Dear ColorSync List, Today, I was working on an Epson 7890 printer at a client. According to my automated spectrophotometer, the measurement I got off my client proofing substrate was :
95 0 -2.3 in M0
I know I have a choice of M0/M1/M2 CIE Lab coordinates off this instrument. But in the heat of things (I had all kinds of troubles.?), I did not pay attention to the possible differences between each and stuck with M0. My handheld instrument (tungsten illumination M0 only) gave me :
95 0 -3.5.
A higher negative b* value. I know, it is not a huge difference. In general, does M1 "reduces" fluorescence, much like "M2" UV filtering or does it "increase" its value? In "theory", I would think that M1 makes an optically brightened paper more "b* negative", so that, an M0 instrument, which does not stimulate much UV fluorescence in the 360nm range, would give a b* = -3.5. But what is the "real" story behind M1? Is it to cause the substrate to fluoresce "more", by throwing more UV energy at it? Therefore, causing the b* to be "higher" than -3.5? Like -5.00 or -6.00? Or is it supposed to yield a b* less than -3.5, as in the case of this proofing paper? I confess I have to do additional readings on the subject. (I can be such a newbie at times.) But here is what I do *know* will happen, from experience : if the substrate appears more bluish (higher b* negative value), because of M1 higher UV illumination, therefore, the proof will appear more "yellowish", in Absolute Colorimetry, that has always been my experience, for a Source print process that has a b* closer to zero. But if the substrate appears "less bluish", because of M1 illumination, then the proof will appear less yellowish, in AbsCol. Does that make any sense? I really need to brush up on my understanding of M1. Thank you in advance for your patience and help. Best / Roger www.graxx.ca
Roger, maybe this article clarifies things? https://www5.konicaminolta.eu/en/measuring-instruments/learning-centre/colou... <https://www5.konicaminolta.eu/en/measuring-instruments/learning-centre/colour-measurement/colour/iso13655-demystified.html> Short: M0 = undefined UV. If a fresh tungsten lamp is used in an M0 instrument the OBA is excited nearly like with illuminant CIE A which means that the fluorescence is weaker than with D50 (M1). This leads to more yellowish readings (also a more yellowish appearance in a viewing environment that has the same UV energy as CIE A). But as M0 is undefined a different M0 instrument can theoretically excite the OBA even more than D50 (e.g. the old Avantes Spectrocam). Best regards Claas
Am 12.06.2019 um 23:33 schrieb Roger Breton via colorsync-users <colorsync-users@lists.apple.com>:
Dear ColorSync List,
Today, I was working on an Epson 7890 printer at a client.
According to my automated spectrophotometer, the measurement I got off my client proofing substrate was :
95 0 -2.3 in M0
I know I have a choice of M0/M1/M2 CIE Lab coordinates off this instrument. But in the heat of things (I had all kinds of troubles.?), I did not pay attention to the possible differences between each and stuck with M0.
My handheld instrument (tungsten illumination M0 only) gave me :
95 0 -3.5.
A higher negative b* value. I know, it is not a huge difference.
In general, does M1 "reduces" fluorescence, much like "M2" UV filtering or does it "increase" its value?
In "theory", I would think that M1 makes an optically brightened paper more "b* negative", so that, an M0 instrument, which does not stimulate much UV fluorescence in the 360nm range, would give a b* = -3.5.
But what is the "real" story behind M1? Is it to cause the substrate to fluoresce "more", by throwing more UV energy at it? Therefore, causing the b* to be "higher" than -3.5? Like -5.00 or -6.00?
Or is it supposed to yield a b* less than -3.5, as in the case of this proofing paper?
I confess I have to do additional readings on the subject.
(I can be such a newbie at times.)
But here is what I do *know* will happen, from experience : if the substrate appears more bluish (higher b* negative value), because of M1 higher UV illumination, therefore, the proof will appear more "yellowish", in Absolute Colorimetry, that has always been my experience, for a Source print process that has a b* closer to zero.
But if the substrate appears "less bluish", because of M1 illumination, then the proof will appear less yellowish, in AbsCol.
Does that make any sense?
I really need to brush up on my understanding of M1.
Thank you in advance for your patience and help.
Best / Roger
www.graxx.ca
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participants (3)
-
Claas Bickeböller
-
Graeme Gill
-
graxx＠videotron.ca