Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Ernst Dinkla <edinkla@...> wrote:

> 
> In 2001? Wilhelm gave Fuji Crystal 60 years, later on 2004?  that
> dropped to 40 years.
> You will see shops give either the old or new numbers depending on their
> interests.

Yes, I believe the change reflects the inclusion of fade data for 0.6 density level patches in addition to the previous testing that used only 1.0 density level patches (i.e., the adoption of the newer WIR endpoint criteria set v3.0) .  If you look at the AaI&A test results carefully you will notice that the highlight colors are more affected by fade than the midtones and shadows. Hence, weighting the test results with additional lower density patches will produce a drop in test score which is what happened (ie. 35% density loss occurs more quickly in the 0.6 patches than the 1.0 patches). In other words, considering fade as a change in the photographic tone curve,  the tone curve shifts parallel to its original position for the most part which "pushes" the color reproduction down the curve, and the lightest colors start to clip as they get compressed towards media white point.  Inkjet prints don't respond in fading tests with this very predictable "parallel shift" in the curve like chromogenic color papers  because the color blends aren't  formed by just three stacked layers of isolated dyes (cyan, magenta, and yellow, no black) as they are in chromogenic color prints.

 
> Image Engineering has it at 17 years,
> More than 100 at the ozone test (like more RC based prints),
> http://www.image-engineering.de/index.php?option=com_content&view=article&id=57&Itemid=91

Yes, the IE and WIR use similar densitometric endpoint criteria, but IE uses a more UV-blue wavelength rich light source than WIR which uses cool white.  Crystal Archive paper incorporates effective UV blockers in a supercoat gelatin layer, so extra UV in the light source doesn't have a pronounced effect on the fade rate of Crystal Archive. it's the extra blue wavelength energy that is the primary reason for IE's lower score than WIR.  AaI&A uses full spectrum/high CRI FL lamps rather than cool white FL, so again, more blue wavelength energy than WIR in the test, and thus closer agreement to IE test scores than WIR.

One other point -there is no right or wrong choice, IMHO, for light sources to use in accelerated light fade tests. Many photographs are indeed being lit primarily  by cool white fluorescent (increasingly common as homes move away from incandescent to FL lamps), others by natural daylight, others by tungsten or halogen, soon LED.  Which spectrum induces the most fading? Well, technically speaking,  glass-filtered Xenon light sources  reproduce theUV/VIW content natural daylight better than others, therefore is arguably the most potent choice for a light fade test. However, IMHO, the light you are using to light you prints is the source that is most damaging!. And many prints are framed nowadays with UV filtering glazing (even standard acrylic significantly filters UV), so an answer derived from rich UV content in test is not always the more appropriate answer.   AaI&A's choice of full spectrum FL strikes a kind of middle ground that reasonably simulates natural daylight but with some filtering of the UV content, and it is a defensible choice as are the sources used by the other labs.  AaI&A went with 5000K 93CRI FSFL to  achieve that extra blue needed to induce most of the fading (and good color discrimination ;-)), but also for economic and environmental reasons. The AaI&A tests are very energy efficient.  Al Gore would approve!

cheers,

Mark

> For Aardenburg I think the patch number will have an influence. Intended
> to give a true rating for printers that replace color mixes with sigle
> hue and monochrome dots it may as well be more severe on coupled dyes in
> continuous layers = chromogenic prints. Check on what colors fail in
> the tests, If they fall outside the Wilhelm patches you have an answer.
> Didn't check that so I could be wrong.
> 
> -- 
> Met vriendelijke groeten,   Ernst
> 
> 
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