Re: Accuracy of the Munsell Neutral Value Scale
Re: Accuracy of the Munsell Neutral Value Scale
- Subject: Re: Accuracy of the Munsell Neutral Value Scale
- From: "dpascale" <email@hidden>
- Date: Fri, 16 Apr 2010 14:22:08 -0400
Ben,
I checked a few of the measurements and they are mostly within the i1
maximum inter-instrument agreement (1 DeltaE CIE94).
Note 1: Assuming the manufacturing error is zero!
Note 2: The absolute accuracy of the i1 Pro is worse than the
inter-instrument agreement.
For example, for N5, the "nominal" (from reference info) L*a*b* value of N5
is:
51.6 / -0.05 /0.04 (Illuminant-C or D50)
Note 3: You should not assume that N5 corresponds to L*=50. L* is generally
around 10 * MunsellValue, but this is not an exact relation.
N 4.75/ is in fact very close to L*=49, as you measure.
The error between your measument and the nominal value for N5 is:
0.83 CIEDE94.
Which is quite good.
The error between your measument and the nominal value for N1 is:
1.00 CIEDE94.
Which is also quite good.
The error between your measument and the nominal value for N9 is:
1.54 CIEDE94.
Which is not as good, but the error is mostly in L*. This could be explained
by :
1-The backing used for measurement.
2- A dirty i1 calibration plate. (clean with pure alcohol).
3- The i1 used many times in a row (some models will show slightly increased
luminance when repeating a measurement, especially if ststing with a "cold"
instrument).
4- And the manufacturing tolerance...
Danny Pascale
email@hidden
www.babelcolor.com
----- Original Message -----
From: "Ben Goren" <email@hidden>
To: <email@hidden>
Sent: Friday, April 16, 2010 1:44 PM
Subject: Accuracy of the Munsell Neutral Value Scale
My glossy Munsell Neutral Value Scale arrived yesterday. Of course, the
first thing I did was reach for my i1 Pro and do a few measurements (with
argyllcms spotread).
The values it reports are rather different from the ones printed on the
chart. However, my i1 is some years old and I've yet to have it
recalibrated.
Some examples:
N 0.5/ is D50 Lab: 4.180658 -0.185364 1.322423
N 0.75/ is D50 Lab: 6.727218 -0.200322 0.050625
N 1/ is D50 Lab: 11.487675 -0.402491 -0.030117
...
N 4.75/ is D50 Lab: 49.349451 -0.519980 -0.177740
N 5/ is D50 Lab: 51.722094 -0.871205 -0.120957
N 5.25/ is D50 Lab: 54.136808 -0.771905 0.315211
...
N 9/ is D50 Lab: 92.528793 -0.681620 0.018600
N 9.25/ is D50 Lab: 94.871649 -0.641582 0.500569
N 9.5/ is D50 Lab: 97.289880 -0.757583 0.765509
And a brand-new X-Rite Mini Gray Balance Card is D50 Lab:
51.054682 -0.619076 0.093643
Is it the chart, my i1, or my understanding of the relationship between L*
values and Munsell notation?
I understand the chart isn't intended to be a precision-calibrated
standard, but those variations seem rather larger than I would have
expected for something so finely gradated. For example, the N 4.75/ patch
isn't just closer (according to my i1) to L* = 50 than it is to L* = 47.5,
it's also closer to L* = 50 than the N 5/ patch itself.
Thanks,
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