Re: Phosphors
Re: Phosphors
- Subject: Re: Phosphors
- From: José Ángel Bueno García <email@hidden>
- Date: Sat, 16 Aug 2014 21:21:51 +0100
One more for the world:
http://www.bhphotovideo.com/c/product/967078-REG/rotolight_rl_spectra_spectrascope_with_leather_case.html
2014-08-16 20:36 GMT+01:00 Ben Goren <email@hidden>:
>
> On Aug 10, 2014, at 11:24 AM, Robin Myers <email@hidden> wrote:
>
> > Thanks for the link to the NIST site. That saves some work looking up
> emission lines in my old copy of the CRC Handbook of Chemistry and Physics.
>
> My pleasure!
>
> Don't overlook the option to generate vector-based line identification
> plots, which you can easily plop as smart objects in Photoshop on top of
> sample spectra. The tabular data would lend itself well to photorealistic
> recreations of spectra, if anybody was interested in such.
>
> > If someone is not very mechanically inclined, I recommend a cheap
> spectroscope such as the Hand-Held Spectroscope ($10.95) or Pocket
> Spectroscope ($52.95) on the Educational Innovations (
> http://educationalinnovations.com). From Edmund Scientifics there is the
> Spectroscope ($1.95) (http://www.scientificsonline.com/spectroscope.html)
> or the Desktop Spectronomy Kit ($49.95) (
> http://www.scientificsonline.com/desktop-spectronomy-kit.html). I have
> found such devices useful for some color seminars.
>
> Good options. I'd only note that the technical skills to create a
> spectroscope are well within the arts-and-crafts abilities of
> schoolchildren -- but, of course, not everybody has an interest in futzing
> around with scissors and glue. Plus, an handmade spectroscope is unlikely
> to be as sturdy as a commercial one unless you put a bit of work into it.
>
> > Tyvek is also available with an inkjet printer compatible coating, but
> the company that makes this (I believe it is Dupont) used an FWA in the
> coating. It has a nice smooth matte surface, but is useless as a white
> reference.
>
> Canon sells a Tyvek-backed banner paper with the exact same coating they
> use for the "Heavyweight Coated" paper they ship with large format printers
> for initial setup. It's actually superb for its intended purpose.
>
> You're right that the coating makes the top side useless as a white
> reference...but the back side is uncoated. It's got a bit of gloss and
> texture to it that limits its suitability as a general-purpose photographic
> white reference to situations with carefully-controlled lighting, but it's
> only an hair's breadth away from Spectralon in terms of its spectral
> response. Another great alternative is tear-proof envelope mailers made of
> Tyvek, available at pretty much any office supply store. It's also a
> popular material for CD envelopes.
>
> > Also, do not over-estimate the usefulness of FWA/OB agents for papers.
> Due to light exposure and chemical processes these agents can fade rapidly
> (days to weeks), resulting in a yellowish substrate and rendering their
> purpose moot.
>
> Oh, no doubt. FWA is about the only thing that makes cheap office paper
> useable, and Hahnemühle in particular makes some truly fantastic fine art
> papers with subtle and highly effective applications of FWA; other examples
> abound across the rest of the spectrum. But, as you note, all these papers
> have limited lifespans and are not at all suitable for archival work. For
> something you know only needs to make it though the current season, maybe a
> bit longer in some cases, FWA is a fantastic option to have available. But
> if you want your children to see pretty much the same image as you yourself
> printed, FWA is guaranteed to prevent that.
>
> > There are some very white (CIECAM02 bc value < 1) papers available on
> the market. I have a list of papers without FWA/OB agents on my website at
> http://rmimaging.com/information/fine_art_paper.html. The CIECAM02 J, ac,
> and bc values for the papers are listed in the table.
>
> That's a wonderful reference you've put together -- thanks! I'll
> definitely turn to it the next time I find myself looking for "go-to"
> papers (which, with luck, won't be for a while, of course).
>
> A few notes about some specific papers on that list:
>
> Canon's Fine Art Watercolor was, for a while, my absolute favorite paper.
> With an exception I'll note in a moment, it's got the highest L* value and
> the most neutral a* value, though the b* makes it slightly yellower than
> average. More importantly, at least on my iPF8100, it's got the largest
> gamut of any matte paper I've used. Its biggest downside is a strong
> tendency to curl. However, several months, maybe an year, ago, it seemed to
> be out of production. Nobody had any in stock with no indication that more
> would be on the way. I bought what I thought might have been the last 44"
> roll on the market. But I see it listed in stock at a couple places
> today...no clue if they're making it again, if these are the last few rolls
> from a forgotten shipment, if it's a reformulation, or what.
>
> Next, you list Canon's Tyvek Banner as being as close to perfectly white
> as it gets in the real world. I'll bet you a cup of coffee or other
> suitable beverage that you got that reading from Canon's swatch book...in
> which the sample they included lacked the "Heavyweight Coated Paper"
> coating. If so, grab a sharpie and make a mark on the sample, and you'll
> see why coating is necessary. Ink -- and especially Canon printer ink (ask
> me how I know this) spreads and pools on uncoated Tyvek like you wouldn't
> believe.
>
> Still...imagine a formulation of Tyvek with much finer fibers so the grain
> isn't visible, and a clear inkjet-accepting coating, and you could well
> wind up with the ultimate for-display fine art paper. It wouldn't have the
> luxurious feel of an heavy cotton paper, but prints could potentially be
> spectacular (depending greatly on the coating, of course).
>
> On your chart, ignoring canvas and proofing and other specialty papers, it
> looks like there's a several-way tie for second place, and the Crane Museo
> Portfolio Rag might have the edge. I can report that it's as good a paper
> as you can buy. Within rounding, its gamut is the same as the Canon Fine
> Art Watercolor, though the Canon (assuming it's still the same) might have
> an imperceptible edge. The Crane feels much better in the hand. The Crane
> has the same coating on both sides; Crane tech support says this is to
> control curl and makes no guarantees about what sort of printing the back
> side is capable of, but I can't see any difference in prints front or back
> -- and, it de-curls beautifully, unlike the Canon. All together, the Crane
> is a superior paper to the Canon, except for prints that will be
> spray-mounted and never handled.
>
> Last, I don't notice any of the baryta-coated and similar semigloss papers
> on your chart. In my experience, save for the Hahnemühle offering, all are
> OBA-free or have minimal OBA levels, are very bright and neutral, and have
> excellent gamuts. I've personally settled on the Canson Platine Fibre Rag.
> Its gamut is just imperceptibly smaller than those of the competitors, but
> it's perfectly OBA-free...and the paper itself is much more luxurious than
> anything else and printable on the uncoated side. If you get a chance, you
> might want to consider adding some of these papers to your guide.
>
> Cheers,
>
> b&
>
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