Official JVC RS20 / HD750 Calibration and CMS thread (NEW FIRMWARE V1.1) - Page 20 - AVS Forum
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post #571 of 1634 Old 05-11-2009, 10:28 AM
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Originally Posted by TomHuffman View Post

This is what I once assumed as well, but because of gamma actually it is a little different. Using % values it is approximately R100%, G46%, B46%.

The point is, CMS adjustments need to be made with equal primaries, only "Y" should change. As mentioned before, if you have changes in gamut whit changes in "Y" (i.e. 100%, 75%, 50%....) you need to set the CMS for best overall performance. If the "saturation" of a primary changes due to different stimulus levels (color space triangle changes), all derived colors that use that primary will be different when compared to the target (SMPTE-C, REC 709, REC 601.....).
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Originally Posted by TomHuffman View Post

There can be and you allude to it later in your post. If the colorspace is not linear in that different levels of saturation do not fall where they should on the CIE chart, then compromises need to be made. Stereomandan has done some good work in this regard. It's not a problem with the RS20, but my Sharp 20K is very non-linear in this regard. When I get a fully saturated red correctly calibrated then all of the less saturated reds are significantly off from where they should be in the color space. Thus, I get better measured performance throughout the color space by allowing a little oversaturation at its edge.

As mentioned before, if you have changes in gamut with changes in "Y" (i.e. 100%, 75%, 50%....) you need to set the CMS for best overall performance. If the "saturation" of a primary changes due to different stimulus levels (color space triangle changes), all derived colors that use that primary will be different when compared to the target (SMPTE-C, REC 709, REC 601.....). If the Colorspace starts to collapse (shrink) as "Y" decreases, be careful that it is not a limitation of your instrument.
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Originally Posted by TomHuffman View Post

Any color involves Y. It is part of how a color is defined. What I meant was that for the purpose of checking saturations, it doesn't matter how bright the red is. All that matters is where it falls on the CIE chart.

I agree, Primary and Secondary x/y measurements should be the same at all values of "Y" from 0% to 100%.
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Originally Posted by TomHuffman View Post

The disc-based test patterns out there use constant brightness for the range of saturations, even though, all else being equal, if you simply reduce red's saturation and move it towards the white point, e.g., R100%, G46%, B46% it becomes brighter. Keeping constant brightness is a harmless methodological choice.

This statement makes no sense to me. Your example "if you simply reduce red's saturation and move it towards the white point, e.g., R100%, G46%, B46% it becomes brighter" is exactly the same as saying White is brighter than Red. In R100%, G46%, B46%, Red never changes it's brightness, it is 100%, you have created a new color by adding Blue and Green. Just the same as R100%, G100%, B100% = White.

I don't use DVDs for calibration measurements, with my signal generator, I can measure Primaries and Secondaries in 1% steps if needed. My calibration software provides me with a "auto gamma" where I generally measure RGBCMYW in 10% steps. This is one function that verified a problem with a Sony Qualia optical block.... The blue chip was having a problem, it wouldn't completely shut off. As the gamma test revealed a colorspace that didn't change the blue point, but as the "Y" values dropped, the RGCYM points all started moving, significantly, towards the blue point, extremely collapsing the colorspace.

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post #572 of 1634 Old 05-11-2009, 11:03 AM
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Quote:
Originally Posted by GlenC View Post

The point is, CMS adjustments need to be made with equal primaries, only "Y" should change. As mentioned before, if you have changes in gamut whit changes in "Y" (i.e. 100%, 75%, 50%....) you need to set the CMS for best overall performance. If the "saturation" of a primary changes due to different stimulus levels (color space triangle changes), all derived colors that use that primary will be different when compared to the target (SMPTE-C, REC 709, REC 601.....).

Glen: You are really not understanding me. This has NOTHING to do with testing whether the color tracks consistently at different levels of stimulus. That is a valid test to make, but it is not the one I am talking about. When you say "CMS adjustments need to be made with equal primaries" that is generally how we have always done it. What I am talking about is an enhancement to that, which tests not just the outside edge of the color space, but additional levels of saturation as well. Red should be correct not just at the outside of the color space but throughout as well. Here's an enhanced version of the Rec. 709 color space.



What if a color tracks fine at the outside edge of the color space (what we generally measure) but poorly inside the color space, as in this example?



These are actual measurements from my Sharp 20K. In such cases, it is probably advisable to calibrate to a 50% saturation target using a 50% saturation test pattern (at least for red and blue), as this will give more accurate color throughout the color space, though it will be somewhat oversaturated at its edge.

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Originally Posted by GlenC View Post

This statement makes no sense to me. Your example "if you simply reduce red's saturation and move it towards the white point, e.g., R100%, G46%, B46% it becomes brighter" is exactly the same as saying White is brighter than Red. In R100%, G46%, B46%, Red never changes it's brightness, it is 100%, you have created a new color by adding Blue and Green. Just the same as R100%, G100%, B100% = White.

Not sure what it is you don't understand. As you desaturate red by adding equal amounts of green and blue to it, you move red towards the white point, which makes it brighter. It is as simple as that. The "new" color as you put is what I referring to--red at 50% saturation. It is still red because the dominant wavelength hasn't changed.

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post #573 of 1634 Old 05-11-2009, 01:14 PM
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Quote:
Originally Posted by TomHuffman View Post

Glen: You are really not understanding me. This has NOTHING to do with testing whether the color tracks consistently at different levels of stimulus. That is a valid test to make, but it is not the one I am talking about. ......
Not sure what it is you don't understand. As you desaturate red by adding equal amounts of green and blue to it, you move red towards the white point, which makes it brighter. It is as simple as that. The "new" color as you put is what I referring to--red at 50% saturation. It is still red because the dominant wavelength hasn't changed.

Tom, IF you have the Primaries correctly at their respective targets, the colors generated within the triangle will be correct. You don't "desaturate Red" to create another color. You desaturate Red by adding Blue and/or Green to achieve a primary target. All colors within the "triangle" are derived from the combination of RGB primaries. This is the result of additive colors, not desaturation. If you are not able to achieve a specific color within that triangle, then there is an issue with one or more of the Primary gamma tracking. In your example of a point half way between Red and White, if Green gamma falls short, your point will move off the line towards Magenta. Primary saturation is specifically limited to the outer boundaries. You cannot get a (in your terms) "50% desaturated Red" with a red only signal.

I have no idea what reference signal you are using to determine the various colors in your Sharp.

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post #574 of 1634 Old 05-11-2009, 02:08 PM
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Quote:
Originally Posted by GlenC View Post

Tom, IF you have the Primaries correctly at their respective targets, the colors generated within the triangle will be correct. You don't "desaturate Red" to create another color. You desaturate Red by adding Blue and/or Green to achieve a primary target. All colors within the "triangle" are derived from the combination of RGB primaries. This is the result of additive colors, not desaturation. If you are not able to achieve a specific color within that triangle, then there is an issue with one or more of the Primary gamma tracking. In your example of a point half way between Red and White, if Green gamma falls short, your point will move off the line towards Magenta. Primary saturation is specifically limited to the outer boundaries. You cannot get a (in your terms) "50% desaturated Red" with a red only signal.

I have no idea what reference signal you are using to determine the various colors in your Sharp.

Of course we can't get a "desaturated Red" with a red only signal.
The saturation test colors are at constant brightness; they are all made of R+G+B, two of them having the same level. For example the Red at 50% is made of 203/92/92. (compared to 255)

The purpose of the test is to generate desaturated primaries equally spaced along the lines drawn from the primaries to D65.
This is a very usefull test which can identifiy non-linearity problems, if the dots are not equally spaced, or curved, or if "Y" is not constant.
In one test you have like a 3D picture.

In other words we check different reduced gamuts at 75, 50 and 25% saturation.
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post #575 of 1634 Old 05-11-2009, 02:09 PM
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I think Tom is referring to the fact that the CMS in the Sharp did not work like it should. If the colors at 100% saturation were correct, the colors inside the triangle were not. With the JVC, they have now fixed the CMS to allow for colors to be correct at every saturation level within the triangle.

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post #576 of 1634 Old 05-11-2009, 02:22 PM
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Quote:
Originally Posted by leDahu View Post

Of course we can't get a "desaturated Red" with a red only signal.
The saturation test colors are at constant brightness; they are all made of R+G+B, two of them having the same level. For example the Red at 50% is made of 203/92/92. (compared to 255)

The purpose of the test is to generate desaturated primaries equally spaced along the lines drawn from the primaries to D65.
This is a very usefull test which can identifiy non-linearity problems, if the dots are not equally spaced, or curved, or if "Y" is not constant.
In one test you have like a 3D picture.

In other words we check different reduced gamuts at 75, 50 and 25% saturation.

You run into problems doing this because 0-255 is a PC format while what is being used in video is 16-235. White for digital video is 235/235/235...... If you are using a computer to generate color signals in the 0-255 realm, then they will be off for video display. As soon as you generate a color, 203/92/92, you factor in the PC gamma and the individual gamma of RGB in the projector because nothing is at a reference level. If you measure the Gamma tracking of RGBW for x/y/Y, you can predict the coloration errors you will see as you move in towards white.

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post #577 of 1634 Old 05-11-2009, 02:53 PM
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Here is an example of colorspace gamma errors from a failing Qualia 006 (wide colorspace)
LL

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post #578 of 1634 Old 05-11-2009, 03:11 PM
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Quote:
Originally Posted by GlenC View Post

Tom, IF you have the Primaries correctly at their respective targets, the colors generated within the triangle will be correct.

I just published a CIE chart plotting actual measurements that shows that you can have a correct color at the 100% saturation point for red (0.640, 0.330) and yet it will be incorrect for 50% saturation (0.476, 0.329).

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I have no idea what reference signal you are using to determine the various colors in your Sharp.

I already provided those values. On the Accupel you punch in R100%, G46%, B46%. That gives 50% red saturation. If you want 50% red saturation at constant brightness then you punch in R80%, G36%, B36%. If the display measures 0.476, 0.329, then fine. If it doesn't, then you have a problem with the linearity of the colorspace.

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post #579 of 1634 Old 05-11-2009, 03:13 PM
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Originally Posted by Lawguy View Post

Thanks Tom for sharing what you know about this. I feel I have come a long way in appreciating accurate color and it is in many ways thanks to you being such a persistent advocate.

It's nice to know that my constant harping on this has had some effect other than just annoying people.

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post #580 of 1634 Old 05-11-2009, 03:33 PM
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Quote:
Originally Posted by TomHuffman View Post

I just published a CIE chart plotting actual measurements that shows that you can have a correct color at the 100% saturation point for red (0.640, 0.330) and yet it will be incorrect for 50% saturation (0.476, 0.329).

I already provided those values. On the Accupel you punch in R100%, G46%, B46%. That gives 50% red saturation. If you want 50% red saturation at constant brightness then you punch in R80%, G36%, B36%. If the display measures 0.476, 0.329, then fine. If it doesn't, then you have a problem with the linearity of the colorspace.

Questions:
  1. Does Red change x/y when you go from 100% to 80%?
  2. Is the x/y of Green and Blue the same at 100% and 46%?
  3. Is the "Y" value for your 50% Red saturation the proper value for each of R80%, G/B465 for the target Gamma?
For sure, if there is any deviation in x/y/Y you will not have linear results. For example if the gamma for Green at 46% is off and "Y" is too high, your x/y for your "50% Red" will be plus green......

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post #581 of 1634 Old 05-11-2009, 07:19 PM
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just for shits and giggles, has anyone tested whether you can make the RS20 more over saturated with the CMS? Can you go plus with the saturation control? I didn't even think to try but am a little curious.

Absence of evidence is not evidence of absence

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post #582 of 1634 Old 05-11-2009, 07:36 PM
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Can anyone post some screen shots after this upgrade and calibration?
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post #583 of 1634 Old 05-11-2009, 10:30 PM
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Tonight I spent a couple of hrs to get the best grayscale I can manage with my I1LT and HCFR; I'm trying to get ready for UMR's visit next week to see how much better he will be able to improve things!

I get the dE's to be all <4, down to 20IRE; they are < 2 in most place, just going up to below 4 at a few points in the middle. (Have 740 hrs on the lamp.) The values I get are Gain (RGB) = 0, -12, -44, and Offset (RGB) = -6, -5, 0. I know that there is a lot of variance with diff pj's, screens, etc., but do these seem reasonable to the rest of you? The CMS settings Ldvd, Lawguy, and Manni all look very nice, very little difference; hard to choose a preference.
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post #584 of 1634 Old 05-12-2009, 04:51 AM
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Quote:
Originally Posted by millerwill View Post

Tonight I spent a couple of hrs to get the best grayscale I can manage with my I1LT and HCFR; I'm trying to get ready for UMR's visit next week to see how much better he will be able to improve things!

I get the dE's to be all <4, down to 20IRE; they are < 2 in most place, just going up to below 4 at a few points in the middle. (Have 740 hrs on the lamp.) The values I get are Gain (RGB) = 0, -12, -44, and Offset (RGB) = -6, -5, 0. I know that there is a lot of variance with diff pj's, screens, etc., but do these seem reasonable to the rest of you? The CMS settings Ldvd, Lawguy, and Manni all look very nice, very little difference; hard to choose a preference.

The biggest visible change for me in switching from the i1LT to the i1Pro was in grayscale. I would be curious to see what umr does for you. Is he doing a REC 709 calibration or his own film-gamut calibration (or both)?

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post #585 of 1634 Old 05-12-2009, 05:04 AM
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Originally Posted by millerwill View Post

Tonight I spent a couple of hrs to get the best grayscale I can manage with my I1LT and HCFR; I'm trying to get ready for UMR's visit next week to see how much better he will be able to improve things!

I get the dE's to be all <4, down to 20IRE; they are < 2 in most place, just going up to below 4 at a few points in the middle. (Have 740 hrs on the lamp.) The values I get are Gain (RGB) = 0, -12, -44, and Offset (RGB) = -6, -5, 0. I know that there is a lot of variance with diff pj's, screens, etc., but do these seem reasonable to the rest of you? The CMS settings Ldvd, Lawguy, and Manni all look very nice, very little difference; hard to choose a preference.

He is coming here in September. Trust me he will have his work cut out. lol
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post #586 of 1634 Old 05-12-2009, 07:46 AM
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Originally Posted by Lawguy View Post

. I would be curious to see what umr does for you. Is he doing a REC 709 calibration or his own film-gamut calibration (or both)?

No idea!
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post #587 of 1634 Old 05-12-2009, 12:45 PM
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Quote:
Originally Posted by Manni01 View Post

...
LDVD, would you mind telling us more about the way you calibrate from the PJ, and which difuser you use?

Hi guys - just getting caught up. I've posted about this many times. EyeOne Pro measured off the screen for "baseline/reference measures". Then Spyder 2 measured about 20" from lens. I tell HCFR to train the Spyder 2 to the EyeOne. I get the color accuacy of the EyeOne combined with the lower light reading capabilities of the Spyder 2 and the ability to measure directly out of the pj lens. I am fairly certain that anyone having problems with blue is due to measurement errors/issues. I don't see any of this.
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post #588 of 1634 Old 05-12-2009, 01:26 PM
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Originally Posted by lovingdvd View Post

EyeOne Pro measured off the screen for "baseline/reference measures".

The problem is getting a good reference measure from the i1Pro off the screen for blue in the first place.

If the reference measurement is good, then why bother with the Spyder and if the off-the-screen measurement is not to be trusted, then how can it stand as a valid reference?

I see how this would be useful for grayscale, where a higher stim reading could be used as a reference for a lower stim reading, but it is not clear to me how this helps with color, where only one stim is being measured.

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post #589 of 1634 Old 05-12-2009, 01:36 PM
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Hi guys,

Does somebody have contrast measurements for the RS20?

I did try to measure the contrast of mine and arrived at 24000. Measured with a Minolta LS-100 on a white paper at about 6 inches from the lens. The black measured something of about 0.040 fL, white 955 fL. I'm using the iris at position -15 (fully closed), zoom about in the middle, calibrated grayscale for D65 (using max gain for red, green and red offset at -1), and using about 50 % of negative (downwards) lensshift (lens at same level as top of the screen).

I'm a bit dissapointed to see only this contrast for a closed iris, compared to what the people measured at http://www.cine4home.de.

Does anybody know what I'm doing wrong? Or is my measurement equipement far from good. Or is the huge negative lensshift making the contrast worse? I don't have the LS-100 for the moment so I can not try if it is due to the shift. Or should I try to measure 0 IRE and 20 IRE close to the lens and 20 IRE and 100 IRE on the screen and calculate from this the contrast?

Thanks for any help,
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post #590 of 1634 Old 05-12-2009, 01:53 PM
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Quote:
Originally Posted by Manni01 View Post

Thanks for the confirmation Dan, these are the ones I use, and yes, I am not aware either of a source for a 75% stim set. Maybe Le Dahu can tell us, as he is the one who requested the data.

Unfortunately I didn't find any source for saturation patterns at 75% stim.
I thought you conducted the full test at 75% including saturations.
So I will produce the patterns and run the test. I will probably write a piece of software since I need more than the 4 usual saturations.
Investigating the old FW, I used the 40 saturation patterns on some occasions! very interesting
Then I will compare both FW behavior on that regard.
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post #591 of 1634 Old 05-12-2009, 02:39 PM
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Quote:
Originally Posted by TomHuffman View Post

The problem is getting a good reference measure from the i1Pro off the screen for blue in the first place.

If the reference measurement is good, then why bother with the Spyder and if the off-the-screen measurement is not to be trusted, then how can it stand as a valid reference?

I see how this would be useful for grayscale, where a higher stim reading could be used as a reference for a lower stim reading, but it is not clear to me how this helps with color, where only one stim is being measured.

Correct we are on the same page. This trained combo is fantastic for grayscale and that's where the real benefit comes from (faster readings, and readings down to 5%).

However when it comes to the gamut measurements and CMS tweaking, I continue to use the trained Spyder rather than switching to the EyeOne. Mainly because of convenience - no stopping for dark readings, no taking down the meter and moving the setup to another meter at the screen, easily able to go back to grayscale measurements and then back to gamut if necessary etc.
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post #592 of 1634 Old 05-13-2009, 04:17 AM
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I took the suggestion of zooming the picture in to get more accurate readings. This works great and blue is now fixed (not that it was that bad before).

I will give it all another go this weekend and post my findings in detail.

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post #593 of 1634 Old 05-13-2009, 10:50 AM
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A somewhat OT question, but things are slow here now so please forgive!

Many of you are using the EyeOne Pro; is this really better than the Chroma5 colorimeter? Also, do you use the 'Home Edition' of Calman, or the 'Enthusiast Edition'? I see that Curt Palme has a special on the Home Edition with Chroma5 of only $389, compared to $875 for it with the I1Pro; quite a diff.

Would appreciate any thoughts of wisdom you have arrived at.
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post #594 of 1634 Old 05-13-2009, 11:12 AM
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Originally Posted by millerwill View Post

Many of you are using the EyeOne Pro; is this really better than the Chroma5 colorimeter?

If I were going to rely on one sub-$1000 meter, it would be the Chroma 5. On standard displays is does nearly as well as well as the i1Pro for color and grayscale and it has much larger dynamic range. Furthermore, it is incredibly easy to use because it requires no dark readings. The i1Pro requires periodic dark readings throughout a calibration session to keep it accurate.

For displays with a non-standard source of illumination--LED, laser, or Xenon, then the i1Pro would be a better choice, but for CRT, plasma, or projectors with UHP bulbs the Chroma 5 is a really good device. LCD, since it has backlighting, can be trickier. On some the Chroma 5 will do fine and on others the i1pro will do better.

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post #595 of 1634 Old 05-13-2009, 11:37 AM
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What would it be about the character of light from a Xenon lamp that would make it more difficult to read than UHP?

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post #596 of 1634 Old 05-13-2009, 12:06 PM
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Quote:
Originally Posted by Lawguy View Post

What would it be about the character of light from a Xenon lamp that would make it more difficult to read than UHP?

I am not entirely sure about the technical background of this. My guess is that these colorimeters are working off of internal calibration tables that were created with these standard illumination sources in mind. With displays whose light source has significantly different spctral characteristics, they can return poorer than usual results.

For example, I found the Chroma 5 was incredibly accurate for the the RS20 and the Planar, but not accurate at all for the Sony Ruby, which uses a Xenon bulb.

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post #597 of 1634 Old 05-13-2009, 12:25 PM
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Tom - Do you ever come up to Toronto? I'm having a hard time finding someone around here that has the equipment needed to properly calibrate the CMS on my RS20. If not, I'm getting married in September in St. Mary's, MD. Wonder if I could drop off my projector before the wedding and pick it back up when I come back from the honeymoon. Don't know how far Rockville is from Baltimore.

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post #598 of 1634 Old 05-13-2009, 12:38 PM - Thread Starter
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Originally Posted by lovingdvd View Post

Correct we are on the same page. This trained combo is fantastic for grayscale and that's where the real benefit comes from (faster readings, and readings down to 5%).

However when it comes to the gamut measurements and CMS tweaking, I continue to use the trained Spyder rather than switching to the EyeOne. Mainly because of convenience - no stopping for dark readings, no taking down the meter and moving the setup to another meter at the screen, easily able to go back to grayscale measurements and then back to gamut if necessary etc.

Thanks for the reply Ric. There is something I don't understand though. Derek from Spectracal says cleary that when training/profiling a meter, the matrix table is only valid as long as the primaries don't change. So is this simply wrong, or have you found a way around it to be able to go on using the trained Spyder 2 on the gamut? When you check with the 1pro, do you get the same gamut as read with the trained spyder after the primaries have changed? Also which revision of thei1prodo you have? I have a revision D and I don't find it slower than the d2, so the main benefit for me is better accuracy for the greyscale below 30IRE.
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post #599 of 1634 Old 05-13-2009, 12:43 PM - Thread Starter
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Originally Posted by Ignace View Post

Hi guys,

Does somebody have contrast measurements for the RS20?

I did try to measure the contrast of mine and arrived at 24000. Measured with a Minolta LS-100 on a white paper at about 6 inches from the lens. The black measured something of about 0.040 fL, white 955 fL. I'm using the iris at position -15 (fully closed), zoom about in the middle, calibrated grayscale for D65 (using max gain for red, green and red offset at -1), and using about 50 % of negative (downwards) lensshift (lens at same level as top of the screen).

I'm a bit dissapointed to see only this contrast for a closed iris, compared to what the people measured at http://www.cine4home.de.

Does anybody know what I'm doing wrong? Or is my measurement equipement far from good. Or is the huge negative lensshift making the contrast worse? I don't have the LS-100 for the moment so I can not try if it is due to the shift. Or should I try to measure 0 IRE and 20 IRE close to the lens and 20 IRE and 100 IRE on the screen and calculate from this the contrast?

Thanks for any help,
Ignace.

This is what I measured when my lamp was 185 hours http://www.avforums.com/forums/dlp-l...ml#post8684427.

Be aware that a small error on the dark reading as a huge influence on the result. You should look at the accuracy range of your meter and interpolate min/max contrast from an average of measures.
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post #600 of 1634 Old 05-13-2009, 12:44 PM
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Ignace,

I have measured about 41,000 to 1 on/off on my RS20 with the iris at 12. Many things could be wrong in your situation.
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