[Openicc] meta data in test chart

[Chris Murphy]

On Jan 21, 2011, at 7:06 PM, Robert Krawitz wrote:
> 
> Have you found that paper changes over time -- e. g. is Premium Glossy
> now the same as Premium Glossy from 5 years ago?  And are all sheet
> sizes the same, or do you find differences there?

I have found they change over time with the contracts companies have with paper mills, and various coatings improvements. But then we also get changes in the names of media when no physical change in the media has occurred. So it's tough to track this.

As far as I am aware, if there is a difference between roll and cut sheet, rolls of various sizes are coming from the same master rolls, and cut sheet of various sizes are coming from the same master supply. So there's a reasonable assurance that all rolls are the same; and all cut sheets are the same.

One exception to that: There is evidence to the contrary in some of the pro printer drivers where there is a separate listing for Luster 250 and Luster 260, meaning two different rolls of luster paper that differ in gsm. However, I have it on reasonably good authority that the weights aren't actually any different, it's just used to keep the products separate because they're made from different manufacturers (or at least coated by different finishing companies). And then there's a Luster 255 which is cut sheet and that's different yet again.

> 
> Another thing here -- there might be multiple recipes that come close,
> but aren't identical.  So for imperfect matches, how do we determine
> (or help the user find) a best fit?

At the moment it probably can't be done automagically. There are (or were) some HP printers that had some sort of bar coding on the back of every sheet and the printer and driver would talk to each other to make sure the driver was populated by default with the correct media type. But all of this depends on sufficient granularity for media types in the driver, and bar coding them differently at different manufacturers. There's no standard for this. Would be nice.

But the manufacture of ink and paper is always subject to variation. So at any time we can get a change in behavior, and it's usually not predictable. You put the paper in, make a reference print - oh how about that! Time to reprofile! That's about the best case scenario.


Chris Murphy