Digital BW, The Print

> -----Original Message-----
> From: hogarth [mailto:hogarth@...] 
> Sent: Saturday, December 13, 2003 10:51 AM
> To: digitalblackandwhitetheprint@yahoogroups.com
> Subject: Re: [Digital BW] barrier-paper Dmax, (was: Semi 
> matte, PremierArtPrint Shield...)
> 
> Paul? Anyone? How does a barrier-type paper effect Dmax?
> 
Hogarth,

RC or barrier papers simply provide a smoother surface to print on. The
smoother or glosser the surface the greater the Dmax will be. Reflective
density is measured by shining a light of known strength on a surface and
then measuring what percentage of the light is reflected. The angle of
incidence between the light striking the paper and the light reflected from
the paper is 2 or 4 degrees. Very close to what you see if you look straight
at the paper.

Matte surfaces scatter the light being reflected from their surface
resulting a greater amount of light returning to your eye and lowering the
Dmax. Glossy surfaces have little scatter to adversely effect Dmax.

You can really see this by applying a glossy coating to an inkjet print on
matte paper. Prior to coating the Dmax will be in the 1.6 to 1.7 range and
after coating it moves up into the 1.9 - 2.1 range without any other change
taking place accept a smoothing of the reflecting surface.

Density differences become harder and harder to see as you go above 2.0.
Keep in mind that a density of 2.0 means that 1.00% of the light falling on
the surface is reflected. At a density of 2.1 the reflectance is 0.79% a
very small change. At density 2.2 reflectance is 0.63% an even smaller
change.

So as density increases the increase in visible "darkness" becomes less and
less. I can personally distinguish between a densities of 2.0 and 2.1 but
from 2.1 up my eyes are not up to seeing the change. Dmax values above 2.1
seem to have little or no practical value.

On matte papers with carbon pigment inks the best Dmax values seem to be in
the 1.6 to 1.7 range. This would be a reflectance of 2.51% to 2.00%.
Differences in this density range are easily seen.

Martin Wesley
www.carolynfrayn.com/Guests/MartinWesley/pages/MW_01.html
www.borderless-photos.de/guests.html