{
  "id": 398633,
  "title": "X-ray and IR data specifics",
  "url": "/competitions/vesuvius-challenge-ink-detection/discussion/398633",
  "author_name": "",
  "post_date": "2023-03-31T02:38:11.833453100Z",
  "votes": 3,
  "comment_count": 3,
  "views": 0,
  "content": "<p>Hello,</p>\n<p>I'm a particle physicist and I'd like to better understand the data.  My questions partly arise because it looks like the text is visible as roughly white in the x-ray images while the text is visible as roughly black in the IR images.</p>\n<p>Would the x-ray data be showing a pixel intensity proportional to the density?  So the darker the pixel, the lower the density, e.g. black is density of air ?</p>\n<p>The IR imaging uses lower energy light than the x-ray imaging.  I've read that the text is actually on the backside of the fragments.  So with the IR imaging, is the light also having to pass through the papyrus before interacting with the ink?  Since a fragment is thin, there will be both light going through the fragments to be detected on the other side as well as light that would reflect off the ink to be detected on the light source side.  Are the IR images made using:<br>\n1) only the reflected light?<br>\n2) only the light that transmits through the fragment?<br>\n3) a combination of both reflected and transmitted light?</p>\n<p>If they exist and are available, it might be nice to get the two separate IR reflected/transmitted images.</p>\n<p>Cheers,</p>\n<p>Ewan</p>",
  "messages": [
    {
      "id": "2203646",
      "postDate": "03/31/2023 02:38:11",
      "content": "<p>Hello,</p>\n<p>I'm a particle physicist and I'd like to better understand the data.  My questions partly arise because it looks like the text is visible as roughly white in the x-ray images while the text is visible as roughly black in the IR images.</p>\n<p>Would the x-ray data be showing a pixel intensity proportional to the density?  So the darker the pixel, the lower the density, e.g. black is density of air ?</p>\n<p>The IR imaging uses lower energy light than the x-ray imaging.  I've read that the text is actually on the backside of the fragments.  So with the IR imaging, is the light also having to pass through the papyrus before interacting with the ink?  Since a fragment is thin, there will be both light going through the fragments to be detected on the other side as well as light that would reflect off the ink to be detected on the light source side.  Are the IR images made using:<br>\n1) only the reflected light?<br>\n2) only the light that transmits through the fragment?<br>\n3) a combination of both reflected and transmitted light?</p>\n<p>If they exist and are available, it might be nice to get the two separate IR reflected/transmitted images.</p>\n<p>Cheers,</p>\n<p>Ewan</p>",
      "rawMarkdown": "Hello,\n\nI'm a particle physicist and I'd like to better understand the data.  My questions partly arise because it looks like the text is visible as roughly white in the x-ray images while the text is visible as roughly black in the IR images.\n\nWould the x-ray data be showing a pixel intensity proportional to the density?  So the darker the pixel, the lower the density, e.g. black is density of air ?\n\nThe IR imaging uses lower energy light than the x-ray imaging.  I've read that the text is actually on the backside of the fragments.  So with the IR imaging, is the light also having to pass through the papyrus before interacting with the ink?  Since a fragment is thin, there will be both light going through the fragments to be detected on the other side as well as light that would reflect off the ink to be detected on the light source side.  Are the IR images made using:\n1) only the reflected light?\n2) only the light that transmits through the fragment?\n3) a combination of both reflected and transmitted light?\n\nIf they exist and are available, it might be nice to get the two separate IR reflected/transmitted images.\n\nCheers,\n\n\nEwan",
      "votes": null
    },
    {
      "id": "2203653",
      "postDate": "03/31/2023 02:54:55",
      "content": "<blockquote>\n  <p>Would the x-ray data be showing a pixel intensity proportional to the density? So the darker the pixel, the lower the density, e.g. black is density of air ?</p>\n</blockquote>\n<p>Correct. This is standard x-ray tomography, so lower intensity means lower radiodensity and higher intensity means higher radiodensity. The absolute scale of the measurement isn't known so it's also relative radiodensity.</p>\n<blockquote>\n  <p>I've read that the text is actually on the backside of the fragments.</p>\n</blockquote>\n<p>The text is on the visible, open face of the fragment.</p>\n<blockquote>\n  <p>Are the IR images made using:<br>\n  1) only the reflected light?<br>\n  2) only the light that transmits through the fragment?<br>\n  3) a combination of both reflected and transmitted light?</p>\n</blockquote>\n<p>The only images available are reflected IR light (~940nm) from the open surface. It is possible to flip some fragments for recto/verso imaging, however the text is only on one side, so no one has done this.</p>\n<p>It is true that a single fragment may be composed of multiple layers, and thus you may have text on an under layer that is hidden from view. Afaik, no one has yet shown that IR penetrates deeply enough to reveal any of this text though.</p>",
      "rawMarkdown": "> Would the x-ray data be showing a pixel intensity proportional to the density? So the darker the pixel, the lower the density, e.g. black is density of air ?\n\nCorrect. This is standard x-ray tomography, so lower intensity means lower radiodensity and higher intensity means higher radiodensity. The absolute scale of the measurement isn't known so it's also relative radiodensity.\n\n> I've read that the text is actually on the backside of the fragments.\n\nThe text is on the visible, open face of the fragment.\n\n> Are the IR images made using:\n> 1) only the reflected light?\n> 2) only the light that transmits through the fragment?\n> 3) a combination of both reflected and transmitted light?\n\nThe only images available are reflected IR light (~940nm) from the open surface. It is possible to flip some fragments for recto/verso imaging, however the text is only on one side, so no one has done this.\n\nIt is true that a single fragment may be composed of multiple layers, and thus you may have text on an under layer that is hidden from view. Afaik, no one has yet shown that IR penetrates deeply enough to reveal any of this text though.",
      "votes": null
    },
    {
      "id": "2203672",
      "postDate": "03/31/2023 03:14:28",
      "content": "<p>Thanks for the reply; I now have a clearer understanding of how to interpret the IR data.  :)</p>",
      "rawMarkdown": "Thanks for the reply; I now have a clearer understanding of how to interpret the IR data.  :)",
      "votes": null
    },
    {
      "id": "2237650",
      "postDate": "04/27/2023 20:14:06",
      "content": "<p>Is it possible that IR and X-ray scans are shifted or skewed along each other? If so are there any estimates on the potential pixel displacement distance between the 2?</p>",
      "rawMarkdown": "Is it possible that IR and X-ray scans are shifted or skewed along each other? If so are there any estimates on the potential pixel displacement distance between the 2?",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 2203653,
      "author_name": "csparker",
      "author_url": "",
      "post_date": "03/31/2023 02:54:55",
      "content": "<blockquote>\n  <p>Would the x-ray data be showing a pixel intensity proportional to the density? So the darker the pixel, the lower the density, e.g. black is density of air ?</p>\n</blockquote>\n<p>Correct. This is standard x-ray tomography, so lower intensity means lower radiodensity and higher intensity means higher radiodensity. The absolute scale of the measurement isn't known so it's also relative radiodensity.</p>\n<blockquote>\n  <p>I've read that the text is actually on the backside of the fragments.</p>\n</blockquote>\n<p>The text is on the visible, open face of the fragment.</p>\n<blockquote>\n  <p>Are the IR images made using:<br>\n  1) only the reflected light?<br>\n  2) only the light that transmits through the fragment?<br>\n  3) a combination of both reflected and transmitted light?</p>\n</blockquote>\n<p>The only images available are reflected IR light (~940nm) from the open surface. It is possible to flip some fragments for recto/verso imaging, however the text is only on one side, so no one has done this.</p>\n<p>It is true that a single fragment may be composed of multiple layers, and thus you may have text on an under layer that is hidden from view. Afaik, no one has yet shown that IR penetrates deeply enough to reveal any of this text though.</p>",
      "votes": null,
      "replies": [
        {
          "id": 2203672,
          "author_name": "ewanhill",
          "author_url": "",
          "post_date": "03/31/2023 03:14:28",
          "content": "<p>Thanks for the reply; I now have a clearer understanding of how to interpret the IR data.  :)</p>",
          "votes": null,
          "replies": []
        }
      ]
    },
    {
      "id": 2237650,
      "author_name": "elvenmonk",
      "author_url": "",
      "post_date": "04/27/2023 20:14:06",
      "content": "<p>Is it possible that IR and X-ray scans are shifted or skewed along each other? If so are there any estimates on the potential pixel displacement distance between the 2?</p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "2203646": "Hello,\n\nI'm a particle physicist and I'd like to better understand the data.  My questions partly arise because it looks like the text is visible as roughly white in the x-ray images while the text is visible as roughly black in the IR images.\n\nWould the x-ray data be showing a pixel intensity proportional to the density?  So the darker the pixel, the lower the density, e.g. black is density of air ?\n\nThe IR imaging uses lower energy light than the x-ray imaging.  I've read that the text is actually on the backside of the fragments.  So with the IR imaging, is the light also having to pass through the papyrus before interacting with the ink?  Since a fragment is thin, there will be both light going through the fragments to be detected on the other side as well as light that would reflect off the ink to be detected on the light source side.  Are the IR images made using:\n1) only the reflected light?\n2) only the light that transmits through the fragment?\n3) a combination of both reflected and transmitted light?\n\nIf they exist and are available, it might be nice to get the two separate IR reflected/transmitted images.\n\nCheers,\n\n\nEwan",
    "2203653": "> Would the x-ray data be showing a pixel intensity proportional to the density? So the darker the pixel, the lower the density, e.g. black is density of air ?\n\nCorrect. This is standard x-ray tomography, so lower intensity means lower radiodensity and higher intensity means higher radiodensity. The absolute scale of the measurement isn't known so it's also relative radiodensity.\n\n> I've read that the text is actually on the backside of the fragments.\n\nThe text is on the visible, open face of the fragment.\n\n> Are the IR images made using:\n> 1) only the reflected light?\n> 2) only the light that transmits through the fragment?\n> 3) a combination of both reflected and transmitted light?\n\nThe only images available are reflected IR light (~940nm) from the open surface. It is possible to flip some fragments for recto/verso imaging, however the text is only on one side, so no one has done this.\n\nIt is true that a single fragment may be composed of multiple layers, and thus you may have text on an under layer that is hidden from view. Afaik, no one has yet shown that IR penetrates deeply enough to reveal any of this text though.",
    "2203672": "Thanks for the reply; I now have a clearer understanding of how to interpret the IR data.  :)",
    "2237650": "Is it possible that IR and X-ray scans are shifted or skewed along each other? If so are there any estimates on the potential pixel displacement distance between the 2?"
  },
  "source": "meta"
}