RE: purpose of Granger rainbow chart?
RE: purpose of Granger rainbow chart?
- Subject: RE: purpose of Granger rainbow chart?
- From: Marco Ugolini <email@hidden>
- Date: Mon, 8 Mar 2010 12:38:42 -0500 (EST)
Matthew Ward wrote:
>> A Granger Rainbow is designed not to have any 'tonal discontinuities'
>> but to show where things like profiles 'fail' and create them.
>> Mathematically it is a completely smooth transition, when it has been
>> through an imaging system it is not, and shows where the 'breakdowns'
>> occur.
In case this had not been specified earlier, and to avoid misunderstandings, I would like to point out that the proper way to test the Granger Rainbow [GR] image file with a custom RGB ICC profile is to ASSIGN the custom RGB profile to the GR file, NOT CONVERT.
In other words, once it's been created (in RGB), and as long as the color space to be tested is also in the RGB color mode, the GR should NOT be converted.
Also, when assessing the custom profile on screen after the custom RGB profile has been assigned, one should always keep in mind that (a) the profiled display's ability to show all the colors in the file without clipping a portion of them is probably limited, in most cases, by the display's often relatively narrow gamut; and that (b) the true test of the custom profile's integrity and proper functioning is to PRINT the GR to the intended inkjet printer and then assess the printed output, rather than relying on what is seen on the display.
As for testing custom CMYK ICC profiles, the only way to use the GR with those is to CONVERT, of course.
Marco Ugolini
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