QTR-Quadtone RIP

I am sorry if this newbie question seems simple, but I was wondering if when you 
speak of bronzing, I have read other articles/posts that refer to metamerism. 
Are these terms interchangeable or am I wrong to assume that?

Thanks, 

Dennis.

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Metamerism is when colorinks printed on paper  gets colorcasts in different kind of light. Eg. a neutral black print in tungsten light gets a green cast in sunlight or in fluoriscent light.

Bronzing is when the inks get a different sheen or gloss in the highlights and towards the darker parts of an image. Gloss difference. Can look like kinda bronze metal in the sheen.

Better explanations may come from others.

Finn


Den 25. mai 2011 kl. 20.32 skrev Dennis Linden:

> I am sorry if this newbie question seems simple, but I was wondering if when you 
> speak of bronzing, I have read other articles/posts that refer to metamerism. 
> Are these terms interchangeable or am I wrong to assume that?
> 
> Thanks, 
> 
> Dennis.
> 
> [Non-text portions of this message have been removed]
> 
> 



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Dennis Linden <roguemd@...> wrote:

>
>
> I am sorry if this newbie question seems simple, but I was wondering if
> when you
> speak of bronzing, I have read other articles/posts that refer to
> metamerism.
> Are these terms interchangeable or am I wrong to assume that?
>
Bronzing and metamerism, as I think of them, are different.

An example of bronzing is at page one of
http://www.paulroark.com/BW-Info/1100-HpGO.pdf

Metamerism is a problem of colorants that take on slightly different hues as
the light sources vary.  See http://en.wikipedia.org/wiki/Metamerism_(color)

Paul
www.PaulRoark.com


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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 )                 |

Bronzing is also a term held over from the days of darkroom/wet processing.
The silver can leach out onto the emulsion surface under certain
circumstances producing a bronze sheen. Certain other traditional toning
techniques produced a similar effect within the emulsion without degrading
the image. Metamerism wasn't around then.

On Wed, May 25, 2011 at 5:46 PM, Paul Roark <roark.paul@...> wrote:

>
>
> Dennis Linden <roguemd@...> wrote:
>
> >
> >
> > I am sorry if this newbie question seems simple, but I was wondering if
> > when you
> > speak of bronzing, I have read other articles/posts that refer to
> > metamerism.
> > Are these terms interchangeable or am I wrong to assume that?
> >
> Bronzing and metamerism, as I think of them, are different.
>
> An example of bronzing is at page one of
> http://www.paulroark.com/BW-Info/1100-HpGO.pdf
>
> Metamerism is a problem of colorants that take on slightly different hues
> as
> the light sources vary. See http://en.wikipedia.org/wiki/Metamerism_
> (color)
>
> Paul
> www.PaulRoark.com
>
>
> [Non-text portions of this message have been removed]
>
>  
>


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