Dear all, I experience some problems with different light indicators like : PANTONE® LIGHTING INDICATOR Stickers PIA/GATF RHEM Light Indicator Ugra/Fogra light indicator Each one appears slightly different under the same light. E.g. with a colorCommunicator and fluorescent tubes 5000 K. Has anybody already seen this issue before? Is it possible to obtain non uniform results? Could I trust them to put them on the digital proof prints? Many thanks beforehand for your explanations sincerely, Axel Robert | UBISOFT Tel. : +33 (0)1 48 18 52 03 | Port. : +33 (0)6 68 83 34 67 | Skype: axelprepress ”It is important that you know where you come from, because if you do not know where you come from, then you don’t know where you are, and if you don’t know where you are, then you don’t know where you’re going. And if you don’t know where you’re going, you’re probably going wrong .”
Axel Robert wrote:
Dear all,
I experience some problems with different light indicators like :
PANTONE® LIGHTING INDICATOR Stickers
PIA/GATF RHEM Light Indicator
Ugra/Fogra light indicator
Those indicators seem incredibly vague in what they are supposed to do, and under what conditions they "work". The Pantone indicator talks about "being viewed under a 5000K (degrees Kelvin) standard light source.", and the others use similar terminology, but this is nonsense - such indicators depend on the colors being visual metamers under a certain light _spectrum_. Merely being the right color temperature is not sufficient to guarantee a match. Graeme Gill.
Graeme, You are teasing us. Please elaborate. I had the same 'ambitions' as Axel but only mirrored his disappointment. What exactly is 'sufficient' to achieve a match with a metameric pair? If these things are so inadequate why does UGRA/FOGRA/GATF market them? Mark On 18/11/2013, at 11:32 PM, Graeme Gill <graeme2@argyllcms.com> wrote:
Axel Robert wrote:
Dear all,
I experience some problems with different light indicators like :
PANTONE® LIGHTING INDICATOR Stickers
PIA/GATF RHEM Light Indicator
Ugra/Fogra light indicator
Those indicators seem incredibly vague in what they are supposed to do, and under what conditions they "work".
The Pantone indicator talks about "being viewed under a 5000K (degrees Kelvin) standard light source.", and the others use similar terminology, but this is nonsense - such indicators depend on the colors being visual metamers under a certain light _spectrum_. Merely being the right color temperature is not sufficient to guarantee a match.
Graeme Gill.
Mark
This email sent to mark.stegman@gmail.com
Dear all, these indicators are good tools to warn you if you are in non D50 light. They are not suitable to determine if you have a good D50 simulator. If you do not see or only barely visible differences it _could_ be that you have a good D50 simulation. If you see big differences between the metameric pairs you definitely do not have a suitable D50 simulation. The second application is what these strips are meant for, the first not. Best regards Claas Am 18.11.2013 um 14:04 schrieb Mark Stegman <mark.stegman@gmail.com>:
Graeme,
You are teasing us. Please elaborate. I had the same 'ambitions' as Axel but only mirrored his disappointment.
What exactly is 'sufficient' to achieve a match with a metameric pair?
If these things are so inadequate why does UGRA/FOGRA/GATF market them?
Mark
On 18/11/2013, at 11:32 PM, Graeme Gill <graeme2@argyllcms.com> wrote:
Axel Robert wrote:
Dear all,
I experience some problems with different light indicators like :
PANTONE® LIGHTING INDICATOR Stickers
PIA/GATF RHEM Light Indicator
Ugra/Fogra light indicator
Those indicators seem incredibly vague in what they are supposed to do, and under what conditions they "work".
The Pantone indicator talks about "being viewed under a 5000K (degrees Kelvin) standard light source.", and the others use similar terminology, but this is nonsense - such indicators depend on the colors being visual metamers under a certain light _spectrum_. Merely being the right color temperature is not sufficient to guarantee a match.
Graeme Gill.
Mark
This email sent to mark.stegman@gmail.com
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Mark Stegman wrote:
You are teasing us. Please elaborate. I had the same 'ambitions' as Axel but only mirrored his disappointment.
Hi, sorry, this is the most basic of basic color science. Tri-stimulus matching depends on metamarism. Two colors are assumed to match if the spectrum reaching our eyes triggers the same response in our retina. Our eye's spectral response is modelled by the standard observer matching curves. A painted surface will reflect a spectrum that is the product of the illuminant spectrum and the reflectance spectrum of the paint. So the two paint colors on the test strip will only perfectly match if the illuminant spectrum times the paint spectrum returns a metameric pair - two spectra that trigger the same response in our retina. None of the test patches seemed to specify what spectrum they are expected to match under. A color temperature certainly isn't a spectrum. Now it's possible the test patches were setup to match under "typical" viewing booth illuminant, but who knows, they aren't saying what that is. There is also a limitation imposed by what ink formulations are available/practical. Even if it was intended to match exactly under your particular lamp, it may be too technically difficult to formulate an ink pair that will do so perfectly.
What exactly is 'sufficient' to achieve a match with a metameric pair?
The usual - 1 delta E ! [In practice there is a whole family of illuminant spectra that will give a metameric match. The interesting question is how similar that family is to standard D50 viewing illuminants! ]
If these things are so inadequate why does UGRA/FOGRA/GATF market them?
I'm sure they have a purpose, but they are being rather sloppy in the specifications, and misleading in when they can be expected to "work". Graeme Gill.
participants (4)
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Axel Robert
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Claas Bickeböller
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Graeme Gill
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Mark Stegman