Hi,
Looking at at those lab values, it seems that there is something
wrong. You cannot get a reflective lab value with an L value greater
than 100.
So either:
The spectroeye needs calibrating.
You are using relative white Lab values
I don't think changing the Illuminant, Angle, or Polarization would
ever give those values.
Lee Badham
Hi All
I too am interested in this subject. It seems that the vast majority
of
papers we use as a book publisher are not matching the ISO12647-2
Type 1
paper colour target of L95 a0 b-2 (white backing)
One one hand we are stating that we require all our printers to now
print to
FOGRA39 but then asking them to print on a range of different papers
which
may or may not be matching the paper white for that standard.
Is this a case of double 'standards'?
Some tests done on common papers we use with a SpectroEye
stora 115gsm - L99.25 a-0.36 b-0.31 - ?E 4.6
lumisilk 130gsm - L100.54 a0.1 b-2.14 - ?E 5.5
sappi quatro matt art 115gsm - L99.6 0.a71 b-2.14 - ?E 4.7
Hi-Q matt art 128gsm - L99.94 a-0.59 b-0.91 - ?E 5.1
As I understand it ISO12647-2 has a max ?E of 3 so in truth all
these papers
fail!
I am using the Bodoni pressSIGN software to assess colours on press
sheets
which apparently has an allowance built in for different paper
colours. I'm
told it will sample the paper colour and then adjust the target
colours
slightly so we can still have a useful test whilst allowing for
papers that
stray outside the standard. Is this the intelligent way to get
around this
real life problem or actually going to introduce different targets and
therefore different final colours depending on the paper used?
Discuss :)
Thanks
Ken Jones
Technical Production Manager
Penguin Group (UK)
80 Strand, London, WC2R 0RL
Direct Dial +44 (0)20 7010 4136
Bodoni Systems Ltd