Manual, explication and more.
Intro
Running a small print shop with several inkjet printers and a variety of papers
and other media, one likes to know every detail of the process. That was the
main reason to create this set of paper white spectral measurements. I’m not the
first to do it and it isn’t the only place on the web where you can get that
information but I try to deliver more content than what has been available so far.
I like to thank my son Kasper Dinkla for the visualisation of the measurements,
for which he applied an existing open source tool; JFreeChart.
Manual
The application SpectrumViz.jar is a Java based tool.
On most computer systems today the necessary
environment to let it run will be available. If not,
download the suitable Java Runtime Environment and
install it. JRE download Oracle/Sun
The application is in a jar type format which makes it
instantly ready for use while the content is
sufficiently compressed for download, so no
decompression is needed or should be done.
When the application is started there will be some
spectral plots visible in the main window right away.
One is of Barium Sulphate BaSO4, another Titanium
DiOxyde TiO2. In this case used to give some
reference for the other measurements to known ‘ideal
but existing’ white surfaces. Both components are
used as whitening agents in paper coatings. Another
spectral plot represents an Optical Brightening Agent,
OBA or sometimes called Fluorescent Whitening
Agent or Fluorescent Brightening Agent that I prefer.
The plots will disappear as soon as other maps or
media choices in the maps are ticked. A CTRL +
mouse click on other maps and media choices will
keep the default curves and add extra curves. A CTRL
+ mouse click on an already selected choice will only
deselect that choice. A mouse right click if possible
will have similar functions as a CTRL + left click. A
Shift + mouse click visualises a range of media
choices. With the arrow/cursor on a media name, the
weight in Grams per Square Meter and the Lab color
of the paper’s print side is displayed. Other relevant
paper properties will be added there later on. A right
click on the curves window will give some menu
choices for display changes like zooming in and out
with different aspect ratios or fixed, save curve
visualisations as png images, copy and print facility,
etc. Dutch language but it will explain itself.
Selecting parts of the curve on the window itself is
possible too
Purpose
While it may have been curiosity that fueled my
desire to create this information tool, there could be
hidden benefits for its users. For the print shops that
are interested in the archival qualities of the paper
white, the curves will show whether there are
Fluorescent Brightening Agents (FBA) used in the
paper and where in its structure, coating or base. Fluorescence can create color
inconstancy under different lights. The effect often incorrectly called
“Metamerism”. There can be more causes for that effect though. In absence of
FBAs, the total reflection and the straightness of the curves tell something about
the quality of the normal whiteners used in the inkjet coating and of the paper
base reflectance quality. For the book producers the three curves of each paper
tell something about the papers opacity/transparency, based on the GSM weight
or other properties that influence opacity. The two curves of measurements on
black board also tell something about reflectance differences of dual sided
papers. The three curves per paper are a good indicator whether papers with
different names and from different suppliers may come from the same source. If
so that could help on applying suitable ICC print profiles for papers that do not
have a profile available, make a selection of a set of matching white papers
easier and last but not least gives an advantage in the purchase of the ‘same’
paper from different suppliers. Spectral measurements do not tell all about the
paper and its coating but they shouldn’t be underestimated either.
Basics
For the spectral measurements a new X-Rite Eye One Basic is used, in this case
the version that doesn’t have a UV cut filter as I was interested in the
fluorescence behaviour of the papers. The software used is X-Rite (Gretag
Macbeth) Eye One Share. Three spectral measurements per media were done,
one on the print side of the paper with a natural (no FBAs) white museum
mounting board underneath the paper to represent a print as mounted (solid line
curve), the second a measurement on the same side but the paper resting on a
black plastic board (dashed line curve), the third measurement on the backside
of the paper and the paper resting on a black plastic board (stipple line curve).
The Lab value is derived from the first measurement. Illumination D50,
Observer 2°.
In the Miscellaneous map the Pressed PTFE Tile spectral plot was reconstructed
from a research article graphic and the three measurements on one Teflon Roll
were done by me with the Eye One Basic. The PTFE-Teflon choices are a bit
out of context here but another idea still not really explored may bring the
relation later on.
Interpretation of the spectral plots
If we start with the Pressed PTFE Powder (red solid line) we see what comes
close to an ideal white reflectance surface. A reflectivity just below 100% over a
long range of the spectrum, only a part of that is shown here: 380 to 730 Nm.
The opal like structure of Teflon gives it that high reflectance. There are no
peaks or valleys in the line so it is an ideal continuous spectral white. The line is
slightly inclined so not an absolute neutral white but most likely the best neutral
white you will find on this planet. Just a (not visible) bit warmer than absolute
neutral with the 99.04 percentage value at 730Nm and 98.37 at 380Nm. The
BaSO4 sample (brown solid line, covered by the red line) is slightly warmer. No
wonder both are used to calibrate optical instruments on in labs. The Teflon Roll
is not visible here, it is the poor man’s equivalent of a Pressed PTFE Powder
tile.
The green and yellow curves represent respectively Canson Rag Photographique
310 gsm and Moab Entrada Rag Natural 330 gsm dual sided. Two quality matt
photo/art papers with a high reflectivity for that kind of papers. They are almost
identical but show some interesting small differences. The dual sided coated
Entrada should have identical measurements on the two surfaces with black
underneath, it comes close to that if you look at the yellow dash and stipple
curve. The Photographique’s green curves separate there slightly more. The
Epson Enhanced Matte represented by the blue curves shows a huge difference
between printable side and the back of the paper. It doesn’t belong in that class
and it shows.
Opacity is best checked at the right end of the curves, the wider the gap between
the solid and dashed curve (same printable side measured respectively with
white museum board and black plastic board underneath) the higher the
transparency, the lower the opacity of the paper. In this case the Entrada shows
more opacity despite its slightly lower weight, 300 versus 310 gsm. Most likely
the extra coating side of the Entrada adds to the opacity. The Epson Enhanced
shows a much wider gap which will be partly caused by its lower weight of 190
gsm but could as well be the result of an inferior coating that relies more on
FBA content for the print side reflectance than on good quality normal
whiteners and a quality paper base.
FBA content is very visible in the Epson Enhanced, the UV light, left of 420Nm,
is absorbed by the agents so doesn’t show reflectance there and converted to
visible light, blue mainly, by the agents it shows in the form of a bulge at the
other side of 420 Nm. With only the printable side showing that behaviour (solid
and dashed curve) it is clear that the FBA content is in the coating itself, the
paper base doesn’t have it. Most papers in the list that contain FBA have it both
in paper and coating, in some cases more in the paper than in the coating. There
are reasons to expect a better fade resistance of the FBAs when applied in the
paper than in the coating but much depends on other qualities too. In general
FBAs are not fade resistant and should be avoided for prints that have to last
The Epson Enhanced’s print side is cooler in color than the two other papers but
its back warmer and less bright given enough UV light in the illumination of the
paper.
Three Resin Coated papers, like most RC papers with a heavy FBA content. The
blue Moab Lasal Photo Matte dual sided is equally bright on both sides, in this
case hard to say whether the paper base contains less FBA. The green FujiFilm
Photo Glossy RC most likely has the brighter printing side due to a higher FBA
content in the coating and not because it is glossy. The yellow FujiFilm Satin
shows a high FBA content in its paper base and less in its coating. With the FBA
in the paper base contained between the polyethylene (RC) barriers it may last
longer, less affected by gas fading.
The spectrum plots can help in selecting more durable papers, but real fade and
color shifting results of papers are better collected from fade testing. The
Aardenburg Imaging & Archives founded by Mark McCormick-Goodhart is the
best place to check fading of prints including paper white color shifts. Any
serious print shop should become a member of that initiative and get full access
to all the data collected. Aardenburg Imaging & Archives
Five sets of measurements of Fibre-Baryta papers, the odd one out is the
FujiFilm Museum Baryte. The remaining four; Hahnemühle Photorag Baryta,
Lumijet Natural Pearl, HP Baryte Satin, Sihl 4804 Professional Photo Barite
have a lot in common.
Not to spoil your appetite for SpectrumViz itself, the explanation ends here.
More than 300 papers measured already, come back for new additions.
Copyright on text, illustrations and measurements: Ernst Dinkla
Do you have comments,
advice, a critical note,
suggestions for
SpectrumViz and this
page? Send them to
Any inkjet paper
manufacturer or
distributor interested in
having its papers
included in the list, can
send samples to me,
preferably several A3 or
A4 sized sheets per
quality. I need more
sheets for some print
tests later on, the
results will be added to
