Datacolor User to User Support Group.

Actually your response leaves me even more confused.

I printed the color and gray targets on the same sheet of 11x17 paper
that was cut in half to 8.5x11. Printed within 5 min of each other and
left to dry down for 24 hours before measuring. The high negative b
values only occurred when measuring over multiple sheets of paper, it
was something like -9 over the black backing sheet. For the final
profile I measured both the color and gray targets over the black
backing sheet. So there should be no difference at all between the
color and gray targets.

As far as the spectros go, do you have different classes of spectros
designed to accommodate extreme levels of OBAs? If so does this limit
the spectro's accuracy when measuring papers with lower levels of OBAs?

Gack! Oh the complexity! This box of paper was $25 less than a box of
Epson Premium Luster, maybe this wasn't a good trade off :-(

Derek 

--- In colorvision_group@yahoogroups.com, CDTobie@... wrote:
>
> 
> In a message dated 11/20/07 1:12:48 PM, dealy663@... writes:
> 
> 
> > I'll clean the tile and re-measure. Have you heard of this type of
> > problem with the IJA Micro Ceramic luster before? I've measured many
> > other RC papers like this and not seen the spectro freak out in such a
> > disastrous way.
> > 
> Papers with huge amounts of artificial brighteners can be tough to
process. 
> Staying away from such papers is a good idea in the first place, but
the only 
> thing we can do if your spectro reads that paper white as bright
cyan, is 
> replace your unit with one that can handle it better...
> > 
> > Also why does the weirdness really only seem to come out when I add
> > the gray measurements?
> > 
> Problems that occur when adding the grays usually are caused by
differences 
> between the color and gray target. Different amount of drydown,
different media 
> setting, or perhaps from your description different spectro response to 
> white, if in one case more whitened paper is under it, and in the
other a dark 
> sheet is under it. This is a yes/no situation. Does paper white read
with a high 
> negative b* value or not. If yes, nothing else matters. If no, then
its a dif
> ferent problem.
> 
> C. David Tobie
> Product Technology Manager
> Digital Imaging & Home Theater
> Datacolor Inc.
> CDTobie@...
> www.datacolor.com/spyder3
> 
> 
> 
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