Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla <edinkla@...> wrote:

> To get some references I checked the paper white measurements in the 
> Aardenburg test results:
> 
> William Turner 310 gsm with UV included:
> Lab 95.9 0.2 2.3
> 
> I guess that it is measured on a black tablet, my results are:
> 
> 310 gsm
> Lab 95.27 0.42 2.55 on a black tablet
> Lab 95.69 0.68 3.06 on a stack of William Turner

HI Everyone,

Actually I make all media white and max printed black readings for the Aardenburg test reports on the table-white surface of my Gretag/Macbeth Spectrocan. As you can see in Ernst's measurements a black backing will often give slightly lower L value than a white backing due to less secondary light scatter coming back through the media, but I believe most prints are framed on white or near white matting and mount board, so a standardized white backing is more appropriate to what one is going to observe more often in practice.  Other color scientists recommend standardization on a black backing because these readings would tend to include opacity of the substrate which is also a legitimate media property to be concerned about. Ideal answer would be to measure both, but I had to draw the line somewhere. I'm generating tons of data as it is already!

BTW, I do have one sample of Canson Infinity Rag Photographique in test. Submitted by an AaI&A member from Australia, I measured paper white point as:

UV included - 97.6, 0.4, 0.9
UV excluded - 97.8,0.4, 1.0

With a delta b* value of only 0.1 (effectively within instrumental error) this paper clearly has no OBA present whatsoever. HPR has some OBA in paper core.  The commendably high L* value and the near neutral a* and b* values are impressive. Max printed black was a little higher than I'm used to seeing with Epson MK inks, coming it at 19.4 for a color print sample made on an Epson 7900 with HDR ink set, whereas HPR typically measures about 17. However, the L* range from media white to printed black is essentially the same. Most viewers will respond favorably to the brighter white point, again a very impressive achievement considering it's getting no "boost" from OBAs.

cheers,

Mark
http://www.aardenburg-imaging.com