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Thread: Camera scanning: conservator's perspective

  1. #11
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    Re: Camera scanning: conservator's perspective

    Like!

    Thank you!
    sin eater

  2. #12
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    Re: Camera scanning: conservator's perspective

    Quote Originally Posted by rdeloe View Post
    More pixels per grain clump is better, if your objective is to record grain clumps, so if you’re scanning a fine grained film (say 15 micron grain clumps), a resolution of 5,080 ppi will allow for 3 pixels per clump. At the other end, at 6,000 ppi, you’ll be able to cover each 25 micron grain clump with around 6 pixels. So yes, it seems that 6,000 ppi not only can preserve the grain structure of most black and white films, but do it with more useful detail.

    However, depending on the film and how much detail you want in recording the grain clumps, lower resolutions might do the trick too. From this perspective, it seems the people who came up with that FADGI 2016 standard of 4,000 ppi are happy having two pixels cover each 15 micron grain particle – because that only needs 3,387 ppi.
    No. You are correct about the fact that we're discussing grain clumps, but you are way underestimating the resolution required to accurately "describe" film grain. 6,000 ppi gets you in the ballpark for Tri-X. It is most definitely not sufficient to "preserve the grain structure of most black and white films".

    One important factor you're overlooking is the effects of discrete sampling of grainy originals. Because of that, increasing resolution can sometimes actually make a scan look worse before it starts to look better. This is where the concept of "aliasing" comes in. My point about grain aliasing was that the particular mix of ~4000 ppi and Tri-X grain is a "sour spot" where the interaction between the sampling frequency and the image structure of the film makes the scanned image look distinctly worse than the original - the grain is larger and uglier than it is in the negative. For some of us who consider the grain structure an important part of what gives Tri-X its personality, or whose conservation objectives include preserving all of those attributes that make a material contribution to the esthetic character of the film, a scan at that resolution more or less ruins it.

    At substantially lower resolutions the grain mushes out entirely. Users who are comfortable with that can sharpen the resulting scanned image and be happy. At substantially higher resolutions you get into the range where there's enough descriptive power to faithfully record the fine image structure. But the FADGI standard for films up to 4x5 is just wrong for a film like Tri-X, if the objective truly is faithful reproduction.

    4000 ppi is treated as something of a magic number because that's the highest resolution that's widely available in consumer-grade equipment at prices that many amateurs can afford. But the reality is that those of us whose budgets limit us to equipment of that caliber, yet who are hoping to mimic the character of our silver gelatin enlargements in our inkjet prints from film scans, basically can't have what we want. I include myself in that group, with regret.

    "Scanning" with digital cameras adds the further complication that the vast majority of such devices use sensors with Bayer or X-Trans color filter arrays, which force interpolation in raw conversion and which mean that the actual resolution recorded in the capture falls substantially short of what you'd suppose just by counting pixels. Live-view focusing limitations pose further challenges in achieving even that.

    Now it's plain that most folks who print from scans and who are using flatbeds, dedicated film scanners or digital cameras to capture their scans aren't trying to reproduce the fine image structure of their originals, and are comfortable with low-resolution scans that are sharpened to taste for purposes of printing. In some cases they recognize the aliased character of medium-resolution scanned grain from high-speed films, and they're OK with it. There's nothing wrong with any of that. The broader lesson I would draw here is simply that it's a mistake to try to figure out how much capture resolution is sufficient, just by counting scanner PPI or digital sensor pixels or even line pairs on a test target and then doing the arithmetic to see how that maps to prints at 300 or 360 or 720 ppi. Discrete sampling and color filter arrays do complicated things to image character and make simple arithmetic on nominal resolutions or pixel counts seriously misleading.

    Instead, you try the kinds of equipment that are available at a price you can afford, look at the resulting image character and decide what you're comfortable with and what kinds of tradeoffs of cost, practicality and convenience vs ultimate image character you're prepared to make. This is, in effect, what both you and Peter have done - each of you has arrived at solutions that work for your respective purposes by applying your experience, your judgment and your common sense to the actual results you've achieved with various types of scanning equipment.

    If you're responsible for teaching this stuff, stay away from the bogus arithmetic and concentrate on demonstrating how to optimally use the available equipment to acquire scans, how to process scans with skill and good judgment for printing at desired sizes, and how to evaluate the results relative to esthetic objectives, and all will be well.
    Last edited by Oren Grad; 16-Jun-2019 at 21:03.

  3. #13

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    Re: Camera scanning: conservator's perspective

    Thanks for adding your perspective on this topic Oren.

    You can rest easy that I'm not corrupting students with bogus math. I enjoy these kinds of technical conversations because learning and growth happen at the edges of one's knowledge. You're right that faithfully reproducing the grain structure of film is not what I'm currently interested in -- for my own photography, or in my teaching.

  4. #14

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    Re: Camera scanning: conservator's perspective

    Unless the total structure of the film grains (example would be edge effects of high acutance developers on film grain edges) is completely preserved in the scan, that information will be lost in the scanning process. This is essentially adding another section of anti-aliasing filtering during the scanning process.... which will have an effect on the image information acquired then converted to digits.

    Once information is lost via the conversion to digits process, that information is not recoverable post process.... Regardless of what any technology claims. That information can be pseudo recreated by the system anticipating what might have been lost, but it will never be a absolute precise replication of what is lost.

    Does this make any difference in the print result, yes or no depending on the goals and expectations of the acquired data and what that data will be used for.


    Bernice

  5. #15

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    Re: Camera scanning: conservator's perspective

    One pixel per silver halide particle is not enough, no less than two pixels per silver halide particle would be needed and significant information contained within that silver halide particle would be lost with two pixels per silver halide particle.


    Bernice


    Quote Originally Posted by rdeloe View Post
    Silver halide particles average 0.2 to 2.0 microns, depending on the film. Assuming 1 pixel per particle, we’d have to be scanning at 25,400 ppi. Double that to capture some detail in the shape of the particle. Even the best drum scanner can’t pull that off. That’s scanning electron microscope territory.

  6. #16

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    Re: Camera scanning: conservator's perspective

    12,903 MP of scanned information from a 4x5 negative is probably enough for me. 51,613 MP just seem like overkill.


    Quote Originally Posted by Bernice Loui View Post
    One pixel per silver halide particle is not enough, no less than two pixels per silver halide particle would be needed and significant information contained within that silver halide particle would be lost with two pixels per silver halide particle.


    Bernice

  7. #17
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    Re: Camera scanning: conservator's perspective

    Quote Originally Posted by rdeloe View Post
    12,903 MP of scanned information from a 4x5 negative is probably enough for me. 51,613 MP just seem like overkill.
    Heh...

    Seriously: if one insists on trying to preserve grain structure in scans, as the film gets larger the amounts of data involved indeed quickly become absolutely staggering. A purist approach is of no use when it's completely infeasible. Probably, in a few years when we have still higher-resolution capture devices and computers with still faster processors and yet more memory, we'll be able to creep a little bit further up the size + resolution scale. But still, that basic life lesson looms large: we can't always get what we want.

    Quote Originally Posted by rdeloe View Post
    For example, in the conservation world, the goal of digitization is to create "a surrogate to the original object, replacing most needs for physical access to that original object".
    And to close the loop on this point, it's worth clarifying that there are different conservation purposes. The standard required to preserve the source object's value as historical evidence of the way the world appeared in a certain place and a certain time, isn't so demanding as the standard required to preserve all interesting attributes of the source object itself, as an independent focus of esthetic or history-of-technology interest.

  8. #18

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    Re: Camera scanning: conservator's perspective

    Harry Nyquist has spoken,,

    Depends on the need of what the image data will be used for.

    BTW, Cinema release Toy Story was done in digits, stored as a digital data base. At some point the original data base as corrupted and no longer viable. This resulted in trying to cut-paste using back-up data base bits to recreate the complete data base. To combat this problem, Cinema is done on..... Film.

    IMO, all this digital stuff is a disruptive technology intended and designed to produce economic results for the elite few. What would be more rational is for both film and digits (Analog & Digital) to coexist based on real needs rather than perceived convenience and perceived advantage of one clearly over the other. There are plus-minus to both with neither being absolutely better than the other.


    Bernice

    Quote Originally Posted by rdeloe View Post
    12,903 MP of scanned information from a 4x5 negative is probably enough for me. 51,613 MP just seem like overkill.

  9. #19
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    Re: Camera scanning: conservator's perspective

    Disruptive technology indeed!

    Weren't LVT's used to store bank data on film in fear of losing the cash? I can't find a reference right now.

    We are closer to the stone age than the stars.

    Storing Digital Data for Eternity 2015 Vint Cerf


    Right now I think film and paper prints will outlast any of our digital files...
    sin eater

  10. #20

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    Re: Camera scanning: conservator's perspective

    Quote Originally Posted by Oren Grad View Post
    And to close the loop on this point, it's worth clarifying that there are different conservation purposes. The standard required to preserve the source object's value as historical evidence of the way the world appeared in a certain place and a certain time, isn't so demanding as the standard required to preserve all interesting attributes of the source object itself, as an independent focus of esthetic or history-of-technology interest.
    I didn't want to muddy the water in my original post, but that source I mentioned addresses this topic too for those who want a brief overview. Peterson distinguishes "Object Reproduction" (Preservation Digital Object), "Content Reproduction" (easy readable, looks good) and "Speculative Artist's Intention". The last one is particularly interesting in that the conservationist is trying to show the image the way the artist intended it to be viewed, which is obviously a tricky game.

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