I believe Graeme is eluding to the fact that color temperature does not speak to speak distribution; so while D50 is a standard with a specific distribution and as such has a color temperature, one cannot make the inference (as it seems the language on the pantone has done) that because the temperature is 5000K the spectral distribution has any specific character.  These test strips are useful to show clients when the lights in their office are inadequate for proofing purposes and can accomplish that task quite nicely. Most people do not understand that there is a difference but the seeming magic of these strips can quickly open the eyes of most clients as to why we insist on a light booth with a standardized light source for contact proofing. Cheers Daniel Perfect logic is meaningless without perfect perspective. Daniel Westcott daniel@westcott.us -------- Original message -------- From: Claas Bickeböller <lists@bickeboeller.name> Date: 11/18/2013 8:27 AM (GMT-07:00) To: ColorSync <colorsync-users@lists.apple.com> Subject: Re: Light indicator band issues. 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

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