.

Back when I had my pearl, I tried to check misconvergence with a standard Avia DVD upscaled to 1080 by my Toshiba HDXA1. It looked horrible. SD DVD's played over the Pearl looked really good, but I can only think that they would have looked better if they had been scaled with this "ring-free" scaling, since the test patterns looked so bad. ( I understand that the test patterns could very well have been the worst case scenario, but still)

What would this be useful for? ( others feel free to correct this

1. SD-DVD's, if you happen to have a lot of them.

2. Cable sources.

3. any 720p broadcasts (sports)

Now if you are going to buy the projector and only watch HD-DVD blu-ray and 1080i HDTV, then I guess this would not be that big of a deal.

Additionally, you could put in color corrections for each source, which may not seem like something you would do, but once you get used to seeing colors a certain way, you might be more interested...

Lately, though, we have changed to watching everything down in the theater, and out 56" RPTV in the living room serves mainly to quickly check the weather radar and have the lkids play Guitar Hero in a place that we at least get to see them.

Best Regards,
Doug
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post #190 of 839 Old 10-30-2007, 09:25 AM - Thread Starter
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Tom,

"Can you say with any precision how much brightness you lose with the CMS fully engaged?"

Somewhere around 60% when it occurs. This is not from the CMS itself as you do not see the loss in brightness on the internal patterns which are of course going through the gamut correction too as verified by watching the saturation change without the brightness getting lost... it actually increases slightly.

The build where Lumagen doubled the available range of the control also tries to automatically prevent color clipping and hold greyscale constant when the gamut is adjusted. I assume the brightness loss is related to this somewhere and is likely some sort of a bug.

Shawn
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post #191 of 839 Old 10-30-2007, 09:27 AM - Thread Starter
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"Now if you are going to buy the projector and only watch HD-DVD blu-ray and 1080i HDTV, then I guess this would not be that big of a deal."

Unless you also happened to run CH and leave the lens in place all the time... then you still end up scaling all your sources. This is what I do.

Shawn
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post #192 of 839 Old 10-30-2007, 10:18 AM
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Quote:
Originally Posted by sfogg View Post

Beta build 102207

Last night I had a little time to work with Bob's rig. I redid gamut correction and had primaries and secondaries pretty close but it ended up in the condition where I lost a lot of luminance so I went back to the earlier settings I made when Bob was here. Those settings got the Primaries closer but I think the secondaries were further off as it used some uneven ADD settings in the primaries.

So instead I tried adjusting gamma last night. Bob's rig was saying my gamma was averaging 1.73 and I had the RS-1 on Gamma A.

Using the greyscale control you can adjust gamma but altering the Luma control at the various IRE points. In the default condition each Luma = IRE point... we need to alter that to alter gamma.

I ended up with

IRE = Luma
0 = 0
10 = 8
20 = 13
30 = 20
40 = 29
50 = 37.5
60 = 48.3
70 = 58.9
80 = 70.5
90 = 82.5
100 = 100

This averaged out to gamma 2.35. I had set the target curve to be 2.4 and this fit the curve closely.

As expected by the numbers above comparing gamma corrected vs. not the average picture level seems to drop and the look of the picture changes a bit too. I didn't get a lot of chance to watch anything after completing this though so want to hold off comments about it till I view it some more.

Shawn

Shawn,

I don't think you are going to be pleased with a 2.3 - 2.4 Gamma. It works well with a CRT, but doesn't look pleasing on the digital projectors. I have had my RS1 set to 2.2 and thinking I will try 2.1.

Glen Carter
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post #193 of 839 Old 10-30-2007, 10:38 AM - Thread Starter
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Glen,

I plan on setting up another output configuration with gamma of 2.2 to compare against. Just not enough hours in the day. I set it a little higher based on a few comments that the RS1 might benefit from it.

Shawn
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post #194 of 839 Old 10-30-2007, 11:02 AM
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Quote:
Originally Posted by sfogg View Post

Glen,

I plan on setting up another output configuration with gamma of 2.2 to compare against. Just not enough hours in the day. I set it a little higher based on a few comments that the RS1 might benefit from it.

Shawn

My impression is that the RS1 is way too bright to handle the higher gamma. If your screen is 150" or bigger, it might work, however with my 110" 0 gain screen, 2.4 was terrible, overall picture was too bright and hard to see black detail.

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post #195 of 839 Old 10-30-2007, 11:04 AM
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Quote:
I plan on setting up another output configuration with gamma of 2.2 to compare against. Just not enough hours in the day. I set it a little higher based on a few comments that the RS1 might benefit from it.

2.2 - best overall gamma if you can only have one setting - a compromise between image depth and shadow detail.

2.0 to 2.1 - great for very dark movies where a lot of detail is needed or desired.

2.4 to 2.6 - great for older and/or brighter movies with not much dark content - provides better image depth in mid to bright scenes.

Just my 2 cents worth...
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post #196 of 839 Old 10-30-2007, 11:10 AM
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Quote:
Originally Posted by Bob Sorel View Post

2.2 - best overall gamma if you can only have one setting - a compromise between image depth and shadow detail.

2.0 to 2.1 - great for very dark movies where a lot of detail is needed or desired.

2.4 to 2.6 - great for older and/or brighter movies with not much dark content - provides better image depth in mid to bright scenes.

Just my 2 cents worth...

Bob, I agree and with the Lumagen, we can create a custom curve........ my next project.

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post #197 of 839 Old 10-30-2007, 11:28 AM
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Quote:
Originally Posted by GlenC View Post

My impression is that the RS1 is way too bright to handle the higher gamma. If your screen is 150" or bigger, it might work, however with my 110" 0 gain screen, 2.4 was terrible, overall picture was too bright and hard to see black detail.

Glen,

Perhaps I'm misinterpreting your post but just the opposite is true. Higher gamma# = darker, lower=lighter. It's my theory that a variable gamma on the RS1 would be ideal, 2.1-2.2 in the low end and closer to 2.3 in the top would help offset the lower ansi washout noted with high APL scenes.

With a little luck and patience I'll be able to test my theory.

On a side note do any calibrators here measure gamma using "ansi gamma" type signals? I've felt for sometime that measuring gamma which to into account for the displays ansi contrast would provide a far more accurate curve for real world viewing. I would propose a signal which incorporates a single %grey in the center for measuring but this would be surrounded by many blocks of differing grey intensity with a portion of the available greyscale, the average brightness being the center block for measurement purposes.
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post #198 of 839 Old 10-30-2007, 11:43 AM
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Quote:
Originally Posted by Hughman View Post

Glen,

Perhaps I'm misinterpreting your post but just the opposite is true. Higher gamma# = darker, lower=lighter. It's my theory that a variable gamma on the RS1 would be ideal, 2.1-2.2 in the low end and closer to 2.3 in the top would help offset the lower ansi washout noted with high APL scenes.

With a little luck and patience I'll be able to test my theory.

Higher gamma makes the climb out of black slower then steepens as the IRE level increases. Blacks are too black and as bright as the projector is, it is difficult for the eye to see the black detail. The limitation to distinguish or see high contrast images makes the 2.3 and above gamma curves look poor. These were good for the CRT where fL were usually below 10fL and at times 5fL for white.

I will try some more extreme curves from 1.9 in the low end and 2.4 towards white.

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post #199 of 839 Old 10-30-2007, 11:58 AM - Thread Starter
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Glen,

"My impression is that the RS1 is way too bright to handle the higher gamma."

I run an ND4 on mine.Anyhow, I will see how it looks and as you know it is easy enough to configure numerous gamma curves on the Lumagen's to be able to compare all this.

Shawn
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Quote:
Originally Posted by GlenC View Post

Higher gamma makes the climb out of black slower then steepens as the IRE level increases. Blacks are too black and as bright as the projector is, it is difficult for the eye to see the black detail. The limitation to distinguish or see high contrast images makes the 2.3 and above gamma curves look poor. These were good for the CRT where fL were usually below 10fL and at times 5fL for white.

I will try some more extreme curves from 1.9 in the low end and 2.4 towards white.

Ok I see what you meant now and agree, even at 2.1 this effect of eye biasing is extreme at about 19fL.
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post #201 of 839 Old 10-31-2007, 09:13 AM
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Quote:
Originally Posted by sfogg View Post

"Can you say with any precision how much brightness you lose with the CMS fully engaged?"

Somewhere around 60% when it occurs. This is not from the CMS itself as you do not see the loss in brightness on the internal patterns which are of course going through the gamut correction too as verified by watching the saturation change without the brightness getting lost... it actually increases slightly.

But if you fed an external signal, say a 100 IRE test pattern from a DVD, it would measure 60% dimmer with the CMS engaged than it would with it disengaged?

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post #202 of 839 Old 10-31-2007, 09:56 AM - Thread Starter
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"But if you fed an external signal, say a 100 IRE test pattern from a DVD, it would measure 60% dimmer with the CMS engaged than it would with it disengaged?"

I am working with Jim @ Lumagen about this. How much light you loose depends upon what you measure and how the gamut control is adjusted. The light loss appears to be from their trying to keep the greyscale constant (and avoiding color clipping) when the gamut is adjusted, not from the gamut itself.

The first version of their gamut control did not try to keep greyscale constant and it did not loose luminance like this. Likewise their internal patterns bypass the constant greyscale code and it does not loose light from the gamut control. Kudos to Bob for lending me the Accupel as it is what highlighted this.

I have brought this to Jim's attention and am working with him on it. Jim has said they are still working on the color gamut and are rechecking their constant greyscale code as well as seeing what else may be needed for the gamut control.

Again... this is still beta software (v102207 to be exact) ... it isn't done yet. Jim has confirmed they will keep working on this.

Shawn
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post #203 of 839 Old 10-31-2007, 09:58 AM
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Quote:
Originally Posted by TomHuffman View Post

But if you fed an external signal, say a 100 IRE test pattern from a DVD, it would measure 60% dimmer with the CMS engaged than it would with it disengaged?

Something is wrong here..... If the CMS is working correctly for White there will be 100% RGB, as the signal changes to 100 IRE Green for example, you should have 100%G+X%B+Y%R (possibly a slight reduction of Green). Now it just doesn't seem likely that the luminance output could drop 60% with CMS active.

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post #204 of 839 Old 10-31-2007, 11:12 AM
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Green is by far the brightest of the 3 primaries, so I'm thinking that if you remove a lot of green (i.e., the resulting gamut will have much less green relative to blue and red), which you have to do to get the saturation levels right, then you might lose a lot of brightness. I'm not sure that this is problem with the Lumagen.

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post #205 of 839 Old 10-31-2007, 11:37 AM
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Quote:
Originally Posted by TomHuffman View Post

Green is by far the brightest of the 3 primaries, so I'm thinking that if you remove a lot of green (i.e., the resulting gamut will have much less green relative to blue and red), which you have to do to get the saturation levels right, then you might lose a lot of brightness. I'm not sure that this is problem with the Lumagen.

The Green over-saturation is corrected by adding a combination of Red and Blue to correct the x/y. We are talking about the color of green, not the amount of green.

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post #206 of 839 Old 10-31-2007, 11:42 AM - Thread Starter
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Tom,

"Green is by far the brightest of the 3 primaries, so I'm thinking that if you remove a lot of green (i.e., the resulting gamut will have much less green relative to blue and red), which you have to do to get the saturation levels right, then you might lose a lot of brightness."

You don't remove green to lower saturation. You add red and blue to the green. Luminance goes UP slightly when you lower green saturation with these controls using the internal test patterns or the external patterns with the earlier revision without the constant greyscale.

The brightness loss is from the 'constant greyscale' in the versions that doubled the range of the gamut control. The details of potentially what/why are on the beta forum.

Again... this is a beta... Lumagen is still working on the gamut control.

Shawn
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post #207 of 839 Old 10-31-2007, 12:44 PM
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Originally Posted by sfogg View Post

You don't remove green to lower saturation. You add red and blue to the green. Luminance goes UP slightly when you lower green saturation with these controls using the internal test patterns or the external patterns with the earlier revision without the constant greyscale.

Does this mean that with the first version adjusting the gamut DID change the grayscale?

By "remove green" I merely meant that the available gamut would have less green than before. After all that's what occurs when you desaturate the green primary by adding red and blue to it: you shrink the green end of the gamut.

BTW, referencing the beta forum is only helpful to other Radiance owners who have access to it. Those like me and others who are not yet but want more information about how it works have to rely on you and other owners to describe it to us.

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post #208 of 839 Old 10-31-2007, 01:20 PM - Thread Starter
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Tom,

"Does this mean that with the first version adjusting the gamut DID change the grayscale?"

It should have but I didn't check it. Altering the primaries alone is going to alter greyscale. After all if you just attempt to correct green you do so by adding red and blue which alters the amount of red/blue/green which alters greyscale. The current attempt may alter greyscale too, I haven't tried checking it back to back using gamut correction or not.

"By "remove green" I merely meant that the available gamut would have less green than before. After all that's what occurs when you desaturate the green primary by adding red and blue to it: you shrink the green end of the gamut."

Functionally it is different though. For example adding blue and red introduces the possibility of clipping blue and red. Just 'removing green' doesn't have that possibility. Your post made it sound like the luminence loss was from 'removing green' and that this is just the way it has to be ("I'm not sure that this is problem with the Lumagen.") which is not the case. When you reduce the saturation of green and look at its luminance before/after it actually increases slightly (couple of lux).

"BTW, referencing the beta forum is only helpful to other Radiance owners who have access to it. Those like me and others who are not yet but want more information about how it works have to rely on you and other owners to describe it to us."

Understood, but the beta forum is still basically closed information that I can't cut and paste from. I was just pointing out that the luminance loss isn't from the gamut control itself. You don't loose light there when you look at patterns going through just the gamut control or patterns that passed through the Radiance before the 'constant greyscale' attempt.

You loose the luminence in the attempt at 'constant greyscale.'

This is still beta software. Lumagen is working on it..... that is the important point.

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post #209 of 839 Old 10-31-2007, 05:19 PM
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"By "remove green" I merely meant that the available gamut would have less green than before. After all that's what occurs when you desaturate the green primary by adding red and blue to it: you shrink the green end of the gamut."

Functionally it is different though. For example adding blue and red introduces the possibility of clipping blue and red. Just 'removing green' doesn't have that possibility. Your post made it sound like the luminence loss was from 'removing green' and that this is just the way it has to be ("I'm not sure that this is problem with the Lumagen.") which is not the case. When you reduce the saturation of green and look at its luminance before/after it actually increases slightly (couple of lux).

I'm going to take a guess here and say that I think that what we are seeing is the result of performing CMS functions from outside the display electronics. My assumption is that when saturation is changed from within a digital display, it is a simple matter of remapping the precise mixture of RGB needed to display a certain color, but when saturation is changed externally, then the change is more complex to affect, as the display needs to be "fooled" into displaying the "correct" color. That is, using green for example, the incoming video signal must have green undersaturated (by adding predetermined amounts of red and blue to it) and then the display continues to oversaturate green as it normally does. The undersaturation of the video signal, when combined with the oversaturation of the display, effectively cancel each other out, thus leaving green at its proper saturation.

This is all conjecture on my part, so I could be totally wrong as to what is happening, so we really need a color expert to come in here and shed some light (pun intended) on the situation.
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post #210 of 839 Old 10-31-2007, 05:27 PM - Thread Starter
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"I'm going to take a guess here and say that I think that what we are seeing is the result of performing CMS functions from outside the display electronics. "

It isn't.

It is from their attempt to keep greyscale constant. That is where the loss in luminance is coming from.

One more time.... Lumagen is revisiting this.....

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