[HN Gopher] 19th-century photography technique employed in novel...
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19th-century photography technique employed in novel data storage
method
Author : abe94
Score : 42 points
Date : 2024-10-24 20:22 UTC (1 days ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| throwup238 wrote:
| _> While working on one DARPA-funded project, Solomon stumbled
| upon a page in a century-old optics textbook that caught his eye.
| It described a method developed by noted physicist Gabriel
| Lippmann for producing color photographs. Instead of using film
| or dyes, Lippmann created photos by using a glass plate coated
| with a specially formulated silver halide emulsion._
|
| This method of color photography is absolutely fascinating and
| resulted in some of the best color photographs of the early 20th
| century.
|
| The Library of Congress has a collection [1] of plates by
| Prokudin-Gorskii who was hired by the Czar to ride around Russia
| on a train and photograph the country in the years before WWI and
| the Revolution. In the last couple of decades someone restored
| and digitally aligned each color plate so now we have nearly
| 1,500 relatively high resolution color photographs of imperial
| Russia. He took photos of everything from Emirs to peasant girls
| to Tolstoy and all the architecture and scenery in between.
|
| [1] https://www.loc.gov/collections/prokudin-gorskii/about-
| this-...
| formerly_proven wrote:
| Prokudin-Gorskii's images are fascinating, but he didn't use
| Lippmann plates. Gorskii took three images using red, green and
| blue filters. That was also much more practical, because I
| don't think you can reproduce Lippmann plates, while you _can_
| print a positive RGB image with CMY(K) dyes. That 's why
| they're CMY after all (cyan absorbs red, magenta absorbs green,
| yellow absorbs blue).
| throwup238 wrote:
| Thank you for the correction! I didn't realize that there
| were multiple different plate emulsion methods.
| jazzyjackson wrote:
| This is the first I'm hearing about this lack of
| reproducibility, I can't make sense of it, you could always
| just take a picture of the resulting plate, no? Except color
| photos weren't a thing yet, so there just wasn't the
| technology at the time to make multiple copies?
| ajb wrote:
| Sounds plausible.
|
| A the start of the photo era, the state of the art for
| illustrations was for them to be drawn by an artist and
| then engraved on a wood block, manually, that was then used
| as a printing plate. There was a period when no method was
| available to convert photos to printing plates, so from
| that period you find prints of photos where someone has
| manually copied it to a wood engraving for publication.
| jazzyjackson wrote:
| Wow, reading the wiki article on Lippmann plates, sounds almost
| like a hologram - baking a diffraction pattern into glass that
| is then 'replayed' by white light. It puzzled me when it says
| one of the disadvantages was that the resulting plate could not
| be copied - like the optical effect doesn't work on film? I
| don't understand. Another citation regards this as a feature-
| not-a-bug, pointing to its use in security documents,
| apparently used on UK passports (identical hologram on all
| passports) and individuated holograms on new German passports.
| "Lippmann OVD" - optically variable device.
|
| https://holowiki.org/wiki/Lippmann_Security
| abe94 wrote:
| very cool thanks for the link - do we know of any other
| photographers with similar styles?
| readthenotes1 wrote:
| Bait And switch title....
| dang wrote:
| We've put the subtitle up there now
| oh_my_goodness wrote:
| It's difficult to understand the math on the storage density.
| Four colors out of a possible 32 colors is about 15 bits of
| information, not 40,000 bits of information.[1] If it's 15 bits
| per pixel and 115M pixels, then the capacity is 1.7Gb, not 4.6Tb.
|
| Maybe I've misunderstood the coding. Corrections are welcome.
|
| [1] Crude overestimate, assume 5 bits per color for 20 bits per
| pixel. More accurate is log2(32 choose 4), which you can type
| into Google to get 15 bits.
| jazzyjackson wrote:
| Here's the math in the cited paper... I feel like they're
| making an error of 35960 as 36kilobits instead of, yeah, 15bits
| ?
|
| https://ieeexplore.ieee.org/document/9438269
|
| If, in our previous example, the 4 wavelengths were to be
| selected from a palette of 32 different wavelengths, a single
| worfel location could store ~36 Kilobits of data. Thus, a 1 cm2
| media with 10m2 data locations (8m2 worfels with 2m spacing on
| all sides) = 1,000,000 worfels/cm2. For example, (32!/((32-4)!
| * 4!)) = 35,960 distinct states. (An analogous use of formula
| (1) is drawing a hand of 5 playing cards from a 52-card deck
| yields 2,598,960 distinct hands.)
|
| Applying the 35,960-state permutation table for k=4 (i.e.,
| superimposing 4 wavelengths per worfel), and drawing from a
| palette, N, of 32 different wavelengths, yields 35,960,000,000
| bits ([?]35.9 gigabits) per cm2; or 35.9 x (6.42 cm2 per square
| inch) [?] 230.4 gigabits/in2. And so for an example of a
| 4''x5'' media (20 in2), 20 x 230.4 [?] 4.6 terabits per 4x5
| inch media.
| oh_my_goodness wrote:
| Thanks. I believe choosing from 35,960 possible states only
| takes 15 bits, not 35,960 bits. But it's late on a Friday.
| jazzyjackson wrote:
| Yeah, there might be one more combinatorial explosion, so
| they can choose one of 16 combinations with each of those
| 35960 combinations... breaks one's brain.
| oh_my_goodness wrote:
| I hope so. That would be cool.
| formerly_proven wrote:
| > While Rosenthal was visiting the International Space Station
| headquarters in Montgomery, Ala., in 2013, a top scientist said,
| "'The data stored on the station gets erased every 24 hours by
| cosmic rays,'" Rosenthal recalls. "'And we have to keep rewriting
| the data over and over and over again.'"
|
| This doesn't seem right to me, considering the amount and age of
| COTS hardware with a variety of flash-storage in them (Thinkpads,
| Nikon DSLRs etc.)
| pcl wrote:
| Perhaps the more precise phrasing would be that the data is
| corrupted within a short enough period of time that they need
| to rewrite every 24 hours to ensure validity.
|
| IIRC the shuttle's magnetic-coil memory was hardened explicitly
| to defend against this sort of corruption, with additional
| windings to maintain a stronger charge state than would be used
| within the shield of the atmosphere.
| jazzyjackson wrote:
| Maybe a bit gets flipped every 24 hours but yeah cosmic rays
| don't just erase a whole drive... bit of a case of telephone
| here tho, just relaying a moment of inspiration.
| swayvil wrote:
| >19th-century photography technique employed in novel data
| storage method
|
| TECHNIQUE and METHOD are synonymous terms (don't quibble). Does
| anybody else find it irksome to build a sentence this way?
| Koshkin wrote:
| Depends on the context, I guess. In some, a method can involve
| multiple techniques; some of these techniques can be borrowed
| from other, unrelated, methods. (You _could_ say that a
| photograph is kind of data storage, but still.)
| hnlmorg wrote:
| I find the sentence easy to parse. So I'm curious, how would
| you have phrased it?
| fanf2 wrote:
| This reminds me of the IBM 1360 photodigital storage system,
| designed for the CIA to store a terabit of data in the 1960s.
| https://en.wikipedia.org/wiki/IBM_1360
|
| It was basically cathode ray tubes to expose photographic strips,
| an automatic chemical photo wet lab, robotic storage and
| retrieval of the developed film strips, and optical readout.
|
| Absolutely bonkers.
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