Sammendrag
Different printing systems can produce colours that are perceived as identical under one standard illuminant such as
D50. The visual match will however fail in other illuminations if the spectral properties of the inks differs. For soft
proofing, this requires the proof to be visualised in the defined illuminant. Using more proofing inks than the conventional
CMYK such as RGB increases the colorimetric redundancy, that is the number of different ink combinations
that produce a visual match in D50. Using a spectral workflow, the ink separation can be optimised to get a
visual match in different illuminations. We test here the feasibility of multi-illuminant (spectral) hard proofing with a
multi-channel inkjet printer. We compute the proof of a set of 1269 Munsell patches with an inkjet printer model and
compare the performance of a colorimetric and spectral workflow in terms of multi-illuminant proof matches. We
show that large colour differences in different illuminants can occur when using a colorimetric workflow only optimising
ink separation for D50. Performing a spectral gamut mapping leads to significant improvements as no Munsell
targets show a ΔE2000 larger than 3 for all the illuminations tested. The use of additional red, green and blue inks further
increases the colorimetric accuracy in different illuminations. Spectral proofing with multichannel inkjet printers
opens thus for producing proofs that can be evaluated different visual environments. This can be particularly useful
for packagings that make use of several spot colours and are viewed in very different visual environments.
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