1994.09.16 07:05 "Re: TIFF ReferenceBlackWhite Field Versus Leffler's TIFF Software", by Fredrik Lundh
Page 86 of the TIFF 6.0 Specification says that the number of entries in the ReferenceBlackWhite field should be 6. However, the manual page for TIFFSetField says that there should be 2*SamplesPerPixel entries. What gives?
Maybe the section heading, "RGB Image Colorimetry," gives a hint ;-)
The tags described in that section deal with RGB calibration issues (reference points, transfer functions, etc). And the spec explicitly says that the ReferenceBlackWhite tag is to be used with RGB and YCbCr images only. So if you find this tag in a file, SamplesPerPixel ought to be 3.