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Re: "Visual Color Difference" chart [Re: (no subject)]
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Re: "Visual Color Difference" chart [Re: (no subject)]


  • Subject: Re: "Visual Color Difference" chart [Re: (no subject)]
  • From: <email@hidden>
  • Date: Tue, 16 Jan 2007 23:36:01 -0500

Terry,

Here is yet another way to define a target:

Define a color list such as:

L C h
83,8 65,4 116
85,8 65,4 116
87,8 65,4 116
85,8 57,8 116
85,8 65,4 116
85,8 73,6 116
85,8 65,4 112,5
85,8 65,4 116
85,8 65,4 119,5

In this example, the reference is Pantone 374 C with L*C*h* coordinates of 85.8/65.4/116 (D50). I have selected the L*C*h* representation because it is best suited for an error target such as this one. (I will not elaborate here on how to get Pantone L*C*h* values since this is not the topic.)

The reference appears three times in the list. The first three colors represent a variation in Lightness, the next three a variation in Chroma, and the last three a variation in hue.

The values have been adjusted to represent a DeltaE of "almost exactly" 2 with reference to CIE94 (not CIELAB).

This file was made with Microsoft Excel and exported as a TAB delimited format, but it could have been written with Text Edit (Mac) or WordPad (Windows).

Copy the ten lines above and paste in TextEdit or WordPad (the Tabs are now spaces, but do not change them, and no need to change the decimal separator to periods). Open the file with PatchTool, dowloaded from
http://www.babelcolor.com/main_level/download.htm


If you click on a patch in the middle row then move the mouse over the other patches, you will see the DeltaE in the "Info" window (select CIE94 for the color difference).

I have attached an exported images in JPEG(sRGB) but TIFF-Lab 8 and 16 bit is also possible. (Note: you cannot export an image in the trial mode).

In order to fine-tune the above list, I simply opened it in PatchTool and looked at the CIE94 color difference. A few iterations were required to get the final values.

Of course, when you get the target image you want, you still need to print it and measure it for conformance. A few iterations may be required there also, even for a "calibrated" printer. And, as mentioned in a previous post, you should have controlled viewing conditions as metamerism can play games when comparing a printed target with manufactured items.

Danny

email@hidden
www.BabelColor.com

On Fri, 12 Jan 2007 09:15:39 -0500
 Terry Wyse <email@hidden> wrote:

On Jan 12, 2007, at 8:35 AM, Graeme Gill wrote:

Terry Wyse wrote:

It would be awesome if someone could come up with a calculator that would calculate all the possibilities for a delta e of <x> away from a reference. Humm...I may have to do some poking around and see what can be done.

How could you do that, given that are an infinite number ?

Well, I was thinking it could be limited to a certain "resolution" or precision. For my purposes, limiting it to whole Lab integers or one decimal place would be enough.


Terry

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References: 
 >(no subject) (From: "Rick" <email@hidden>)
 >"Visual Color Difference" chart [Re: (no subject)] (From: Klaus Karcher <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Martin Orpen <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Martin Orpen <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Klaus Karcher <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Terry Wyse <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Graeme Gill <email@hidden>)
 >Re: "Visual Color Difference" chart [Re: (no subject)] (From: Terry Wyse <email@hidden>)

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