Colorimeters and Spectrographs, Questions - AVS Forum
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post #1 of 56 Old 08-22-2013, 01:19 AM - Thread Starter
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Hello, I've been doing some research into what my options would be if I took the plunge and bought my first meter. I just had some questions.

Clearly entry level colorimeters are a fair bit cheaper than spectrographs ($150 for C3+CalMAN vs ~$400 for a Munki spectro or $300-400 for a used i1Pro). However, reading up a bit more I'm feeling a bit put off of colorimeters (though at that price, I wish I wasn't feeling put off!).

If I'm understanding correctly, correction tables to account for the filters in colorimeters needing to be adjusted for different TVs could potentially be way off because of production differences in the TVs. So basically, the colors could be way off and I would never know it.

I guess I have two questions about colorimeters:

1) Is it known about how often TVs are well out of line with where the adjusted colorimeter thinks their colors are at? Specifically with Plasmas (or even more specifically, with the LG 42PJ550).

2) Assuming the TV is out line with where the meter thinks it should be, is it known how badly out of line these things are on average? In other words, in this situation, would calibrating the TV with the colorimeter actually make it worse off than using a calibration disc, or could one still reap significant benefits in accuracy over just the disc?


Finally, where do people generally find well priced ($250-300 would be great) used i1Pro meters? Just ebay and the classifieds on this site, or are there some other good, safe sites?

Thanks in advance.
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post #2 of 56 Old 08-22-2013, 07:20 AM
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My suggestion would be to buy fork out the additional money for the i1display (D3) colorimeter and get started with your new hobby. You will get fairly accurate results with color and it will be sensitive enough to read down to the 10% stimulus level. It is a step up from the C3 but more functional as it can be tripod mounted and has more correction tables I believe (Talking D3 that Spectracal sells, I have the C6 which is the same hardware as the D3) After you are comfortable with calibrations (Takes a while) you could add the i1pro to take you the last few % better that can be achieved. It is not an all or nothing situation.
I got my use i1pro by monitoring the Spectracal forum and each day. Another member was selling his gear. This way you know it is in good shape, in fact all I had to do was call Spectracal and give them the serial and they changed the records for the unit to my information,. as they had originally sold it. Other places to look are the Classified here on AVS and of course fleabay.
Good luck with your new hobby!
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post #3 of 56 Old 08-22-2013, 09:57 AM
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Quote:
Originally Posted by cb220 View Post



Finally, where do people generally find well priced ($250-300 would be great) used i1Pro meters? Just ebay and the classifieds on this site, or are there some other good, safe sites?

Thanks in advance.

You would be better off with a I1D3 Series vs the C3 (which is older generation) but you would be better off starting with an Spectro. I can't tell you how many have started with a i1D3 only to figure out very quickly they needed a Spectro and added one. If you are on a budget and only want one meter right now, get a Spectro. Be patient, i1Pro Rev D's show up on the used market in various places, I know of four of my users who picked them up in August.

From your post, you may have already read the following in another Thread:

I always recommend a i1Pro (i1 Pro 2) Spectrometer, even a used i1Pro Rev D ($250-$450) is great. ColorMunki Spectro is my 2nd recommendation.

Why a Spectro, see why here:

http://www.avsforum.com/t/1373556/i1-pro-or-d3-if-you-could-only-have-one-meter

http://www.tlvexp.ca/2012/04/do-calibration-tables-really-work-for-tri-stim-devices/

And Read these Threads:
http://www.avsforum.com/t/1449310/eye-one-pro-or-display-3-pro

http://www.avsforum.com/t/1464411/what-would-you-rather-have-for-display-calibration

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post #4 of 56 Old 08-22-2013, 10:07 AM
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Greetings

Read this article on the effectiveness of calibration tables.

Closer to the end of the article, there is a bit about how the incorrect answers tend to be always in the same direction. You can use this part to determine how you visually know when something might be amiss. When the tables fail on you, the error makes the image way redder looking than it should be.

That's one of those funny things ... the moment you decide to buy a $250-300 D3 colorimeter, it gets you in striking distance of a used i1 pro.

Don't forget about the learning curve. The hardware and software do not sprout magical hands that do this for you. You still have to go research the process of calibration. It can take hundreds of hours of real time ... spread out over the course of a year. Or you can always bypass the steep learning curve by paying for real video training. This gets you to the end result of a calibrated TV a lot faster and you can be more confident that what you learned was correct.

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post #5 of 56 Old 08-22-2013, 12:05 PM - Thread Starter
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Thank you all for your replies.

I have indeed seen those links you've posted in other topics, turbe, and especially the article Michael wrote is what made me skeptical of colorimeters.

Seeing as the D3 is being suggested over the C3 that does change the price points, like Michael said if I'm spending $250 on a D3 it's not a far leap if I can find a low priced used i1Pro. I would feel better about the accuracy of a spectro over a colorimeter. I also think I've read that the i1Pro has very little drift over a long time, which could actually make it "cheaper" than a colorimeter that has to be sent in for expensive re-calibrations. I do wonder how lucky I would have to be to find a used i1Pro that is more in my price range (closer to $300 than $400). Looking around at a few different forum marketplaces I mostly am seeing a thread selling an i1Pro popping up every few months, and usually in the high $300's or $400's. Still, even at $400 it is something I would be strongly considering.

On the other hand, I assume the D3 would take readings a lot faster than the i1Pro and I hear black readings can take quite a long time with the i1Pro. For a beginner like myself taking a long time on readings could be frustrating since I'll probably be trying a lot of different things and it would be nice to have that go faster.

Michael, the tests on the LG in your article were indeed disappointing with just the calibration tables. If I'm reading the tables correctly it looks like where the Jeti read around 2 dE at 100% intensity, the C6 with just calibration tables was reading around a 9, a difference of 7. I was very interested in your suggestion of shifting the C6 300-500K to possibly shave 2 or 3 dE off of that, which could bring the difference between them to 4. I've read that differences of 3 or more dE can be seen by the human eye, so it would still be a noticeable difference between the Jeti and C6 and thus not a perfect solution by any means, but I wonder just how noticeable it is to someone who isn't looking very closely.

All of this gives me a lot to think about. For now I think I'll try and be patient and keep a look out for a lower priced used i1Pro, as that does seem to be the best long term solution, but I am also quite interested in the D3.

Thank you again, everyone, for your advice.
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post #6 of 56 Old 08-22-2013, 12:25 PM
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I originally had an i1pro and I don't think you can go wrong with it as a good place to start. After a while, however, I did start to be dissatisfied with its low light performance. I wanted to have a good gamma at low light levels to improve shadow detail, and the i1pro's difficult there made my results untrustworthy. Certainly not a show-stopper, but enough to make me covet a colorimeter to fill in the gap as it were. So after I had been doing this for a few years I added a D3 so I could have the best of both worlds.
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post #7 of 56 Old 08-22-2013, 12:55 PM
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yes, he can always add the i1D3 in the future, perhaps a budget for next year.. For anyone just having one meter, a Spectro like a i1Pro Rev D, which is still used by many Professionals in the field today, is the way to go.

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post #8 of 56 Old 08-22-2013, 01:53 PM
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Quote:
Originally Posted by Michael TLV View Post

Greetings

Read this article on the effectiveness of calibration tables.

Closer to the end of the article, there is a bit about how the incorrect answers tend to be always in the same direction. You can use this part to determine how you visually know when something might be amiss. When the tables fail on you, the error makes the image way redder looking than it should be.

That's one of those funny things ... the moment you decide to buy a $250-300 D3 colorimeter, it gets you in striking distance of a used i1 pro.

Don't forget about the learning curve. The hardware and software do not sprout magical hands that do this for you. You still have to go research the process of calibration. It can take hundreds of hours of real time ... spread out over the course of a year. Or you can always bypass the steep learning curve by paying for real video training. This gets you to the end result of a calibrated TV a lot faster and you can be more confident that what you learned was correct.

regards
Michael, I cannot reproduce these results. Looking just at the 90% point (you said the errors where the greatest at the top end), here's what I got compared to what you got using a stock i1D3 with no corrections at all.



It looks to me that the problems you are seeing are with the specific correction tables being used. Notice that they are not randomly off but consistently reading too blue. The fact that they are significantly worse than what I am seeing with a stock, uncorrected i1D3, suggests that the problem lies with the tables themselves, not in some general flaw with colorimeter correction.

Could you test this again?

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post #9 of 56 Old 08-22-2013, 02:34 PM
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Greetings

Tom,

The article simply tells people to beware. I have no control over the tables that are used. They are what they are.

No one starts out by telling us that their tables are faulty. Everyone says things are just fine. So the problem becomes ... who's version of the truth is the truth. My version ... your version ... their version ... ? And that is the point.

Of course I was not using a D3 to do these tests so your tables were not used.

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post #10 of 56 Old 08-22-2013, 02:59 PM
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Quote:
Originally Posted by Michael TLV View Post

Greetings

Tom,

The article simply tells people to beware. I have no control over the tables that are used. They are what they are.

No one starts out by telling us that their tables are faulty. Everyone says things are just fine. So the problem becomes ... who's version of the truth is the truth. My version ... your version ... their version ... ? And that is the point.

Of course I was not using a D3 to do these tests so your tables were not used.

Regards
Michael, I wasn't using any correction tables at all. It was the stock i1D3 in LCD read mode. Do you have any uncorrected retail or OEM D3s around to test?

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post #11 of 56 Old 08-22-2013, 03:10 PM
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Hi Tom,

Unfortunately not. Sorry. I'm not part of anyone's test team.

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post #12 of 56 Old 08-22-2013, 06:27 PM
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Quote:
Originally Posted by TomHuffman View Post

Michael, I cannot reproduce these results. Looking just at the 90% point (you said the errors where the greatest at the top end), here's what I got compared to what you got using a stock i1D3 with no corrections at all.



It looks to me that the problems you are seeing are with the specific correction tables being used. Notice that they are not randomly off but consistently reading too blue. The fact that they are significantly worse than what I am seeing with a stock, uncorrected i1D3, suggests that the problem lies with the tables themselves, not in some general flaw with colorimeter correction.

Could you test this again?
I find it interesting that the D3 without any corrections has respectably low errors compared to your reference Jeti, especially compared to the C6 using correction tables. I would be interested to see how the D3 measures a PDP compared to a Jeti (or reference meter), and also how much the generic corrections provided by X-Rite improve things.
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post #13 of 56 Old 08-22-2013, 07:06 PM
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Great idea for a thread. Maybe our ISF experts will chime in here. I would like to learn more about the gear used to provide those calibrations!
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post #14 of 56 Old 08-22-2013, 08:08 PM
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Quote:
Originally Posted by rahzel View Post

I find it interesting that the D3 without any corrections has respectably low errors compared to your reference Jeti, especially compared to the C6 using correction tables. I would be interested to see how the D3 measures a PDP compared to a Jeti (or reference meter), and also how much the generic corrections provided by X-Rite improve things.
Not much different. The errors are maybe a little larger. I am seeing errors in the 0.003-0.006 range. These are worth correcting, but the errors are not as big as what Michael saw in the 0.005-0.012 range. The fact that his corrected errors are larger than the uncorrected errors I generally see is what leads me to believe that there was something wrong with the test, which is why I commented.

I should add that the i1D3 errors I see now are lower than what I saw when it was first released and several months afterwards. They have gotten better over time--not hugely, but I see a general trend in a positive direction. I have measured hundreds of these meters, so I am pretty confident of what they are capable of.

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post #15 of 56 Old 08-22-2013, 09:13 PM
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Quote:
Originally Posted by TomHuffman View Post

Not much different. The errors are maybe a little larger. I am seeing errors in the 0.003-0.006 range. These are worth correcting, but the errors are not as big as what Michael saw in the 0.005-0.012 range. The fact that his corrected errors are larger than the uncorrected errors I generally see is what leads me to believe that there was something wrong with the test, which is why I commented.

I should add that the i1D3 errors I see now are lower than what I saw when it was first released and several months afterwards. They have gotten better over time--not hugely, but I see a general trend in a positive direction. I have measured hundreds of these meters, so I am pretty confident of what they are capable of.
Just for clarification, when you say that there's not much difference and that the errors are a little higher, are you referring to how Plasmas measure with the D3 compared to your Jeti? Or the errors are a bit higher using X-Rite's generic correction tables? I'm assuming the former.

Thanks.
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post #16 of 56 Old 08-22-2013, 09:19 PM
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Quote:
Originally Posted by rahzel View Post

Just for clarification, when you say that there's not much difference and that the errors are a little higher, are you referring to how Plasmas measure with the D3 compared to your Jeti? Or the errors are a bit higher using X-Rite's generic correction tables? I'm assuming the former.
Yes, the former.
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post #17 of 56 Old 08-22-2013, 10:35 PM
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Quote:
Originally Posted by rahzel View Post

I find it interesting that the D3 without any corrections has respectably low errors compared to your reference Jeti, especially compared to the C6 using correction tables. I would be interested to see how the D3 measures a PDP compared to a Jeti (or reference meter), and also how much the generic corrections provided by X-Rite improve things.

Actually the C6 LED table is the i1D3 base table, the wide gamut LED, LED RGB, and LCD RGBY LED are unique correction tables to the C6. The enhanced tables are the additional ones, we do a NIST certification the LED table to make sure the meter is up to spec, but the differences posted above are down to procedure process and individual displays rather than a difference in the hardware tables.

One of the gotcha's when comparing a C6/i1D3 to a Jeti have very different field of views, so unless you've accounted for that you are guaranteed to see larger differences.
http://store.spectracal.com/article-why-viewing-angle-is-important
http://www.jeti.com/cms/index.php/instruments-55/radiometer/specbos-1211

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post #18 of 56 Old 08-24-2013, 02:50 PM
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Originally Posted by sotti View Post

One of the gotcha's when comparing a C6/i1D3 to a Jeti have very different field of views, so unless you've accounted for that you are guaranteed to see larger differences.

I believe the article Michael wrote has an addendum with varying distances for the Jeti (it's at the end of the article).



On a separate note, the White LED tables (standard and wide gamut) seem to be quite accurate on three Samsung LED-LCDs I've measured... the EH5000, EH6000, and EH6030. Interestingly, the error while quite small is towards (reading) too much blue in the grayscale.
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post #19 of 56 Old 08-25-2013, 12:56 AM
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Originally Posted by cb220 View Post

On the other hand, I assume the D3 would take readings a lot faster than the i1Pro and I hear black readings can take quite a long time with the i1Pro. For a beginner like myself taking a long time on readings could be frustrating since I'll probably be trying a lot of different things and it would be nice to have that go faster..

Actually the i1Pro is faster at low levels than you might think ... the real issue is repeatability @ low levels ... and the need to do a "dark calibration" every 10 to 15 minutes. At a certain point (you'll know when) it becomes too wibbly-wobbly to really trust. On my LCD, that would be the 10% stimulus level ... on displays with better black levels, that point may be equivalent to 20% stimulus.

On my last 10pt, BT1886 run, I profiled my much maligned D2 and used that to get chromaticity "close" and gamma/luminance dialed in, then I made another pass through with the i1Pro to touch up the chromaticity (D65 whitepoint) ... and continued with the i1Pro for the CMS work. Then I watched my reference material and enjoyed an adult beverage or two ... wink.gif

The moral of the story, is that you'll probably eventually wind up with at least two meters anyway, so where you start from is pretty much dealer's choice.

Edit: I realize, the technique I described above is not optimal in any way ... and in fact may produce "dubious" results, but there's only so much you can do with stone knives and bear skins. wink.gif
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post #20 of 56 Old 08-25-2013, 09:28 AM
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Actually the i1Pro is faster at low levels than you might think ... the real issue is repeatability @ low levels ... and the need to do a "dark calibration" every 10 to 15 minutes. At a certain point (you'll know when) it becomes too wibbly-wobbly to really trust. On my LCD, that would be the 10% stimulus level ... on displays with better black levels, that point may be equivalent to 20% stimulus.

On my last 10pt, BT1886 run, I profiled my much maligned D2 and used that to get chromaticity "close" and gamma/luminance dialed in, then I made another pass through with the i1Pro to touch up the chromaticity (D65 whitepoint) ... and continued with the i1Pro for the CMS work. Then I watched my reference material and enjoyed an adult beverage or two ... wink.gif

The moral of the story, is that you'll probably eventually wind up with at least two meters anyway, so where you start from is pretty much dealer's choice.

Edit: I realize, the technique I described above is not optimal in any way ... and in fact may produce "dubious" results, but there's only so much you can do with stone knives and bear skins. wink.gif

I used to use the i1pro a lot directly in the past because I was too lazy to do a proper multi-pass profile, but now I just use my profiled C6 for the entire calibration... if I want to ensure the profile is still working, I just do some spot checks with the i1pro.

In short, profiling is more practical and convenient in the long run since the C6 needs no dark readings and can handle the dark end faster (and more importantly) with greater accuracy below 10 cd/m^2 or so.
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post #21 of 56 Old 08-25-2013, 11:09 AM
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Originally Posted by PlasmaPZ80U View Post

I used to use the i1pro a lot directly in the past because I was too lazy to do a proper multi-pass profile, but now I just use my profiled C6 for the entire calibration... if I want to ensure the profile is still working, I just do some spot checks with the i1pro.

In short, profiling is more practical and convenient in the long run since the C6 needs no dark readings and can handle the dark end faster (and more importantly) with greater accuracy below 10 cd/m^2 or so.

Agreed, but the software I use doesn't really do "multi-pass" profiling, so I suppose the results are always a bit "suspect." ... OTOH, it's pretty quick. wink.gif

BTW, if anyone still cares, my 2.5 year old D2 is still "linear," but is now reading anywhere from 6 to 9 dE off from the i1Pro. (It sees too much green, which skews the un-profiled calibration toward too much blue/red.)
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post #22 of 56 Old 08-30-2013, 11:09 AM
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Originally Posted by JimP View Post

It would seem to me (after spending the $$$$ for a i1pro2) that it's more cost efficient to just get a profiled i1display3 pro to start with. You're more likely to get accurate results with a profile coming directly from true reference grade equipment than you are going through an intermediary. You'll have one less device to break and someday when the tech moves on, you won't feel as bad replacing it.

you'd need the profiled colorimeter to be profiled for your actual displays, not general ones of each display type/tech and you'd need to re-profile every six months or so to compensate for colorimeter drift
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post #23 of 56 Old 08-30-2013, 11:09 AM
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What kind of display do you have?

This is why your following statement,
Quote:
It would seem to me (after spending the $$$$ for a i1pro2) that it's more cost efficient to just get a profiled (colorimeter) to start with. You're more likely to get accurate results with a profile coming directly from true reference grade equipment than you are going through an intermediary. You'll have one less device to break and someday when the tech moves on, you won't feel as bad replacing it.

doesn't really work. Now, if you were to carry a Minolta or Jeti around with you ...

Think about it for a minute: If you have a dozen "factory profiles" to choose from, what you (the end user) really has is just a one in twelve chance that the profile you wind up using will be "correct" for the display you are calibrating, which would seem to be worse than having having no profile at all. wink.gif

Edited since the originally quoted post was deleted.
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post #24 of 56 Old 08-30-2013, 12:19 PM
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Originally Posted by JimP View Post

Tell me about the level that is used to calibrate the level you use? How certain can you be that a $1,200 ish spectro is that accurate for all display types? It's a trick question because I recently had my i1pro2 compared to a Klein K10's calibration. It wasn't as close as I would have thought. Still within dE3 on grayscale but just barely. Green saturation was low which apparently is a weakness of the i1pro2 when it comes to reading plasma. Then again, how do I really know that the K10 wasn't off and the i1pro2 is the more correct one. See the vicious circle?

I think in theory, you're right. I'm just not convinced anymore that in practice that it really works out that way.

I'd say the reason to trust a spectro over a colorimeter with tables is that a spectro is designed to be able to handle all kinds of display types and light sources by design whereas the colorimeter is relying on general tables (by display type/light source) which approximate the target displays's SPD. In short, it's making an educated guess/approximation whereas the spectro is actually measuring the spectral response itself.

If you are going to compare your i1Pro2 to a reference, it should be a reference spectro, not a high-end colorimeter with tables (unless those tables were custom made for your display in the last six months or so).
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post #25 of 56 Old 08-30-2013, 12:28 PM
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For clarity, why would someone pick an LED table (1 of 12) if they're calibrating a plasma? Maybe I'm not understanding what you're saying. Please elaborate.

They would not. However, if you were to measure the spectral output of 10 different LED TVs you could very possibly get 10 different readings. If you profile your Colorimeter on each TV using a spectro, you will get accurate readings. If you use the 1 generic profile that comes with the meter, your readings may not be correct on any of the TVs.
These errors can be minor but the can also be large enough to make the end result worse than before you started..
This article explains the issue and with charts and numbers.
http://www.tlvexp.ca/2012/04/do-calibration-tables-really-work-for-tri-stim-devices/
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post #26 of 56 Old 08-30-2013, 02:23 PM
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O.K.....you're starting to sway me.


I know I've read about this before on these threads and as you can imagine, some say that a tweaked colormeter works fine and others argue against it. You've probably seen these same discussion.

Exactly Jim, a colorimeter is display dependent so uses tables typical of its genre..
If your display is typical of the one the table was made for great.

If it was not then ....

Thats why the spectro is used to check not the colorimeter but your display.

Chicken and egg really, thats why I bought my spectro because of that nagging doubt.
As it happened, they were very close when checked but what if....
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post #27 of 56 Old 08-30-2013, 11:14 PM
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For clarity, why would someone pick an LED table (1 of 12) if they're calibrating a plasma? Maybe I'm not understanding what you're saying. Please elaborate.

I'll refer you to airscapes' post. But leave you with a counter question, "How do you know that the 'plasma' profile wouldn't be the best choice for a specific LED display?" ... Conversely, how do you *know* that LED table #10, wouldn't be the best choice for your plasma?"

PS: I actually made a "small" mathematical error ... the odds of "success" in my scenario would be more like 1 in 13, since there's always the possibility that *none* of the profiles would be "correct." Or even 1 in 14 since there's always the possibility that using *no* profile would be the best choice.
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post #28 of 56 Old 08-31-2013, 06:53 AM
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How many examples have you come across "first hand" where these tables are as you suggest?

Did you read this article? http://www.tlvexp.ca/2012/04/do-calibration-tables-really-work-for-tri-stim-devices/

For the 2 displays Michael tested in his home with the C6 tables, one was very close, the other Not so close at all. This subject has been hashed over many times, and if you are interested in the best possible outcome, you need to either use a spectro by itself (inexpensive units will not read accurately much below 20-30% stim) or a colorimeter that you profile with a spectro to each display. There are no calibrations police,so if the budget only allows for a colorimeter get and and you can add the spectro later if the constant wondering if it is accurate bothers you like it did myself us! smile.gif
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post #29 of 56 Old 08-31-2013, 10:08 AM
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Greetings

I used the Jeti spectro to verify a student's calibration with the c6 last weekend in a class on a $400 LG set. It was within dE of 1 -1.5 across the board. I was initially surprised, but remembered that this set was LCD ccfl based ... like my panasonic LCD set. The tables are pretty good here.

Unfortunately, my article plays the role of the terrorist. People making the tables are claiming they are good for everything and I just have to show a few that are not so good ... (and I don't have to try hard either) ...

Regards

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ISF/THX/TLV Video Instructor
The Video Calibration Education Hub - www.TLVEXP.com

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post #30 of 56 Old 08-31-2013, 10:45 AM
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The first thing that comes to mind is that plasma displays light distribution is different than an LED's therefore the tables for each should work best for their own.

How many examples have you come across "first hand" where these tables are as you suggest?

You're missing the point, which is this:

Mathematically speaking, adding more and more "calibration tables" in the interest of "improving accuracy" only *increases* the uncertainty that your measurements will be "accurate," unless, of course, it were actually possible to profile *every* single display model (and any sub-models with differing parts, for instance, my LCD display model has at least three different variants - all using the same model number.)

PS: You *can* try to land aircraft using an aneroid barometer that hasn't been re-calibrated or compared to a reference instrument in the past six months, but it's not really "recommended." wink.gif

PPS: I'm just saying that if you recognize that a colorimeter is *not* accurate enough to use without a correction "table," then you must also recognize the need to (re)correct the colorimeter before *every* calibration run. (Especially, since in this case, you don't really even know if you're measuring the atmospheric pressure on Earth or Venus.)
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