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Thread: Recent XRay Experience

  1. #11
    Whatever David A. Goldfarb's Avatar
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    Re: Recent XRay Experience

    I use the lead bags when I'm carrying 4x5" to reduce exposure. I always carry the film on the plane.

    My understanding is that they cannot crank up the radiation on those machines (which would likely pose a hazard to the inspectors and passengers). They can increase the gain on the sensor, which does not increase X-ray exposure.

  2. #12

    Re: Recent XRay Experience

    David,

    That's my understanding as well. It's a common misunderstanding of the technology that most people think that increasing the gain increases the exposure. In fact, it's also not the case that the exposure happens continuously. It takes a snapshot of the bag, so while they are looking at the image on the screen, the bag is not continuously getting more exposure.

    Kirk, any chance you were flying during heavy solar flares or sunspot activity? It's my understanding that the exposure from those can equal the exposure from the machines (or worse) when the sun is acting up. The airlines are very careful to monitor the flight times of their crews to ensure they are not getting too much high altitude exposure.


    ---Michael

  3. #13

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    Re: Recent XRay Experience

    Kirk was the fog even? Getting .20 density of fog is not a good thing but if the fog is even and not streaky you can always print through the density. Granted it will lower contrast and increase grain.

  4. #14

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    Re: Recent XRay Experience

    Quote Originally Posted by Michael Mutmansky View Post
    any chance you were flying during heavy solar flares or sunspot activity?
    Check here http://www.sec.noaa.gov/alerts/alerts_timeline.html and around this website to find this info...

  5. #15
    Michael E. Gordon
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    Re: Recent XRay Experience

    Kirk: I've had nothing but problems trying to get hand checks internationally (fortunately no fogged film), but never domestically. TSA is obligated to hand check "sheet, large format" by their own guidelines: http://www.tsa.gov/travelers/airtrav...rial_1035.shtm I carry a copy of this and produce it if any TSA employee gives me lip. It's not a bad idea to also carry a tent if TSA insists on opening a box of film, but that hasn't been an issue for me. I have never had my sheet film x-rayed domestically and will not allow it.

  6. #16
    Kirk Gittings's Avatar
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    Re: Recent XRay Experience

    Brian, It was very even because I had a couple of blank sheets to look at (Duh!)
    Thanks,
    Kirk

    at age 73:
    "The woods are lovely, dark and deep,
    But I have promises to keep,
    And miles to go before I sleep,
    And miles to go before I sleep"

  7. #17

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    Re: Recent XRay Experience

    Quote Originally Posted by Kirk Gittings View Post
    Some notes:
    1) I have had very mixed results with asking for hand inspection.
    2) I have not tested lead bags as I understood that they would simply crank up the power to see through them.

    This is like playing Russian Roulette with your film. Regardless of the cause, the only really safe thing to do is ship it separately.
    The TSA cannot "crank up the dosage". There is one setting only.

  8. #18

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    Re: Recent XRay Experience

    Kirk, looks like your film wasn't the only thing fogged!! (sorry, couldn't resist).

    Don't know how old this link is, but Kodak (they still make film??!!!!) warned of this.

    http://www.kodak.com/US/en/motion/su..._airport.jhtml

  9. #19

    Re: Recent XRay Experience

    So what does happen when they stop the belt and stare at the image on the monitor? I've always assumed this meant the article on the belt was being exposed to x-rays for the duration it was stopped. If this assumption is correct, why would the film not be fogged?

  10. #20

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    Re: Recent XRay Experience

    Tim-
    No, airport x-ray machines are "scanning" in that they make one continuous pass. There is no "staring" or "dwelling" with this process. The stopped image is going through an intensification and conversion process (all digital now), which consumes computer processor resources so it takes time. To "see" x-rays requires a surface on the opposite side of the item being scanned that emits photons (e.g. phosphorescent screen). At hospitals and your dentist office these photons expose sheet film (very high silver density film, btw, to record this low energy event). Airport x-rays use CCDs like digital cameras to detect the photons from the phosphorescent screen that gets bombarded with x-rays. The false image is formed as some items (dense) block or reduce the amount of x-rays that are transmitted. The false image is converted to something that a non-image expert (aka TSA person) can look at and make a resonable intrepretation. The belt stops so that something doesn't pass through without getting an image made while the person looks at the current image. FYI, power levels are changeable, but not by airport personnel, only by authorized service people and it is done inside the machine. The reason that the belt backs up and then goes forward is that a new scan is being made, but this sometimes required with old technology. Doing that today with the newer/current machines is a waste of time for the operator, as the image won't change. If they need to rescan for a better "view" of something, they should pull the item and put it back on the belt in a different orientation. Some TSAer's get it, some don't. X-ray is "out of band" from visible portion of electromagnetic spectrum, but with sufficient energy levels, electrons can get released and a photon-like event occurs.

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