RE: Correlating Tappi Brightness
RE: Correlating Tappi Brightness
- Subject: RE: Correlating Tappi Brightness
- From: "Mike Eddington" <email@hidden>
- Date: Wed, 5 Aug 2009 12:54:47 -0400
- Thread-topic: Correlating Tappi Brightness
>>Tappi uses an illuminant C type of light source,
>>unlike the tungsten light source used in an EyeOnePro, for instance.
I believe that the illuminant "C" is mathematically equated from the
tungsten illuminant of the measurement device, rather than a true "C"
illuminant in the measurement device. At least that's how it has to be
for our Xrite 938 that measures Tappi brightness. Yes, there would
definitely be a discrepency correlating brightness using illuminant C to
D50 CIELab, which is why I indicated that the measurement device (0/45)
and illuminant would ideally be he same.
>>Personally, I never tried to relate the two measurements
>>mathematically, in Excel, for instance. I live with 72
>>Brightness corresponding to L89 for
>>SWOP5 and 88 Brightness corresponding to L92 SWOP3. I know,
>>far from perfect.
I think brightness on the whole is far from perfect myself. I'm not
really sure why one would even want to correlate brightness to L*a*b*,
jut wondered if it were mathematically possible.
Thanks Roger,
Mike
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