Official JVC RS20 / HD750 Calibration and CMS thread (NEW FIRMWARE V1.1) - Page 46 - AVS Forum
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post #1351 of 1634 Old 02-21-2010, 07:33 AM - Thread Starter
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Hi there,

A good first step resource is Curt Palme's greyscale calibration for dummies here : http://www.curtpalme.com/forum/viewtopic.php?t=10457
Then when it's time to move to gamut calibration, check all the links in the first post (especially the section calibration tips, and Tom Huffman's excellent tutorial).

Good luck!
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post #1352 of 1634 Old 03-21-2010, 02:39 PM
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This thread has been awfully quiet; maybe all us RS20 owners have our units happily calibrated. I have mine done by UMR (Jeff Meier) with very good results.

However I'm now over a 1000 hrs on my second lamp, so that calibration is not terribly relevant at this point. And I have really been wanting to do this myself. So I recently got Tom Huffman's new ChromaPure calibration package, and had a ball with it and wanted to let you all know about it. It's great for a relative novice like me, and gives a very user friendly hand-holding guide through grayscale, full CMS, and custom gamma. It also gives very straight-forward guide for 'training' a higher quality (but slow) meter like the EyeOne Pro to a faster meter, such as the Display LT, the two meters I have. I had used HCFR before to do grayscale, but had not ventured into the CMS game. I'm sure that the knowledgeable gurus amongst you can do all this with HCFR (or Calman), both of which I have, but I find ChromaPure to be much simpler and intuitive to use. Anyway, this is my experience.
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post #1353 of 1634 Old 03-21-2010, 03:01 PM
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Quote:
Originally Posted by millerwill View Post

This thread has been awfully quiet; maybe all us RS20 owners have our units happily calibrated. I have mine done by UMR (Jeff Meier) with very good results.

However I'm now over a 1000 hrs on my second lamp, so that calibration is not terribly relevant at this point. And I have really been wanting to do this myself. So I recently got Tom Huffman's new ChromaPure calibration package, and had a ball with it and wanted to let you all know about it. It's great for a relative novice like me, and gives a very user friendly hand-holding guide through grayscale, full CMS, and custom gamma. It also gives very straight-forward guide for 'training' a higher quality (but slow) meter like the EyeOne Pro to a faster meter, such as the Display LT, the two meters I have. I had used HCFR before to do grayscale, but had not ventured into the CMS game. I'm sure that the knowledgeable gurus amongst you can do all this with HCFR (or Calman), both of which I have, but I find ChromaPure to be much simpler and intuitive to use. Anyway, this is my experience.

Thanks for the input. I just got a b-stock RS20 from AVS and had Jason calibrate it so I could see it in all its glory right out of the box. But this pj had only 7 hours on the bulb so I know this calibration's not going to last for long. I'm interested in doing calibrations myself too and have used HCFR with the $140 i1 but am frustrated with the lack of low light response. So I'm interested in changing my methodology which may include upgrading to the Pro.
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post #1354 of 1634 Old 03-21-2010, 03:21 PM
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Good to see you're getting on well with Chromapure. I found it really helped me sort out my gamma much quicker than HFCR (as it can be done in real time while I make adjustments at each 10 IRE interval). I only recently got (external) CMS to play with, but again Chromapure made this literally about a 30 minute adjustment for me (once greyscale & gamma is adjusted). However, I have to confess that having accurate colour after being used to oversaturated colour is a bit like getting used to coffee with no sugar in it for me. I've slightly nudged up the main colour control on my HD350 after appling the CMS corrections in my VideoEQ Pro as I prefer it this way (stands back and waits to be flamed ).

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post #1355 of 1634 Old 03-21-2010, 03:21 PM
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What # of hours on a lamp do people think is a reasonable amount of time for a professional "touch-up" calibration?

Obviously, if you are DIY you can whenever you want (time permitting).
Just wondering based on value.

Mike
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post #1356 of 1634 Old 03-21-2010, 03:48 PM
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Quote:
Originally Posted by Mike_WI View Post

What # of hours on a lamp do people think is a reasonable amount of time for a professional "touch-up" calibration?

Obviously, if you are DIY you can whenever you want (time permitting).
Just wondering based on value.

Mike

It really depends on how interested one is in getting into doing this themselves. Happily, I'm close to retirement and have more time for hobbies like this and am quite interested in learning to do it. And Chromapure is quite reasonable ($200 for the SW, plus the cost of the meter, which is < $150 for the Display2LT), i.e., altogether less than 1 ISF calibration.
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post #1357 of 1634 Old 03-21-2010, 11:53 PM
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Mike .. in my past experience with JVC and lamps, I noticed that lamps become more stable e realable around the 100 hours, so this could be the age time to get a professional ISF calibration
Anyway, I noticed too the it will needs to be re-touched after the 350-450 hours, but surely after the 500 hours if you need the best and reference results.
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post #1358 of 1634 Old 03-24-2010, 09:42 AM
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I've had a strange problem: in using the new ChromaPure video calibration package with my RS20 I've gotten everything to work fine (and boy, is the CMS a charm to use--so accurate and so simple!) EXCEPT the Custom Gamma step. After running the gamma 'base line' measurement, when I go to a specific IRE, e.g., 90%, and start 'Continuous Measurement', when I bump the gamma up in the custom gamma feature on RS20 up just one point, it jumps to an enormous value, i.e., from ~ 2.2 or 2.3 up to ~ 5 or 6, and the gamma curve just goes straight up! I'm clearly doing something wrong, not understanding what's going on.

In the RS20 custom gamma, I'm selecting 'White' before going to the point by point gamma adjustment. Should I be doing something else? Thanks for any suggestions/advice.

Bill
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post #1359 of 1634 Old 03-24-2010, 12:50 PM
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Quote:
Originally Posted by millerwill View Post

I've had a strange problem: in using the new ChromaPure video calibration package with my RS20 I've gotten everything to work fine (and boy, is the CMS a charm to use--so accurate and so simple!) EXCEPT the Custom Gamma step. After running the gamma 'base line' measurement, when I go to a specific IRE, e.g., 90%, and start 'Continuous Measurement', when I bump the gamma up in the custom gamma feature on RS20 up just one point, it jumps to an enormous value, i.e., from ~ 2.2 or 2.3 up to ~ 5 or 6, and the gamma curve just goes straight up! I'm clearly doing something wrong, not understanding what's going on.

In the RS20 custom gamma, I'm selecting 'White' before going to the point by point gamma adjustment. Should I be doing something else? Thanks for any suggestions/advice.

Bill

The good news is that with great care, patience, and time - you can use the custom gamma menu in the RS20 to dial in the gamma. And although it may take you several hours, it is worth every bit of it when you see what a huge difference this will make (flat picture otherwise after the pj gets a few hundred hours on it, if not sooner).

The not so good news is that the custom gamma menu is extremely finicky and you have to understand its quirks and how to "trick it" into using the values you want. It does not work well for setting one point at a time, measuring, and setting the next point. Rather it works best if you know all the numbers you want to set in advance.

The best thing I can recommend at this point is to search for leDahu's spreadsheet that he posted here months ago. That contains one way to calculate and calibrate gamma all in one run through, rather than one point at a time, which plays well to how the custom gamma menu tweaks work best. Around the same time as that posting, leDahu also posted a text file with instructions on how to manipulate ("trick") the custom gamma menu into using the values you want. A must read for sure.

The other not so good news is that the gamma calibration drifts MUCH quicker than most people realize. For instance in my case I can tweak for 6-7 hours to get the gamma nearly perfect. However within a short amount of bulb hours the calibration and gamma has already drifted, negating a great deal of all the work I had just done. My advise is to get it close but not worry about getting it perfect, and plan to do it often. Its a ton of work but well worth the effort.
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post #1360 of 1634 Old 03-24-2010, 04:43 PM
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Thanks, as always, for your good advice, l'dvd. I actually like the RS20's preset gamma A. It stays very close to 2.3 across most IRE, dipping down to ~ 2.1 at 10%, thus giving better resolution of the features in the darkest scenes. So I may simply not sweat customizing Gamma and going this route.

It is correct, isn't it, to choose 'White' when trying to use the point-wise customization in the RS20?
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post #1361 of 1634 Old 03-24-2010, 06:04 PM
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Quote:
Originally Posted by millerwill View Post

Thanks, as always, for your good advice, l'dvd. I actually like the RS20's preset gamma A. It stays very close to 2.3 across most IRE, dipping down to ~ 2.1 at 10%, thus giving better resolution of the features in the darkest scenes. So I may simply not sweat customizing Gamma and going this route.

It is correct, isn't it, to choose 'White' when trying to use the point-wise customization in the RS20?

I would be quite surprised if one of the standard gammas (such as Gamma A you mentioned) has not drifted considerably, knowing that you have at least a few hundred hours on your unit.

My guess is that if you measure this gamma, you will see that it falls off deeply starting around the 80% range and by 95% is nearly off the chart.
The proper way to see this is on a gamma chart (not on the luminance histogram which shows an exponential curve).

If you can measure your gamma and post the gamma chart here I would like to see it. Unless your gamma is indeed still in tact I would highly recommend correcting it with leDahu's process. It will restore the deep dimensionality to the picture.

To answer your question about RGB in the gamma versus W, the answer is that it depends. Technically speaking if the dE is correct at a certain level but the gamma is not, you can use just W to correct the gamma. However there is typically some interaction, so tweaking W may cause the dE to shift. In which case you can compensate by tweaking RGB accordingly. However in doing so, that can cause the gamma to shift, either back toward the way it was or in the other direction. So like many things calibration-wise it can be a delicate balancing act.
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post #1362 of 1634 Old 03-24-2010, 07:37 PM
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Originally Posted by lovingdvd View Post

I would be quite surprised if one of the standard gammas (such as Gamma A you mentioned) has not drifted considerably, knowing that you have at least a few hundred hours on your unit.

My guess is that if you measure this gamma, you will see that it falls off deeply starting around the 80% range and by 95% is nearly off the chart.
The proper way to see this is on a gamma chart (not on the luminance histogram which shows an exponential curve).

If you can measure your gamma and post the gamma chart here I would like to see it. Unless your gamma is indeed still in tact I would highly recommend correcting it with leDahu's process. It will restore the deep dimensionality to the picture.

To answer your question about RGB in the gamma versus W, the answer is that it depends. Technically speaking if the dE is correct at a certain level but the gamma is not, you can use just W to correct the gamma. However there is typically some interaction, so tweaking W may cause the dE to shift. In which case you can compensate by tweaking RGB accordingly. However in doing so, that can cause the gamma to shift, either back toward the way it was or in the other direction. So like many things calibration-wise it can be a delicate balancing act.

I have over 1000 hrs on this lamp. When I select gamma A, it measures ~ 2.3 +/- .05 from 20 to 100%, but falls to ~ 2.1 at 10%.

Yes, I did see your and leDahu's discussions several weeks ago, but I'm afraid it was mostly beyond me. That's why I find ChromaPure so appealing, it's simplicity.

What I find so weird is how the point-wise gamma adjustment is so wildly sensitive when I try to move the gamma value by the minimal increment. Either ChromaPure is not reading what I think it's reading in its 'Continuous Measurement' mode, or something else.
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post #1363 of 1634 Old 03-24-2010, 08:46 PM
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Quote:
Originally Posted by millerwill View Post

Either ChromaPure is not reading what I think it's reading in its 'Continuous Measurement' mode, or something else.

Bill, as I pointed out earlier, all the program is doing is doing is reading the light output at whatever level of stimulus the test pattern provides.

It just sounds like your unit's custom gamma controls are too sensitive for fine adjustments. Try it again and ignore the gamma position and just take note of the change in output level (cd/m2 or fL). How much does it change when you move the custom gamma control a single click? You can also test this in the raw data module.

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post #1364 of 1634 Old 03-24-2010, 09:01 PM
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Originally Posted by TomHuffman View Post

Bill, as I pointed out earlier, all the program is doing is doing is reading the light output at whatever level of stimulus the test pattern provides.

It just sounds like your unit's custom gamma controls are too sensitive for fine adjustments. Try it again and ignore the gamma position and just take note of the change in output level (cd/m2 or fL). How much does it change when you move the custom gamma control a single click? You can also test this in the raw data module.

Yes, thanks, Tom. I was simply 'trolling' to see if there were some RS20 owners who had successfully used its pointwise gamma function with ChromaPure, to give me some tips.
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post #1365 of 1634 Old 03-24-2010, 11:35 PM
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Originally Posted by millerwill View Post

Yes, thanks, Tom. I was simply 'trolling' to see if there were some RS20 owners who had successfully used its pointwise gamma function with ChromaPure, to give me some tips.

I have calibrated several of these and have not run across this problem. I wouldn't assume that you are doing anything wrong. It just sounds like your unit has a problem.

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post #1366 of 1634 Old 03-25-2010, 01:43 AM
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I used the spreadsheet posted back on the first page of this thread to work out what my custom gamma values should be and it still took me ages sorting it out. Since I've got my VideoEQ Pro I've just set the custom gamma to default and used the controls in the VideoEQ to set gamma (like Millerwill I'm using Chromapure) step by step down from 95 IRE. It's so much easier than the JVC controls, so I'm more likely to do it frequently. Side benefit is that I can shift my gamma in 0.1 increments by simply changing the JVC's custom gamma using a default 2.1/2.3 or whatever setting.

If only the JVC controls were as easy to use, I found them very frustrating given how quickly the gamma drifts.

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post #1367 of 1634 Old 03-25-2010, 11:57 AM
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Quote:
Originally Posted by TomHuffman View Post

I have calibrated several of these and have not run across this problem. I wouldn't assume that you are doing anything wrong. It just sounds like your unit has a problem.

Very interesting, Tom. So when you use the Custom gamma feature of the RS20's, where you can move the gamma value pointwise, I assume that you first click W (white), and not R, G, or B, right? And when you move gamma up or down at one IRE point, this moves in the 'Continuous Measurement' mode of ChromPure, accordingly?
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post #1368 of 1634 Old 03-25-2010, 02:23 PM
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Quote:
Originally Posted by millerwill View Post

Very interesting, Tom. So when you use the Custom gamma feature of the RS20's, where you can move the gamma value pointwise, I assume that you first click W (white), and not R, G, or B, right? And when you move gamma up or down at one IRE point, this moves in the 'Continuous Measurement' mode of ChromaPure, accordingly?

Yes. I have never had any problems here. I did one fairly recently.

I recommend that you experiment as I suggested earlier. Go into the raw data module. Take a reading at, say, 90% stim. Record the Y value. Take another reading after moving the custom gamma up or down one click at the 90% point. How much different are the Y values?

I agree with others that the gamma drifts, but I have not seen this very large change with only small changes in adjustment.

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post #1369 of 1634 Old 03-26-2010, 10:21 AM
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Observation: I know that it is recommended to calibrate by taking light readings off the screen, but I have recently done grayscale and CMS on my RS20 (using ChromaPure) two ways, 1) taking the readings with a Display2LT, trained to my I1Pro, off the screen, and 2) taking the readings directly from the RS20, with the I1Pro about 2-3 ft away (with its diffuser cap on, of course).

The GS and CMS #'s are similar, though of course not identical, and when looking at test material I find that I actually prefer the results from method (2). I would be curious to know what other people's experiences are on this issue. (FWIW, I note that when UMR calibrated my RS20 originally, he took readings directly from the pj!)
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post #1370 of 1634 Old 03-26-2010, 01:53 PM
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Quote:
Originally Posted by millerwill View Post

Observation: I know that it is recommended to calibrate by taking light readings off the screen, but I have recently done grayscale and CMS on my RS20 (using ChromaPure) two ways, 1) taking the readings with a Display2LT, trained to my I1Pro, off the screen, and 2) taking the readings directly from the RS20, with the I1Pro about 2-3 ft away (with its diffuser cap on, of course).

The GS and CMS #'s are similar, though of course not identical, and when looking at test material I find that I actually prefer the results from method (2). I would be curious to know what other people's experiences are on this issue. (FWIW, I note that when UMR calibrated my RS20 originally, he took readings directly from the pj!)

The diffuser that comes with the I1 isn't any good for grey scale. The image will be shifted towards red way too much. You need to point it at the screen without the diffuser if using an I1 probe. I liked the results much more pointed at the projector but using a Spyder2 probe for grey scale. The light intensity is much higher and you get better results visually. My screen is an angular refective high gain model and each RGB level shifts too much pointing the probe off axis. Pointed at the screen doesn't work with my screen.

Ron
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The diffuser that comes with the I1 isn't any good for grey scale. The image will be shifted towards red way too much. You need to point it at the screen without the diffuser if using an I1 probe. I liked the results much more pointed at the projector but using a Spyder2 probe for grey scale. The light intensity is much higher and you get better results visually. My screen is an angular refective high gain model and each RGB level shifts too much pointing the probe off axis. Pointed at the screen doesn't work with my screen.

Ron

Would a good diffuser from a photo shop work with the i1 if a good optical seal can be made to the edges of the i1? I'd like to calibrate directly from the pj too but have heard of this i1 diffuser problem before.
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post #1372 of 1634 Old 03-26-2010, 02:07 PM
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My screen is a Dalite HP, retro-reflective. And as noted, UMR (Jeff Meier) used an I1Pro with diffuser and took readings from the pj.
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post #1373 of 1634 Old 03-26-2010, 02:11 PM
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Would a good diffuser from a photo shop work with the i1 if a good optical seal can be made to the edges of the i1? I'd like to calibrate directly from the pj too but have heard of this i1 diffuser problem before.

Maybe but I would think you still need to have it calibrated with the diffuser for best results. If you find one let me know. Pointing the I1 at the projector is not stable. RGB shifts too much with very small movement of the I1.
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Originally Posted by millerwill View Post

My screen is a Dalite HP, retro-reflective. And as noted, UMR (Jeff Meier) used an I1Pro with diffuser and took readings from the pj.

Maybe the newer models have better diffusers! My screen was noticable red when I used the diffuser.
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post #1375 of 1634 Old 03-26-2010, 02:40 PM
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Originally Posted by Ronomy View Post

Maybe the newer models have better diffusers! My screen was noticable red when I used the diffuser.

As noted, I done with the I1Pro/diffuser from the pj, and off the screen (with a DisplayLT trained to the I1Pro), and though the two are very similar, I slightly prefer the former.
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post #1376 of 1634 Old 03-26-2010, 02:46 PM
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Quote:
Originally Posted by millerwill View Post

The GS and CMS #'s are similar, though of course not identical, and when looking at test material I find that I actually prefer the results from method (2).

There is nothing wrong with taking measurements from the lens using a diffuser. It does allow higher light levels. However, if you do so the readings should be color corrected from measurements taken off the screen. Otherwise, part of your results will be artifacts introduced by the diffuser and you will miss whatever contribution the screen's own characteristics impart to the image.

This is not a rigid recommendation about standards so much as simple common sense. When you watch content, you are watching light that is reflected off the screen, not light that comes out of the lens filtered through a diffuser.

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post #1377 of 1634 Old 03-26-2010, 02:55 PM
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Originally Posted by TomHuffman View Post

There is nothing wrong with taking measurements from the lens using a diffuser. It does allow higher light levels. However, if you do so the readings should be color corrected from measurements taken off the screen. Otherwise, part of your results will be artifacts introduced by the diffuser and you will miss whatever contribution the screen's own characteristics impart to the image.

This is not a rigid recommendation about standards so much as simple common sense. When you watch content, you are watching light that is reflected off the screen, not light that comes out of the lens filtered through a diffuser.

Tom, what you say is obviously correct and certainly makes sense. I specifically asked UMR about this when he calibrated my pj almost a year ago, and he said that the effect of the screen was minimal and less than the inherent errors in the calibration process. These comments may have been specific to my type screen; I would certainly expect a gray screen, e.g., to have a noticeable effect.
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post #1378 of 1634 Old 03-26-2010, 02:57 PM
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Originally Posted by TomHuffman View Post

There is nothing wrong with taking measurements from the lens using a diffuser. It does allow higher light levels. However, if you do so the readings should be color corrected from measurements taken off the screen. Otherwise, part of your results will be artifacts introduced by the diffuser and you will miss whatever contribution the screen's own characteristics impart to the image.

This is not a rigid recommendation about standards so much as simple common sense. When you watch content, you are watching light that is reflected off the screen, not light that comes out of the lens filtered through a diffuser.

Well, sure... I was willing to assume the screen is white, even if it isn't... close enough. But I like the idea of measuring the screen [EDIT] through the diffuser [/EDIT] to correct for them. This can be done at bright levels where the cheap i1 works as well as it can. Then the screen corrected i1 can be turned to the pj for the lower level measurements.


I assume Chromapure has a facility for entering this adjustment measurement?
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post #1379 of 1634 Old 03-26-2010, 04:24 PM
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I specifically asked UMR about this when he calibrated my pj almost a year ago, and he said that the effect of the screen was minimal and less than the inherent errors in the calibration process.

This is testable. What the difference in xy readings using a 80% white test pattern when measured from the lens with diffuser and then taken directly off the screen without diffuser?

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post #1380 of 1634 Old 03-26-2010, 04:25 PM
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I assume Chromapure has a facility for entering this adjustment measurement?

Sure.

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