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Thread: Jon Cone on Carbon Piezography

  1. #31

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    Re: Jon Cone on Carbon Piezography

    Quote Originally Posted by Ken Lee View Post

    I see that in rough terms, the range goes from roughly 1 to 150, with the highest rating given to the HP Designjet Z3100 24" + Crane Museo Rag paper: 152 Megalux. Left in the "south-facing window", such prints would exhibit little fading until after (152/100 * 2.3) = 3.5 years.
    Yes, direct sun is a harsh mistress for any artwork. Even pure cotton papers and photographic grade gelatin binders will degrade within a decade or so under the "front facing window" scenario, so that even if the image is formed with a noble metal like Pt or Pd the organic support layers will ultimately let the system down before the image forming components fade.

    Quote Originally Posted by Ken Lee View Post
    What does it mean that the rating for Epson Stylus Pro 9800 with Cone Piezotone™ (Carbon Sepia with Portfolio Black) inks on Hahnemuhle Photo Rag paper, has a CDR of "9-140" ? What does the 9 designate ? Most of the ranges we see in the test results are closer: 65-87, 80-88, etc.
    The sample you are referring was made with Portfolio black ink. Jon Cone has offered two matte black ink formulations over the years, one he calls "museum black" and one he calls "Portfolio black". Portfolio black gives somewhat richer dmax but Jon freely admits it's not as stable as museum black. The current CDR of "9-140+" means the lower CDR limit triggered very early in test at just 9 megalux hours due to changes occurring in the worst 10% of patches, ie. primarily in target patches E5, F4, and F5 (take a look at the table data for those patches in the reports). These are essentially the only patches where the Portfolio black ink was being feathered into the mix. F5 is the dmax patch, and dmax areas often have an excess of ink so there's some "sacrificial" protection to the dmax patch density due to this excess ink. Yet this patch has still changed somewhat, but in patches E5 and F4 the Portfolio black was being "feathered" into the mix by the printer RIP at a much lower level and it faded rather quickly, leaving behind the warmer carbon particles which give these patches the majority of their color and tone. Thus, those patches shifted a little in hue towards a more sepia appearance in less than 10 megalux hours exposure. That's what triggered the lower CDR rating of 9 megalux hours. As the tests proceeded some additional fading in those patches has continued whereas all other patches are highly stable due to the full carbon content. Because the highlight, midtone, and shadow image tones are comprized solely of the pure carbon pigment (i.e, no portfolio black mixed in) they are on average quite stable, and this is the reason why the upper CDR limit still hasn't triggered. Note: When you see a "+" sign in the CDR column it means the upper limit still hasn't been triggered (e.g., in this sample the test has now gone 140 megalux hours and the upper CDR limit will eventually be at least that good but probably better). This sample and two others using the Portfolio black ink are rather unique examples of inkjet craft. It's really what the AaI&A Printmakers' Testing fund is all about - giving artists a chance to collaborate with AaI&A and submit examples of craft that would likely never get tested otherwise.. in other words, these are real world results for what dedicated printmakers are doing with inkjet technologies these days.


    Quote Originally Posted by Ken Lee View Post
    Members can view the detailed reports, and compare original versus exposed color patches (Man, are you ever thorough!). Looking at the test of the above-mentioned HP printer after 180 Megalux hours, it's remarkable how little difference there is to the naked eye. On the other hand, doing the same for the Piezotone test, differences are apparent at lower numbers. Is that because it is easier for the eye to discern fading of patches in monochrome than in a wide range of colors ?
    You got that exactly right, and it's a significant reason why I invented the I* metric. I concluded that traditional densitometry and color difference equations were inadequate to evaluate visual changes occurring in photographs, either due to aging over time, or even when, say, one compares a copy image to an original image for tone reproduction quality. Traditional color difference models (delta E, delta E 2000,etc) evaluate two side-by side colors merely for colors' sake. They are thus an excellent metric for process control, but in paintings, drawings, and photographs we see a complex assortment of colors and tones that form contextual meaning. The human brain interprets this context (e.g., pattern recognition, scene color balance, etc) and in doing so relies on the low chroma colors (i.e. neutrals and near neutrals) as a kind of baseline for evaluating the color appearance of the scene lighting, ie. how cool or warm the light of the scene is when judging the color and tones in that scene. We also detect the visual contrast of neighboring image areas which is what pattern recognition is all about, so I* tone calculates the L* gamma for near-neighbor tones in order to determine changes in both lightness and contrast whereas I* color tracks changes to hue and chroma accuracy. Color difference models lump lightness, hue, and chroma together, so the important role of image contrast in retention of overall image quality does not get evaluated properly.

    If you'd like to see a good visual example of color in context versus color purely for colors' sake, take a look at the article "An Introduction to the I* metric" on the documents page of the AaI&A website. The direct link to the article is:

    http://www.aardenburg-imaging.com/cg...U2Nzg5LyoxMQ==


    cheers,
    Mark
    http://www.aardenburg-imaging.com

  2. #32
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    Re: Jon Cone on Carbon Piezography

    Wow

    Quote Originally Posted by MHMG View Post
    Traditional color difference models...are thus an excellent metric for process control, but in paintings, drawings, and photographs we see a complex assortment of colors and tones that form contextual meaning. The human brain... relies on the low chroma colors (i.e. neutrals and near neutrals) as a kind of baseline for evaluating the color appearance of the scene lighting,
    It will take a while to absorb the entire article, but the photos you show on page 13 illustrate your point quite dramatically... and remind me why I work in monochrome

  3. #33

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    Re: Jon Cone on Carbon Piezography

    Quote Originally Posted by Ken Lee View Post
    Wow



    It will take a while to absorb the entire article, but the photos you show on page 13 illustrate your point quite dramatically... and remind me why I work in monochrome
    Ken,

    Yes, I didn't take the time to go back through the article and cite the appropriate page, but you have indeed found it. You clearly have a good handle on what these concepts are all about. I hope it sheds some light (pardon the pun) on why single value print longevity numbers are for the most part grossly oversimplified assessments of overall system light fade performance. Almost any print can easily "last" over 100 years if one chooses benign display environments and allows for moderate to high changes in visual appearance of the print over time. That reality doesn't negate the fact that some systems are far more stable than others and will tolerate excursions into not-so-benign environmental conditions for longer periods of time while still retaining good to excellent visual and physical properties.

    best,
    mark

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