Excel dE calculator for 10-pt grayscale? - AVS Forum
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post #1 of 11 Old 02-14-2010, 07:42 PM - Thread Starter
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Is there an excel calculator for grayscale that allows input of 10-pt grayscale xyY data and then returns dE's in various formulas (CIELUV, CIELAB, and CIE94)? I'd like to be able to calculate CIELAB and CIE94 dE's for grayscale data from ColorHCFR (xyY) without having to do one point at a time.
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post #2 of 11 Old 02-15-2010, 05:18 AM
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Originally Posted by PlasmaPZ80U View Post

Is there an excel calculator for grayscale that allows input of 10-pt grayscale xyY data and then returns dE's in various formulas (CIELUV, CIELAB, and CIE94)? I'd like to be able to calculate CIELAB and CIE94 dE's for grayscale data from ColorHCFR (xyY) without having to do one point at a time.

Tom H's spreadsheet attached to the end of his Basic Guide has this for 20%-100% white readings. I assume he left out 10% because for most folks readings at that level are not going to be considered reliable/accurate.


cheers,


--tom
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post #3 of 11 Old 02-15-2010, 10:07 AM - Thread Starter
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Thanks, I was able to get CIELUV and CIELAB to work, but for some % stimulus values of CIE94, I got the #### (#NUM!) message. Not sure how to fix it, especially since the worksheet is protected. 20, 30, 40, 70, and 80 show this error message, while the remaining ones worked fine.
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post #4 of 11 Old 02-15-2010, 10:49 AM
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Quote:
Originally Posted by PlasmaPZ80U View Post

Thanks, I was able to get CIELUV and CIELAB to work, but for some % stimulus values of CIE94, I got the #### (#NUM!) message. Not sure how to fix it, especially since the worksheet is protected. 20, 30, 40, 70, and 80 show this error message, while the remaining ones worked fine.

What are the xy coordinates that caused the errors?


--tom
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post #5 of 11 Old 02-15-2010, 10:53 AM - Thread Starter
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post #6 of 11 Old 02-15-2010, 11:09 AM
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Originally Posted by PlasmaPZ80U View Post

0.314347, 0.330439 is one example.

Fixed.

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post #7 of 11 Old 02-15-2010, 11:31 AM - Thread Starter
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Originally Posted by TomHuffman View Post

Fixed.

Nice, it works perfectly now. Is the minimal perceptible difference for CIE94 higher than 1.0 for grayscale? Using this formula, I get two points with 1.0 dE and one with 1.3 dE. Those same points are well below 2.5 and 2.0 for CIELUV and CIELAB, respectively.
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post #8 of 11 Old 02-15-2010, 03:02 PM
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Quote:
Originally Posted by PlasmaPZ80U View Post

Nice, it works perfectly now. Is the minimal perceptible difference for CIE94 higher than 1.0 for grayscale? Using this formula, I get two points with 1.0 dE and one with 1.3 dE. Those same points are well below 2.5 and 2.0 for CIELUV and CIELAB, respectively.

CIE94 and CIELAB should be the same for grayscale. CIELUV will be a little higher. What value did you test?

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post #9 of 11 Old 02-15-2010, 03:12 PM - Thread Starter
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Originally Posted by TomHuffman View Post

CIE94 and CIELAB should be the same for grayscale. CIELUV will be a little higher. What value did you test?

I tested 40%, 80%, and 100% using CIE94.

40% (0.312051, 0.327233) 1.0
80% (0.313477, 0.33081) 1.0
100% (0.311976, 0.330588) 1.3

I didn't initially notice that CIELAB and CIE94 were the exact same for grayscale. So, this means a dE under 2.0 for both formulas is ideal for grayscale? I was thrown off by the 1.0 MPD for CIE94.
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post #10 of 11 Old 02-15-2010, 06:54 PM
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Quote:
Originally Posted by PlasmaPZ80U View Post

I didn't initially notice that CIELAB and CIE94 were the exact same for grayscale. So, this means a dE under 2.0 for both formulas is ideal for grayscale? I was thrown off by the 1.0 MPD for CIE94.

For grayscale 2.0 is about as good as it gets, visibly anyway. The MPD of 1.0 for CIE94 is for color only. This is because of the way CIE94 treats the relationship between lightness and chromatic errors. Since grayscale doesn't consider lightness, CIE94 and CIELAB are the same here.

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post #11 of 11 Old 02-15-2010, 06:55 PM - Thread Starter
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