QTR-Quadtone RIP

Gloss difference happens at the top layer of the print and the term 
describes it quite adequate. One way or another different colors or 
different grey values do not get the same gloss on the surface. In more 
than one angle of reflectance. An almost normal gloss difference happens 
in white areas with no ink at all if compared to the other spots. Some 
printers can add an ink medium varnish there too to overcome that.  A 
matte pigment black will result in a heavy gloss difference in the 
blacks and shadows if used on a glossy paper. So there is a photo black 
pigment ink for gloss papers: lower quantity of pigment and smaller 
pigment particles. Dye inks still offer the best overall gloss in practice.

While I first thought that bronzing had to do with pigments more or less 
staying on top of the inkjet coating I now think it has to do with the 
ink layer thickness and a kind of interference in the reflected light. 
The color changes with the angle of reflection. Gloss difference does 
not have to occur. By varying the ink limits the bronzing usually shifts 
per greyscale patch but does not disappear. Varnishes or gloss enhancers 
can sometimes reduce the effect but not always and I guess it must be 
related to the optical properties of the resins used. Ink medium and 
gloss paper coating can match with little bronzing while another inkset 
can be quite bad on the same paper.

When two different color patches match in the same light and to one 
observer (sensor, eye, etc) it is called a metameric match. When they do 
not match to another observer and/or to another light it is called a 
metameric failure. In practice the last is often described as 
"metamerism" but when it is used for only one color sample or one color 
print that gives unexpected color shifts between different light sources 
it should be called "illuminance color inconstancy". The ink colorants 
themselves can be the cause but more factors can play a role: 
fluorescents in the paper coating for example.

-- 
Met vriendelijke groeten,   Ernst

Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/

|      Dinkla Grafische Techniek      |
|         www.pigment-print.com        |
|                 ( unvollendet )                 |