Datacolor User to User Support Group.

I asked this question elsewhere and am hoping someone here on this
list can give me more insight on this set of measurements.

Does anyone know what the mean and standard deviation are for the
Delta-E and Delta-E (a*b*) are for a typical mini ColorChecker chart
from GretagMacbeth?

I'm getting the following when reading with the SpectroColorimeter
from my PrintFIX PRO package:

Patch Delta-E

1 1.0
2 2.0
3 2.1
4 3.5
5 2.9
6 2.4
7 3.2
8 2.0
9 2.4
10 3.8
11 2.7
12 5.6
13 3.7
14 1.9
15 3.9
16 3.5
17 2.7
18 3.3
19 3.1
20 2.3
21 4.0
22 1.6
23 1.8
24 0.4

Some of them look pretty far off but others are spot on. Is this
standard deviation from manufacturing of the color checker chart or
are the pigments used to create the chart somewhat different than what
the Datacolor 1005 can interpret?

Thanks in advance.

Tom, I don't have an answer to your question, but I'm curious if you're
making multiple readings and averaging?  The possibility of a little ambient
light or other error during a single reading might change your results.

It does seem that the 4-5 delta-e measurements are pretty surprising, as
well as the wide variation from patch to patch.

I don't have the colorchecker, so no way to duplicate your work here, sorry.

You might try posting this on the colorsync forum too (or maybe you already
have).

-kris 

> -----Original Message-----
> From: colorvision_group@yahoogroups.com 
> [mailto:colorvision_group@yahoogroups.com] On Behalf Of Tom
> Sent: Thursday, March 02, 2006 8:26 AM
> To: colorvision_group@yahoogroups.com
> Subject: [colorvision_group] GretagMacbeth Mini ColorChecker 
> - Delta-E?
> 
> I asked this question elsewhere and am hoping someone here on 
> this list can give me more insight on this set of measurements.
> 
> Does anyone know what the mean and standard deviation are for 
> the Delta-E and Delta-E (a*b*) are for a typical mini 
> ColorChecker chart from GretagMacbeth?
> 
> I'm getting the following when reading with the 
> SpectroColorimeter from my PrintFIX PRO package:
> 
> Patch Delta-E
> 
> 1 1.0
> 2 2.0
> 3 2.1
> 4 3.5
> 5 2.9
> 6 2.4
> 7 3.2
> 8 2.0
> 9 2.4
> 10 3.8
> 11 2.7
> 12 5.6
> 13 3.7
> 14 1.9
> 15 3.9
> 16 3.5
> 17 2.7
> 18 3.3
> 19 3.1
> 20 2.3
> 21 4.0
> 22 1.6
> 23 1.8
> 24 0.4
> 
> Some of them look pretty far off but others are spot on. Is 
> this standard deviation from manufacturing of the color 
> checker chart or are the pigments used to create the chart 
> somewhat different than what the Datacolor 1005 can interpret?
> 
> Thanks in advance.

--- In colorvision_group@yahoogroups.com, "Kris" <km-yahoo@...> wrote:
> I'm curious if you're making multiple readings and averaging?

I'm taking single readings in this instance.  I have already done a
different personal study on the stability of the measurement device
itself.  I noticed that the device is extremely stable.  I used 150
seperate readings from the white tile taken aproximately 3 seconds
apart and came with a maximim delta-e of 0.5 and one standard
deviation of 0.02.

> It does seem that the 4-5 delta-e measurements are pretty surprising, 
> as well as the wide variation from patch to patch.

Yes .. I thought so also.  One question which occured to me was how
important is it to measure the complete spectrum returned by a sample
vs the several LED lights used in the 1005.  Technicaly if the LEDs
have a spectral distribution which mimics the bell shaped spectral
response curves to which our eyes cone receptors are sensitive ... it
shouldn't make a difference (clever though on the part of ColorVision).

On the other hand if some of the pigments in the ColorChecker chart do
not merely reflect spectral energy but in fact absorb and re-emit them
in different wavelengths (like optical brighteners do) then those 4-5
delta-e measurements would make a lot of sense.

Of course ... it may just be that the Mini ColorChecker isn't that
accurate either ;-)  I have made several profiles with my system and
they are of wonderful quality.  For its design goal the 1005 excedes
my expectations (if you're on the fence go get one ... you'll be happy).

If anyone would like to review my calculations or measurements they
are of course always welcome.  Please let me know and I will forward
you my spreadsheet with the calculations and all the readings.

Thanks for the responses!

This is pulled from the below link...but regarding the Digital ColorChecker Semi Gloss (SG) 
chart:  

"Except for the bluish-green, white and four grey patches, all the other patches are 
relatively far from the original chart colors (with an average DeltaE*ab difference of about 
7 with the standard ColorChecker). "

http://www.babelcolor.com/main_level/ColorChecker.htm#The_problem_with

Danny Pascale of www.babelcolor.com contributed to this thread:

http://forums.robgalbraith.com/showflat.php?Cat=0&Number=363251

Best bet is to post to the Colorsync list and tell us your findings.

John


--- In colorvision_group@yahoogroups.com, "Tom" <ttrostel@...> wrote:

>
> I asked this question elsewhere and am hoping someone here on this
> list can give me more insight on this set of measurements.
> 
> Does anyone know what the mean and standard deviation are for the
> Delta-E and Delta-E (a*b*) are for a typical mini ColorChecker chart
> from GretagMacbeth?

Thanks John!

I suspected the color chart was off by some measure but rather
surprised by the magnitude.  Being a test instrument, under ideal
conditions, it would be nice to hold the delta-e to under 1 (below
normal perception).  That DOES suggest another use for the Spectro
though.  Measure your chart and use THOSE numbers instead of the ones
supplied in the literature.

Thanks again

Tom T

--- In colorvision_group@yahoogroups.com, "John Vitollo" <jvlist@...>
wrote:
>
> This is pulled from the below link...but regarding the Digital
ColorChecker Semi Gloss (SG) 
> chart:  
> 
> "Except for the bluish-green, white and four grey patches, all the
other patches are 
> relatively far from the original chart colors (with an average
DeltaE*ab difference of about 

> 7 with the standard ColorChecker). "
> 
> http://www.babelcolor.com/main_level/ColorChecker.htm#The_problem_with
> 
> Danny Pascale of www.babelcolor.com contributed to this thread:
> 
> http://forums.robgalbraith.com/showflat.php?Cat=0&Number=363251
> 
> Best bet is to post to the Colorsync list and tell us your findings.
> 
> John

In a message dated 3/2/06 8:31:43 AM, ttrostel@... writes:


> Some of them look pretty far off but others are spot on. Is this
> standard deviation from manufacturing of the color checker chart or
> are the pigments used to create the chart somewhat different than what
> the Datacolor 1005 can interpret?
> 

To make this interpretation, you would have to set up some other (laboratory 
grade) device as a standard, and judge the DC 1005 compared to that. Which is 
exactly what is done in testing the 1005 in the first place. The BCRA ceramic 
tile set that Datacolor (and Gretag) use to test their instruments are not 
that different than the ColorChecker in formulation, so there is no reason to 
expect that that accuracy measuring these patches should be much worse than the 
inter-instrument agreement value in the 1005 spec. Given that they are fairly 
similar color sets, I would expect the quoted .4 average and 1.0 max to be 
about right. So there is plenty of slop left over to blame on other things...   
For instance the ColorChecker has been reformulated. so there are batch to batch 
issues. Where did you get your CC reference file? Can you send me your 
reference file, so I can compare it to what I see from various spectros on the Color 
Checker?

thanks,
C. David Tobie
Product Technology Manager
ColorVision Business Unit
Datacolor Inc.
CDTobie@...
www.colorvision.com

> To make this interpretation, you would have to set up some other
(laboratory 
> grade) device as a standard, and judge the DC 1005 compared to that.
Which is 
> exactly what is done in testing the 1005 in the first place. The
BCRA ceramic 
> tile set that Datacolor (and Gretag) use to test their instruments
are not 
> that different than the ColorChecker in formulation, so there is no
reason to 
> expect that that accuracy measuring these patches should be much
worse than the 
> inter-instrument agreement value in the 1005 spec. Given that they
are fairly 
> similar color sets, I would expect the quoted .4 average and 1.0 max
to be 
> about right. So there is plenty of slop left over to blame on other
things...   
> For instance the ColorChecker has been reformulated. so there are
batch to batch 
> issues. Where did you get your CC reference file? Can you send me your 
> reference file, so I can compare it to what I see from various
spectros on the Color 
> Checker?
> 
> thanks,
> C. David Tobie
> Product Technology Manager
> ColorVision Business Unit
> Datacolor Inc.
> CDTobie@...
> www.colorvision.com
>

Thanks for the assistance.  

The only reference material supplied to me with the Mini ColorChecker
card was printed in the pamphlet (CIELAB 2degree D50 Standard
Observer).  I will e-mail you my spreadsheet for reference in a few
moments.  It does go to show you how "reference" color charts can get
pretty far off their published values.  I intend to use the values
supplied to me by the 1005 which are probably much closer to reality!