Re: What is the best Spectrophotometer for reading canvas (Steve Lawrence)
Re: What is the best Spectrophotometer for reading canvas (Steve Lawrence)
- Subject: Re: What is the best Spectrophotometer for reading canvas (Steve Lawrence)
- From: Roger Breton <email@hidden>
- Date: Tue, 01 Apr 2003 11:56:48 -0500
>
Simply put, there are two commonly used geometrys for reflection color
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measurement: 45/0 and D/0. ICC colorimetry is built around the former and the
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latter (aka as integrating sphere) is frequently used in the textile
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industry, among others. 45/0 is appropriate when the sample has a well
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defined gloss component. The idea is that when viewing glossy (or semi-gloss)
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samples, viewers position samples in such a way that the gloss does not
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bounce into the viewers eyes. 45/0 geometry attempts to exclude this specular
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component and instead measure the diffuse component which carries the color
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information. Textile samples generally have a more irregular surface without
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a well-defined specular component. To average out the irregularities, textile
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samples are generally measured diffusely (from all directions). So for these
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samples, sphere geometry may be more appropriate. 45/0 and sphere
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measurements of the same samples generally give different measurements, and
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ICC colorimetry is built around the former, so simply switching to sphere for
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the textile samples may or may not be a fix. Most of the major color
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instrument manufactures have sphere instruments. But since they are intended
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mainly for industrial applications, you may be in for a bit of sticker-shock.
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>
Eric Walowit
>
Tahoe
OK. Provided I had some kind of automated way of reading a TC9.18 RGB target
with a sphere-based instrument, 4mm aperture, do you think that it would
still be possible to end up with a decent colorimetric match, having built
an output profile from sphere-based measurements, and say converting from
AdobeRGB to EPSON_D/0_on_Canvas_RGB? Or, given the radically different
nature of D/0 and 45/0 measurements, that match would be marginally better
than simply averaging readings on canvas using a 45/0 instrument?
Roger Breton
Laval, Canada
email@hidden
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