Don Stauffer in Minneapolis wrote:
Nicholas O. Lindan wrote:

"Jerry Avins" wrote


I recall that the contrast between printer's ink and glossy paper is
about 10:1 and B&W prints on glossy paper are a bit better (but on


Correction: 30:1.



Photographic paper can get to 2.0 od reflected, a range of 10 ^ 2 =
100:1.

I just took a measurement from a printed page on coated stock, it
yielded 1.27 = 1.3 = 10 ^ 1.3 = 20:1.

Unless print paper has changed in the twenty-five years since I made
some of those measurements, paper doesn't quite get to 100:1. I have
seen papers with blacks at 2% (50:1). Most papers have about 3% black
reflectance, however (33:1)

At one time I worked on a project finding black coatings for cameras and
other EO sensors. It is amazing how hard it is to get a truly black
black. Even the famed 3M Black Velvet was a 2% reflectance. The only
thing we found was a coating by Martin Marietta that was close to 1%.

The emulsion itself in photographic paper is what creates that
reflection, regardless of how much black silver it has in the emulsion.
I would assume in inkjet ink it would be the binder that holds the
pigment or dye to the paper. With laser printers the toner has some wax
in it.

I once got down to about 0.2% edge-on to a stack of single-edge razor
blades with the backs removed. (I was puzzled at first by poor
performance, but it worked like a charm after being degreased.) That's
about what one gets with a Tyndall tube*. I still have a can of 3M's
Nextel Velvet Black, but as far as I know, they don't make it any more.
(Nextel now means something else.) Kodak's Brushing Lacquer was pretty
good, too, but I think that's also a thing of the past. I'm almost out
of Edmund's flock paper, but that's still available.

Jerry
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* I found no web reference to a Tyndall tube, so I figure a brief
description is in order. Tyndall needed a good light absorber for his
ultramiscrope, http://tinyurl.com/66e63 He drew a piece of glass tubing
-- a side tube on his specimen chamber -- to a cone that curved like the
toe of a jester's shoe. The outside of the tube was coated in soot from
a candle flame. Light entering the tube is reflected deeper and deeper
into the small end, suffering a small loss at each reflection.
Eventually, a ray turns around and starts out, again reflecting many
times. By the time it emerges, all those slight absorptions have pretty
well attritted it to zilch.
--
Engineering is the art of making what you want from things you can get.
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