Official JVC RS20 / HD750 Calibration and CMS thread - Page 53

Well, it's clear I still have much to improve re my calibration technique! I re-did my grayscale calibration tonight, taking more pains to try to place the I1 colorimeter in a position to get the max ftL. The highest I could get was ~10.5 ftL, which is quite a bit below what I measure at the screen with my CA813 light meter pointed toward the pj and x'ing via the screen gain(~18 ftL). I presume this is because one cannot place the colorimeter ideally to capture all the light coming off the scene. But since the calibration is a relative measure of the colors, hopefully it doesn't matter so much. ???

Anyway, as several of you suggested, I DID get quite different results than with my first attempt: RGB Gains are now (0, -39, -42), compared to (0, -16, -40) on first try.
And the RGB Offsets are now (-2,0,0), compare to the earlier (-5, -4, 0).

The Offsets I now get are actually very close to what Jason had in his initial calibration (-3,0,0), though my Gains have changed considerably from what he got, (0, -23,-75). Is it reasonable to expect that the Offset values would not change so much with lamp aging (mine now has 470 hrs on it), while the Gain values change more considerably?

I iterated back and forth between 100 IRE for the Gain measurements, and 30 IRE for the Offset values, as Curt Palme's guide described, and I'm quite confident that they are correct--at least with my I1 positioned as it was. Positioning the I1 is the last 'variable' that I'm least sure of.

If JVC does do a FW upgrade to make the CMS usable, I can see that the fun will then really begin.

Your offsets sound much more in line now, and yes, the gains do change a lot after a few hundred hours, so that's normal.

Don't know why you get such a difference between the meters, maybe it's due to the HP screen? You should measure about the same.

In any case, if you don't change anything in your setup and measure again tomorrow, you'll see it will probably have drited again.

The i1 is great to do some broad adjustments, which make the most of the difference, but its precision, especially in low light, do not allow for the most accurate greyscale. It's fine for color gamut though, very repeatable, so yes, you'lll have lots of fun when the CMS is fixed...

I don't know if it has been posted here before, but you guys should read the latest issue of Home Theater Magazine in which the HD750 was reviewed and tested; There are some rather extensive discussions on its CMS, color gamut points, THX calibrated-mode, etc, etc, etc...Very interesting reading overall...

The delta between the CA813 and the I1 doesn't matter. The concern is to get the maximum reading out of the I1 by playing with its positioning and orientation. In colorfacts there is a special mode for this it is called Aim Meter. Sadly I haven't seen an equivalent feature in CalMAn.

There is in equivalent feature in Calman (at least since v3.2, I don't know about previous ones). It's the last setup step before launching the calibration module.

Interesting I just find out the tab your are mentioning selecting the CalMan simulated meter. It is not available for the Spyder2. I guess its availability is meter dependant. I will further discuss investigate this.

Looking for some setup advice....

I have a very difficult room to work with, but I fianlly got everything working EXCEPT one thing I am worried about. My ceiling is slanted, and on the end where the projector will be shelf mounted on the back wall...where the back wall meets the ceiling (as high as it can go) the projector will only be about 4 feet off the ground. Not a bad thing except that right in front of the projector is where I have to sit (couch preferably). I am worried that my head will be in the light path. The lens will be above our heads, but just by a little bit. Won't the light path disperse downward quickly to be able to fill the screen and intercept out heads?

The projector will be at the min throw distance (about 10-11 feet) from a 100 inch diagnol screen.

Help...? Thanks.

Use a string, attach it where the lens will be and stretch it to the bottom of the screen. Now sit and see if the string gets in the way.

Thanks Glen. That makes sense. Would the same apply for the horizontal spread as well? From the side of the lens to the side of the screen?

I consider myself a videophile and am ECSTATIC about the prospect of setting up my very own Home Theater room. I have a kuro 9G in the family room, and the prospect of going to a 100 inch screen is making me giddy!!!

I have been learning as much as I can about projectors as this is going to be my once in a lifetime setup (wife's oreders). I want to get the most from my budget. Seems the Epson 750 is a great bang for the buck and a great all around projector. I am really after black levels and shadow detail.

1) Are there better projectors I am missing here at around this price point?

2) My room will be completely light controlled and the projector will be near the lower limit of the throw range (for a 100 inch screen the manual says that about 3 meters is the minimum distance from lens to screen. I will be about 3.5 meters.)............What Stewart screen would you recommend? The Grayhawk RS G3 or the Studiotek 130 G3.

I am thinking that the closeness of the projector may raise the black level, so the gray screen would help lower the black floor...increasing perception of contrast. Plus the image should be plenty bright since the throw distance is so close...I also am a D65 guy so I am not after the unnatural brightness.

But the Studiotek may allow me to dial the brightness down further which could help black level....right? Also if I move to a different house someday I may be using a longer throw distance, so the Studiotek could brighten up the picture due to its higher gain....greater perceived contrast.

I feel pretty lost on the screen subject right now, partly due because I don't know how this projector behaves (how throw distance effects brightness and black level). Any ideas. Thanks

Does the RS20 use the full PC 0-255 range of field when adjusting Gamma or the limited video field which will require the need to adjust black and white levels after making an adjustment to Gamma ?

It was available for my i1 and for the simulated meter, so I didn't even suspect it may not be available for other meters. Sounds strange though, as it's a very basic function. Are you in expert/advanced mode? Also did you install the latest version (3.3)?

This thread long ago became too complex for me to digest, so I hope someone here will humor me. In basic terms: What exactly is "broken" about the JVC's CMS?

Is it that you can't, in fact, dial in accuracy? (Accurate color?)

Or is it that you can perhaps get accurate color but at the expense of something else (e.g. lumens) and a good CMS wouldn't force such compromise?

Or something else?

Thanks.

Hi Rich,

I summarised my view on this here: http://www.avforums.com/forums/dlp-l...ml#post8591471.

CraigR's take on it (his review as he installed an RS-20 combined with a Lumagen Radiance XE) may help as well if you want more details. He posted a link to his review here: http://www.avsforum.com/avs-vb/showt...1#post15820551. You can skip direct to the section "evaluating the JVC-RS20 CMS system" if you're not interested in the whole review.

Hope this helps.

It is really quite simple. The CMS operates in 3 dimensions: saturation, hue, and brightness. The problem with it is two-fold.

First, the controls have an insufficient range of adjustment.

Second, the controls have unwanted interactive effects--adjusting saturation also changes brightness and vice-versa. This makes it almost impossible to get a correct mix of both.

What users have been trying to do in this now very long thread is work around the problem by bringing different controls into the mix--primarily the main Color control (which has its own interactive effects)--to varying degrees of success.

Yes, the Radiance would solve all of these problems because its CMS works quite well. However, be advised that in the THX mode the RS20's color is quite good--assuming you have adjusted the grayscale using the service menu trick--so the substantial cost of the Radiance may not be worth the incremental improvement it would bring. The Radiance is a much better mate for the RS1/2 where the color errors are truly enormous.

Excellent (layman's terms) explanation Tom. (I agree w/ Rich this thread is quite complex)

Question. Since the THX mode color is quite good (w/ adjusted gray scale trick) - does it use a different calibration process to achieve its results?

This is a speculative question, but...


Do you (or others) think the JVC RS30 (or whatever the name will be) will have a fully functioning CMS?

Also, in a few years will it be common for RS20 priced projectors to have really good internal CMS?

So, will the Radiance be good now (for RS20 or RS1/2) and for the next gen of projectors, or will it likely be less useful (not quite obsolete) for the next round of projectors?


Again, I realize these are speculative questions, but hopefully it will generate some thoughts.

Mike

Other than the grayscale fix, there is no calibration process. It is just a relatively accurate preset.

1. No idea.

2. I seriously doubt it.

3. As far its CMS goes, there is nothing about it to become obsolete. Color is color. Its grayscale and gamma tools are also superb and will remain so.

1. Yes, I hope so

2. I think so

3. Marvel is at the door, the world of 4k scaling is here, Radiance has a year or a year and half before to be replaced.

Thanks for the explanation.

As for the THX mode I've only viewed what I believe is the OOTB THX mode. It struck me as generally more accurate, but also didn't seem to give quite the punchy, dimensionality and richness that this projector seems capable of.

Tom and Highlander_AVS -

Thanks for your thoughts.

Hmm, interesting discrepancies between the n=2 respondents so far.
This is speculative, and non-scientific, but I'm looking forward to a tie breaker.

Mike

I'm afraid I disagree with this. The THX mode (as well as the Cinema1 preset) probably use a different process, possibly a fixed LUT table for primaries/secondaries in order to get the accuracy and the linearity it achieves at different levels of stimulus. It's also probably for this reason that gamma is fixed in THX. As the CMS doesn't allow to bring the primaries in without a trade-off in brightness, it has to be a different process... Also it can't really be called a preset as it's not using menu/cms values available to (and modifiable by) the user, like the other presets. It's more like a different mode.

"tweaked" THX is reasonably accurate but incredibly dull and flat compared to a slightly less accurate custom preset (purely from a numbers point of view, as some of the available custom presets are very close to THX visually from a color accuracy point of view) with a custom gamma and a moderate sharpness setting (say around 5). I'm not talking about oversaturated colors (which is subjective, different presets offer different degree of saturation), but 3D, greyscale accuracy and black level. OOTB THX is quite off from a greyscale POV and shouldn't be used in most cases.

I live in Sweden....is the JVC 750 you all are discussing the EU version? If not, I wonder if it suffers from the same constraints as far as calibration?

Also, the THX mode with the Color temp service menu tweak.....is that getting reasonably close to accurate. When some say it is a bit dull, is that meaning it is duller than the standard or just dull for your preferences which may be for an oversaturated picture? I find that a proper calibration provides deep and accurate colors.

For those that are using a higher Gamma than standard I would ask if adjustments to black and white levels to compensate for any changes are required. Thanks.

Do you have any data to support this or this just a subjective assessment?

I would certainly NOT call the grayscale-tweaked THX HD-20 I spent time with as "incredibly dull and flat."

Manni, this is a good example of why people are having a hard time following this thread. You are making a really simple point unnecessarily complex.

THX is a selection one makes from the menu that requires no further manual adjustment. That is the operational definition of a preset. The precise manner in which this preset was engineered is really not relavant to the poster's question, which I understood to focus on whether getting THX required some additional calibration steps (other than the grayscale fix). It doesn't.

The HS20 and HD750 are the same JVC projectors. There are no functional differences that I am aware of between the US and European versions.

I have no idea what the "dull" comment referred to.

Tom, although your first answer was a slight oversimplification, I thought it was a very good summary. However, when asked if THX uses different calibration process, you chose to focus on the word calibration, I chose to focus on the word process. You are right than apart from calibrating the greyscale, there is no further calibration needed to achieve what THX can offer, however it is in my opinion using a different process than the CMS to do so, and this is the way I understood the question.

My apologies if I was wrong, I was not trying to make things over complicated, just to avoid what I felt could be misunderstood/misleading.

After all, this is a calibration thread in AV science forum...

I said dull and flat COMPARED to what custom presets can offer. Some of these presets offer very accurate colors (not oversaturated, as I am aware that this is not everyone's taste), very close to THX visually although they do not measure as close to Rec709 as THX, which is definitely the most accurate mode purely from a measurement point of view.

Bottomline is these presets may not measure as close to rec709, but the picture they offer can be visually acccurate (not oversaturated) and more pleasing (more dimensionality, deeper blacks in a dedicated theater through a custom gamma, more accurate greyscale, and slightly sharper) than THX can offer. It is clear that the greyscale from tweaked THX is still quite off (although not as much as OOTB) and many have posted measurements.

Apart from that, the other elements of what makes a picture better are not measured so I can't give you hard numbers. Which is why, to me, enjoying a PJ doesn't reduce itself to numbers (although numbers do help to achieve a good result when the tool is not broken). After all, I can't give you objective measurements of what makes Nicole Kidman more beautiful than 99% of the women on the planet, it doesn't mean she isn't, and this is only subjective to a point!

I would never describe THX on the RS20 as dull and flat full stop. But compared to what a good custom calibration can offer, it is not, IMHO, the way to get the best experience from this PJ.

Ideally, the CMS will be fixed and it will be possible to be absolutely accurate and offer the best experience.

In the meantime, it forces to a compromise. Some will chose accuracy through THX (which I fully respect), some will chose more control over the picture to get what an accurate gamut alone cannot offer.

No doubt both sides would prefer to have the choice and have access to everything at the same time.