The i1pro Driver

From 22f703cab05b7cd368f4de9e03991b7664dc5022 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=B6rg=20Frings-F=C3=BCrst?= Date: Mon, 1 Sep 2014 13:56:46 +0200 Subject: Initial import of argyll version 1.5.1-8 --- doc/i1proDriver.html | 157 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 157 insertions(+) create mode 100644 doc/i1proDriver.html (limited to 'doc/i1proDriver.html') diff --git a/doc/i1proDriver.html b/doc/i1proDriver.html new file mode 100644 index 0000000..0894f59 --- /dev/null +++ b/doc/i1proDriver.html @@ -0,0 +1,157 @@ + + + + The i1pro Driver + + + + +

How can I +have confidence in the i1pro Driver ?
+

+A question that has been asked is : "You've +written your own driver for the Eye-One Pro. How can I have confidence +that the measurements are accurate, and will match those made with the +original manufacturers driver ?"
+
+This is a quite reasonable question. The following attempts to answer +it.
+

Why does Argyll use it's own +i1pro driver ?

+Primarily because the Original Manufacturers Driver (OMD) isn't +available for all the platforms that ArgyllCMS supports (Linux in +particular). A side benefit is that it's possible to tweak many of the +driver parameters for slightly better results and more flexibility. It +has also helped in understanding the characteristics and limitations of +such instruments.
+

Does it match the OMD ?

+In principle the behaviour should be very similar. While the Argyll +driver has been written from scratch, it does use exactly the same +calibration values from
+inside the instrument, and attempts to use the calibration values and +process the raw instrument readings in an equivalent manner to that of +the OMD.
+
+But the proof of the pudding is in the measuring, so to actually verify +this, the following experiment was conducted:
+
+The Argyll version used was V1.2.0
+
+The Macbeth 24 patch ColorChecker was used as a sample target. For each +patch (and the calibration tile), the following steps were performed:
+
+1) Place the instrument on the calibration tile.
+
+2) Use Argyll spotread to calibrate the Argyll driver.
+
+3) Change drivers to the OMD.
+
+4) Use the OMD to calibrate the instrument.
+
+5) Move the instrument to the patch on the ColorChecker.
+
+6) Read the color using the OMD.
+
+7) Change the back to the Argyll driver.
+
+8) Using the calibration made in step 2), read the color using Argyll.
+
+Each calibration or reading was performed 15 seconds from the previous +one, to put the instrument lamp in a repeatable state.
+The instrument was kept in exactly the same position for calibration +and patch measurement with the two drivers.
+(The whole idea is to reduce all other sources of error, other than the +driver itself.)
+
+This measurement was repeated just once for each patch + the +calibration tile. This was done in one run, and the readings were not +specially selected.
+

Results:

+The following D50 L*a*b* values were recorded for each measurement:
+
+A)    The OMD internally calculated L*a*b* value
+B)    The L*a*b* value calculated by Argyll from the OMD +spectral values.
+C)    The L*a*b* value calculated from the Argyll measured +spectral values.
+D)    The L*a*b* value calculated from the Argyll +Hi-Resolution mode measured spectral values.
+
+A is compare to B, to check +that the spectral to standard observer calculations are equivalent.
+
+    The result was an average Delta E (CIE76) of 0.006, +with a maximum of 0.012.
+
+    This shows that there is very close agreement in the +way spectral values are converted to XYZ and L*a*b*.
+
+B is compared to C to check +that the Argyll driver behaves the same as the OMD.
+
+    The result was an average Delta E (CIE76) of 0.028, +with a maximum of 0.051.
+
+    This shows that the OMD and Argyll driver are in +close agreement in spectral measurement.
+    This error is an order of magnitude smaller than +uniformity induced errors typical in the media being measured.
+
+A is compared to C to check +that the Argyll driver and spectral to XYZ differences don't compound.
+
+    The result was an average +Delta E (CIE76) of 0.026, with +a maximum of 0.048.
+
+    Rather than compounding, any spectral to XYZ +differences tend to cancel +out slightly. This is the bottom line +experimental difference between +the two drivers. The actual underlying difference may in fact be less +than this, but it would be necessary to do multiple test runs to +filter out experimental error.
+
+C is compare to D to check +that the Argyll Hi-Resolution mode is behaving reasonably.
+
+    The result was an average Delta E (CIE76) of 0.158, +with a maximum of 0.353.
+
+    Because the ColorChecker samples have relatively +smooth reflectance spectra, it can be expected that
+    the normal and Hi-Res mode results should be fairly +similar. And indeed, this is the case. The biggest
+    differences are for patches +with the largest spectral transitions in them, which is to be expected +as the
+    Hi-Res measurement more +closely follows the spectral shape, while the differences for +spectrally flat
+    patches is neglegable, since both can follow the +spectral shape well.
+
+Example Yellow-Green Patch, Hi-Res & Normal spectrum:
+ Yellow-Green patch, Hi-Res vs. Normal

+
+

Conclusions:

+The experimental average difference of 0.026 +Delta E76 shown above provides evidence that despite using a completely +different instrument driver to that supplied with the instrument, the +ArgyllCMS Eye-One pro measurement values have comparable accuracy, and +can be relied upon to match measurements made using the original +manufactures driver.
+

Raw Data: