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Author Topic: i1Pro weirdness & fix  (Read 16890 times)

GWGill

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i1Pro weirdness & fix
« on: February 16, 2016, 07:19:35 pm »

I've been tending to use my i1Pro Rev E (i.e. i1Pro2) for random spot
measurements a lot. Recently it's accuracy had been niggling at me.

What I noticed was this: From cold, do a calibrate.
Measure spots. The errors would rise (literally the L* was rising).

The closer the measurements together, the faster the errors would rise.
Let it cool, and the errors would drop. Recalibrate hot, and the error
would increase as it cooled down.

At its worst, I was seeing errors of 2.0 Delta E between cold and hot!

[ It's pretty easy to replicate this experiment - ArgyllCMS spotread
  makes it straightforward, but you could do something similar with
  ColorPort etc., repeatedly measuring the white calibration tile.

  I noticed this type of thing before with one of the i1pro Rev A's I've
  got, but it wasn't as extreme, and I put it down to being an old lamp
  in a well used instrument. ]

Then it got weirder. This characteristic didn't seem stable. I started
looking at how it was affecting strip measurements, and it kept changing.
Sometimes it would get better. Then it would get worse again.

Then the light went on (so to speak), and I arrived at a theory.

What if the lamp is a miniature Quartz Halogen lamp ?
This would make sense in terms of how long the lamp should last,
QH lamps typically last 2-5 times longer than conventional
incandescent lamps, and would also be helpful in ensuring constant light
output over the lamp life, something that is rather desirable for
an instrument light source. I measured a color temperature of
just over 3000K, which is consistent with a hotter QH lamp.

QH lamps work on the basis of re-circulating evaporated
tungsten back onto the filament. To do that they have to get hot enough to
evaporate any that gets deposited on the inside of the glass, and even hotter
to disassociate the resulting halide back into tungsten at the filament.

If the spot measurement gets the bulb hot enough to evaporate
tungsten from the filament and the glass, but not quite hot enough
to deposit it back at the same rate onto the filament, then the glass
will build up a layer of tungsten on it. This reduces light output.
As it warms up a bit, the tungsten gets evaporated from the glass,
increasing light output. When it gets cold again the tungsten
gets deposited back on the glass. Hence my increasing L* error
as the instrument warms up, and hot/cold behavior.

But if the bulb gets warmer still, say by being used for strip
readings, then the tungsten gets re-deposited on the filament,
and the bulb gets "cleaned". So after some extended strip readings
(i.e. several measurements in a row, made with the button down
and the lamp on for as long as possible), the instrument no longer
displays such dramatic error increases with temperature. In fact
after "cleaning", the worst I could get was 0.08 Delta E, a 20x reduction,
and back in line with instrument specifications.

If you predominantly use your i1Pro for reading strips, you
probably haven't noticed this effect at all, because your lamp
isn't getting dirty.

I've seen similar effects on all my i1Pro's, and also Spectrolino's,
although none as dramatic as the Rev E was.

So if you do lots of spot measurements with your i1Pro's, and get the
impression that your accuracy and consistency of measurement is getting
squirrelly, you may be right. But there is a way of fixing it! 

[ Also posted to the ColorSync mailing list. ]
« Last Edit: February 16, 2016, 09:28:32 pm by GWGill »
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Mark D Segal

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Re: i1Pro weirdness & fix
« Reply #1 on: February 16, 2016, 08:08:58 pm »

What is the way of fixing it? Paying X-Rite a fortune of money for "service"? I wonder how prevalent this problem is - i.e. whether generic or specific to your device.
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Mark D Segal (formerly MarkDS)
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AlterEgo

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Re: i1Pro weirdness & fix
« Reply #2 on: February 16, 2016, 08:40:02 pm »

So if you do lots of spot measurements with your i1Pro's, and get the
impression that your accuracy and consistency of measurement is getting
squirrelly, you may be right. But there is a way of fixing it! 

so for example if I take my i1Pro2 (relatively new and never used to read strips/charts - only spot measurements and probably less than 5000 clicks total so far), calibrate it once ("cold") and then do for example 100 sequential spot measurements of a single patch (granted spots will fluctuate because of the manual placing) with say 1-2 sec delay between measurement I shall see some clearly detectable L* drifting ?
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AlterEgo

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Re: i1Pro weirdness & fix
« Reply #3 on: February 16, 2016, 08:41:59 pm »

What is the way of fixing it?
firmware can (at the expense of the lamp life ?) just detect that you are not readings strips and force lamp heating to keep tungsten balance.
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GWGill

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Re: i1Pro weirdness & fix
« Reply #4 on: February 16, 2016, 09:36:05 pm »

so for example if I take my i1Pro2 (relatively new and never used to read strips/charts - only spot measurements and probably less than 5000 clicks total so far), calibrate it once ("cold") and then do for example 100 sequential spot measurements of a single patch (granted spots will fluctuate because of the manual placing) with say 1-2 sec delay between measurement I shall see some clearly detectable L* drifting ?
Use the calibration tile if you want to measure the D.E. change.
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AlterEgo

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Re: i1Pro weirdness & fix
« Reply #5 on: February 16, 2016, 10:22:05 pm »

Use the calibration tile if you want to measure the D.E. change.
you mean use the same tile that is used for instrument calibration for the spot measurements ? but if there is an error because of this tungsten vapor flow then it shall be clearly seen on any patch as well (granted brighter patches are better), no ?
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GWGill

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Re: i1Pro weirdness & fix
« Reply #6 on: February 17, 2016, 01:12:44 am »

What is the way of fixing it? Paying X-Rite a fortune of money for "service"? I wonder how prevalent this problem is - i.e. whether generic or specific to your device.

1) I suspect only a few people will have seen this problem.
2) If you discover you are one of these people, I described exactly how to fix it.
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GWGill

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Re: i1Pro weirdness & fix
« Reply #7 on: February 17, 2016, 01:14:30 am »

you mean use the same tile that is used for instrument calibration for the spot measurements ? but if there is an error because of this tungsten vapor flow then it shall be clearly seen on any patch as well (granted brighter patches are better), no ?
Yes, but measuring random patches is no way to diagnose problems!

You diagnose accuracy problems by measuring something that is known and consistent, like the calibration tile.
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Mark D Segal

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Re: i1Pro weirdness & fix
« Reply #8 on: February 17, 2016, 07:13:49 am »

1) I suspect only a few people will have seen this problem.
2) If you discover you are one of these people, I described exactly how to fix it.

Where did you describe exactly how to fix it? Maybe I'm missing something, but I re-read your opening post twice and I found ample description of the problem and your hypothesis about why it occurs - most interesting - but I did not see how to fix it.
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Mark D Segal (formerly MarkDS)
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samueljohnchia

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Re: i1Pro weirdness & fix
« Reply #9 on: February 17, 2016, 07:21:19 am »

But there is a way of fixing it!

Please kindly enlighten! A friend has done a similar experiment and shown the i1Pro to be unstable in scan mode for the first 16 passes or so. The L* drops steadily, instead of rises, from the first measurement pass until around the 16th pass, then holds fairly stable from that point onwards. That's a brilliant theory about why we are noticing the inconsistencies in measurements! I think it very well may be the truth. So how should we go about fixing the problem? Depress the i1Pro button to activate the lamp continuously for a certain amount of time to heat the lamp sufficiently until it's 'cleaned'? Then begin measurements and do not pause for too long between measurements?
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GWGill

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Re: i1Pro weirdness & fix
« Reply #10 on: February 17, 2016, 08:11:16 am »

Where did you describe exactly how to fix it?

"So after some extended strip readings
(i.e. several measurements in a row, made with the button down
and the lamp on for as long as possible), the instrument no longer
displays such dramatic error increases with temperature."

60 seconds accumulated "on" time seems a good place to start.
I wouldn't recommend doing this unless you need it, and
can verify that it helps - there is no point in running down the
lamp life for no reason.
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Mark D Segal

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Re: i1Pro weirdness & fix
« Reply #11 on: February 17, 2016, 08:13:21 am »

"So after some extended strip readings
(i.e. several measurements in a row, made with the button down
and the lamp on for as long as possible), the instrument no longer
displays such dramatic error increases with temperature."

60 seconds accumulated "on" time seems a good place to start.
I wouldn't recommend doing this unless you need it, and
can verify that it helps - there is no point in running down the
lamp life for no reason.

Ah, OK, thanks.
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Mark D Segal (formerly MarkDS)
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GWGill

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Re: i1Pro weirdness & fix
« Reply #12 on: February 17, 2016, 08:25:26 am »

A friend has done a similar experiment and shown the i1Pro to be unstable in scan mode for the first 16 passes or so. The L* drops steadily, instead of rises, from the first measurement pass until around the 16th pass, then holds fairly stable from that point onwards.
A steady cadence is a workaround for the problem, but you have to do dummy reads until it stabilizes.

I notice the L* dropping with successive measurements when it is "dirtying" the lamp (assuming my theory is correct), which seems to happen more dramatically for measurements longer than normal spot readings. I've only tested 1 - 5 seconds as doing this, and I'm not sure at what length measurement it stops "dirtying" and start "cleaning".
Quote
Depress the i1Pro button to activate the lamp continuously for a certain amount of time to heat the lamp sufficiently until it's 'cleaned'?
I wouldn't use lamp life up without good reason.
Quote
Then begin measurements and do not pause for too long between measurements?
Maybe that can help.
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Mark D Segal

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Re: i1Pro weirdness & fix
« Reply #13 on: February 17, 2016, 08:30:38 am »

Or maybe press X-Rite to make an instrument that works properly?
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Mark D Segal (formerly MarkDS)
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NickXavi

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Re: i1Pro weirdness & fix
« Reply #14 on: February 18, 2016, 01:23:08 pm »

Or maybe use the i1Diagnostics?

i1Diagnostics when checking the instrument also set some parameters if necessary.

Good luck.
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Doug Gray

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Re: i1Pro weirdness & fix
« Reply #15 on: February 18, 2016, 05:33:12 pm »

I have 3 I1 spectros. One, an M0, is almost 10 years old. I have a uv Cut that is about 6 years old and an I1P2 about a year old. On a colorchecker the oldest has average dEs of about .9 compared to the I1P2 and the uV cut is about .5 dEs different.

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NickXavi

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Re: i1Pro weirdness & fix
« Reply #16 on: February 19, 2016, 04:17:00 pm »

I tested my i1Pro 2 Rev E (3 months old) in cold and hot without recalibration, also I retested without recalibration after measured 540 patches, I compared the measurements from the previous day with the current in every way.

Measurements were made with 10 single point measurements and analyzed with i1Profiler

Always against the tile.

In all comparisons the Delta E 2000 is always less than 0.01.
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GWGill

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Re: i1Pro weirdness & fix
« Reply #17 on: February 19, 2016, 10:35:05 pm »

In all comparisons the Delta E 2000 is always less than 0.01.
Maximum or average ?

None of my 4 i1Pro's are that consistent with regard to warming up. At their best I get DE76 of 0.07.
My Spectrolino is about the same or slightly worse.

With carefully controlled cadence, I can get consecutive measurements that are consistent to 0.003 - 0.008 DE76, but the change with consecutive measurements causing warming up is always worse than that.

[ Others have reported similar observations to mine on the ColorSync list. ]

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NickXavi

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Re: i1Pro weirdness & fix
« Reply #18 on: February 20, 2016, 08:03:21 am »

First of all, on all comparisons the Delta E 2000 is always less than 0.1, not 0,01, sorry for the mistake.

I sent a copy of the  i1Profiler's screen few minutes ago, in which ten measurements made yesterday after 75 minutes of heating and 544 patches measured are compared with ten measurements made today after only one minute of heating, with totally cold instrument.

Always against the tile.

Two questions arise:

** Have you checked your i1Pro with i1Diagnostics?, this software when checking the instrument also modify some parameters if necessary: http://www.xrite.com/product_overview.aspx?Action=support&ID=766

** All my measurements were performed with i1Profiler software. Perhaps the software performs any correction ?. I suggest that you take the same test with i1Profiler

Last, my i1Pro 2 today have a lamp burning time of 8.762.2 seconds.

Good luck!

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samueljohnchia

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Re: i1Pro weirdness & fix
« Reply #19 on: February 20, 2016, 08:06:49 am »

With carefully controlled cadence, I can get consecutive measurements that are consistent to 0.003 - 0.008 DE76, but the change with consecutive measurements causing warming up is always worse than that.

[ Others have reported similar observations to mine on the ColorSync list. ]

Surely you don't mean 0.003 - 0.008? If I can get 0.03 - 0.08 I would be delighted. I'm mostly seeing 0.1 deltaE2ks with my i1Pro 2 Rev E.
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