i1 display pro: why does a colorimeter need to be profiled to a display - AVS Forum
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post #1 of 19 Old 11-15-2012, 01:56 AM - Thread Starter
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Hello,

I've just bought one (awaiting delivery) but there is this thing I cannot wrap my head around.

If you profile a colorimeter to a specific display why is this profile only very accurate for that display?

As soon as you know the how much your colorimeter is "off" compared to a good spectro, why bother profiling again (except to compensate for drift over time)?
As an example, so that I get my point across clearly: if I know my plain ruler (colorimeter) always measures 1 mm and my super accurate ruler (spectro. meter) measures 1,2 mm, the compensation is always +0,2 mm.
This does not change when measuring different things (pages, the length of a book, the length of my cell phone, etc..). The compensation will always be +0,2 mm. Of course my plain ruler may bend and get hot and cool down so that, over time, it might need more compensation.

But for colorimeter profling, why would the compensation differ when:

- There is a switch in display type (LCD to plasma for instance)
- You make a change in the CMS. Suppose I profile a colorimeter to RGB full red on a certain display, and I have to offset the colorimeter to +0.010 (just pulling a number out of my hat). Next, I change full red using a CMS . Say I then profile the colorimeter again, the offset may have to be changed to +0,005. Why is this?

Can someone offer an explanation to this:-)?

My gear: Panasonic TH-42PF11EK pro plasma display. -- Iscan Duo video processor -- i1 display 3 colorimeter -- i1 pro 2 spectrometer
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post #2 of 19 Old 11-15-2012, 03:38 AM
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Because the spectral output from displays of the same 'type' can be very different...

And with different displays they can be very, very different.

As a result, a simple offset on not going to be accurate - it may 'help'. but that's not the same.

Steve

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post #3 of 19 Old 11-15-2012, 04:59 AM - Thread Starter
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Thank you Steve. I've already learned a lot from reading on your website (the science part is quite interesting). So if I get it right, colorimeters get calibrated to a spectrum (a spectracal output). And the error a colorimeter has is not linear across the spectrum?

A change with a CMS alters the spectrum and therefore the colorimeter error may (or may not) get larger. But would it be correct to say that CMS work will not change the spectrum of a display significantly? I.E. the changes are so small that reprofiling would technically be the correct thing to do, but the gains in accuracy would be very small.

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post #4 of 19 Old 11-15-2012, 10:47 AM
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Quote:
Originally Posted by Jeroen1000 View Post

Thank you Steve. I've already learned a lot from reading on your website (the science part is quite interesting). So if I get it right, colorimeters get calibrated to a spectrum (a spectracal output). And the error a colorimeter has is not linear across the spectrum?
A change with a CMS alters the spectrum and therefore the colorimeter error may (or may not) get larger. But would it be correct to say that CMS work will not change the spectrum of a display significantly? I.E. the changes are so small that reprofiling would technically be the correct thing to do, but the gains in accuracy would be very small.

The issue is that the spectral output changes from display to display.

So a Dell u2410 monitor has a different signature than a Dell 2408wfp. Both are wide gamut CCFLs, but their spectral signature is slightly different. It's the signatures of the spectrum that is important, Where the peaks and valleys are, not the absolute intensity.

Since the error for colorimeters is in the spectral domain to XYZ conversion, when you change the input spectrum you change the amount of error.

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post #5 of 19 Old 11-15-2012, 02:07 PM
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Joel is totally correct!

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post #6 of 19 Old 11-15-2012, 11:22 PM - Thread Starter
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Thank you both:-)! I'm going to try not to worry about this too much. I'll probably cash up for a i1 pro2 sooner or later. Going to try with the i1 display 3 pro first to get a feel for it. 90% accurate or so is good enough for me.

Joel or Steve, ever profiled before the CMS work and after and compared the colorimeters error? It's not going to be large, but in your opinion, do you think it would be worth it as a final touch up to reprofile the meter to the display after the final CMS adjustments?

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post #7 of 19 Old 11-16-2012, 04:11 AM
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Quote:
Originally Posted by Jeroen1000 View Post

Thank you both:-)! I'm going to try not to worry about this too much. I'll probably cash up for a i1 pro2 sooner or later. Going to try with the i1 display 3 pro first to get a feel for it. 90% accurate or so is good enough for me.
Joel or Steve, ever profiled before the CMS work and after and compared the colorimeters error? It's not going to be large, but in your opinion, do you think it would be worth it as a final touch up to reprofile the meter to the display after the final CMS adjustments?

If you have a spectro in your hand, it takes about 15 seconds to switch meters to the spectro to do the CMS and then there is no issue to check. So use the profiled colorimeter to do Gray scale/gamma and the Specto to do color work. If you only have the colorimeter, you are stuck with tables.. or you could rent an i1pro from sepctracal, profile your meter, do the cms work with the i1pro then recheck the profile just to satisfy curiosity. It will be slightly different, every time you profile CMS change or not, the meters have tolerances and the screen is no where near perfect in consumer products..
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post #8 of 19 Old 11-16-2012, 06:42 AM
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Quote:
Originally Posted by sotti View Post

The issue is that the spectral output changes from display to display.
So a Dell u2410 monitor has a different signature than a Dell 2408wfp. Both are wide gamut CCFLs, but their spectral signature is slightly different. It's the signatures of the spectrum that is important, Where the peaks and valleys are, not the absolute intensity.
Since the error for colorimeters is in the spectral domain to XYZ conversion, when you change the input spectrum you change the amount of error.

So keeps the question have all U2410 the same spectral signature as far as possible or not, as Steve says?
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post #9 of 19 Old 11-16-2012, 07:10 AM
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Originally Posted by fredman2005 View Post

So keeps the question have all U2410 the same spectral signature as far as possible or not, as Steve says?

You have NO way to know if the manufacturer change suppliers of the light source in the middle of a manufacturing run or even if they use only one manufacture to start with. That is why a profile is only good for the display it was made on end of story.

if you have not read this it may answer your questions.
http://www.tlvexp.ca/2012/04/do-calibration-tables-really-work-for-tri-stim-devices/
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post #10 of 19 Old 11-16-2012, 09:56 AM
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The thing to keep in mind is that a spectroradiometer just by the nature of how it works, can measure ANY light source accurately as long as it is within the luminance range the meter can handle. Even though the light spectra delivered by plasma, CCFL LCD, LED LCD, and various projection lamps are very different, a spectroradiometer can read all of them accurately.

Lower-cost (and some moderately expensive) meters use combinations of 3 or 4 up to maybe 10 very specifically selected filters. This type of meter can be made accurate for one very specific light spectrum... that means you could make a colorimeter accurate for plasma, but because CCFL or LED light sources in LCDs produce very different combinations of light (primarily red, green, and blue, but there's variations in the amount of overlap (broadness or narrowness) and amplitude of each color when light sources are different. Those differences cause different readings from colorimeters... for example, if you had a "perfect" plasma display with zero errors and a similar "zero error" LCD panel, a spectroradiometer would produce the same readings for both displays, but a colorimeter would produce different readings for the 2 displays. To make the colorimeter measure the "different" display accurately, you have to provide some sort of correction. And that correction helps the colorimeter compensate for the very likely different light spectra emitted by, say, CCFL or LED-lit LCD displays compared to, say, plasma displays.

If you poke around online, you can find some fairly graphic examples of light spectra emitted by different types of video displays or projectors (and projection lamps). A laser display with red, green, and blue lasers emits only 3 frequencies of light... one for each color. Projection lamps, CCFLs, and LED produce a huge number of different frequencies of light and not all of them have equal amplitude. It's tempting to call the number of frequencies infinite because you can just keep adding decimal places to each discrete frequency to get a slightly different frequency. You could, hypothetically, produce a colorimeter with 4 different filter sets in it... one for plasma, one for CCFL, one for LED, and one for projection lamps and select each filter set as needed. That would be closer, but still wouldn't compensate for variations from display-to-display even if they have the same type of light source. And there are many "flavors" of projection lamps so to be REALLY accurate, even if a colorimeter had multiple filter sets, it could still be made to read better via characterization against a known-good spectro device.

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post #11 of 19 Old 11-16-2012, 10:14 AM
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It all depends on how close the color of the pixels in the display match the color of the filters in the colorimeter. However the color of the sub-pixels can not deviate too much from the CIE standard as almost all video signals are based on those three colors. The other side of the calibration issue is how much the accuracy of the meter really affects the final calibration. If you have a meter that reads to within 1E over a wide range of display types, but those dipslays can not be adjusted to anywhere close to 1E, than the meter error does not matter. In calibration your calibrating instrument only needs to be about ten times more accurate than the unit you are calibrating.

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post #12 of 19 Old 11-20-2012, 03:56 PM
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What's the difference between the OEM and retail version of the D3? Is one version intentionally "crippled"?


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post #13 of 19 Old 11-21-2012, 01:57 AM - Thread Starter
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It only vaguely belongs in this thread but:

see here http://www.chromapure.co.uk/details.asp?id=25&type=blog and here http://store.spectracal.com/home-hardware-support

So basically, both versions are the same hardware. There is not any crippling going on:) The difference lies in the software support.

- OEM version does *not* work with any X-Rite software (including their software for monitor calibration)
- OEM version does work with software that supports it like Chromapure, Calman or Basiccolor.
- Calman also supports the retail version.

I believe vendors have to reach an agreement with X-Rite before being able to support the OEM version. I don't know why Calman can support both the OEM and retail version, and Chromapure cannot.

So, check what software you want to use it with and then decide.

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post #14 of 19 Old 11-21-2012, 06:19 AM
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Quote:
Originally Posted by Jeroen1000 View Post

I don't know why Calman can support both the OEM and retail version, and Chromapure cannot.

Greetings

Probably happens when you pay a boat load of money for this right. ...

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post #15 of 19 Old 11-21-2012, 07:31 AM
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There is not any crippling going on:) The difference lies in the software support.
.

Thanks, Jeroen

I'm trying to decide between CM & CP with a D3. I had read somewhere along the way that CM slowed down (crippled?) a version of the D3? I don't want to make false assumptions against a company I have a lot of respect for; just trying to make the right choice.

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post #16 of 19 Old 11-21-2012, 07:46 AM
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Originally Posted by spongebob View Post

Thanks, Jeroen
I'm trying to decide between CM & CP with a D3. I had read somewhere along the way that CM slowed down (crippled?) a version of the D3? I don't want to make false assumptions against a company I have a lot of respect for; just trying to make the right choice.
bob

Nope we never cripple meters.

You might have seen mentioned a CM crippled version would be the ColorMunki version of the i1 Display Pro, but that one is firmware tweaked at the factory and only works with XRite software as far as I know.

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post #17 of 19 Old 11-22-2012, 06:59 AM
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To verify what has been said above, the Retail version of the i1D3 requires a large payment to X-Rite from other software vendors to enable it's support.

Many software manufacturers have decided against paying the fee, as it is just not commercially viable.
Why X-Rite decided to do this with the i1D3, and no other probe is weird...

But, that's life I guess.

Steve

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post #18 of 19 Old 11-22-2012, 09:45 AM
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Quote:
Originally Posted by Light Illusion View Post

To verify what has been said above, the Retail version of the i1D3 requires a large payment to X-Rite from other software vendors to enable it's support.
Many software manufacturers have decided against paying the fee, as it is just not commercially viable.
Why X-Rite decided to do this with the i1D3, and no other probe is weird...
But, that's life I guess.
Steve

And what is your point. It has already been said before I don't think we needed your confirmation.

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post #19 of 19 Old 11-23-2012, 12:38 AM
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A statement of fact is just that... I see no problem at all?

There is still a lot of confusion regarding the two i1D3 models, and we get a lot of annoyed customers who have purchased the Retail one without knowing the difference or the limitations.

I have spoken at length to X-Rite about this, and they do understand the issue - but having put the sales model in place they are not able to change it now.

Although there is an OEM version of the new i1Pro2 there is no associated limitation with Retail vs. OEM - all models work without restriction.

Steve

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