| Author | Message | ||
     BrianShaw Rating: N/A |
Re: John Shriver's post... You're right about the power levels of Rapiscan (and similar) carry-on baggage x-ray machines... they are 1 power and use a bunch of post-processing features to enhance the x-ray image and "bad thing" detection capabilities. My error... sorry. Rapiscan, according to factory data, guarantees 1600 ASA for 10 exposures without damage. But InVision CTX (the favored x-ray machine for checked baggage) is starting to be used for carry-on bags, too, in some places. CTX has a low-power (similar level to the Rapiscan-type systems) initial scan AND it has a high-power level that can be either operator-induced or automatic... and it will (as you say) cook film. "The InVision CTX-5000SP, produced by InVision Technologies, Inc., employs conventional x-ray and cat scan technology. The system pre-scans baggage to evaluate it for any potential threat (explosive), then scans further using a focused, more intense narrow width beam if suspicious materials are detected. This concentrated high-energy beam (1cm wide / 100 - 300 mR in power) is causing fog damage to unprocessed photographic films. By comparison, older, conventional x-ray inspection units produced less than 1mR of energy and after "many" passes through these systems, unprocessed films could exhibit a radiation caused effect. Systems employing this new technology start with an initial inspection at lower x-ray intensity. If anything is deemed suspicious about the shape, size or content of objects in the luggage, it automatically triggers additional scanning with the CTX-5000SP machine. While the CTX-5000SP and CTX-5500 are not typically used today to inspect carry-on luggage, the FAA has indicated that this technology will be implemented in the future, where practicable. Several reports of it being used for carry-on inspection have already surfaced. Tests conducted by the Photo Industry Marketing Association (PIMA) indicate that the CTX-5000SP will cause significant fogging of all unprocessed color negative films with an ISO speed of 100 or higher when the film sustains a direct hit by the machine's high intensity x-ray beam. The orientation of the fog stripe is dependent upon the orientation of the film relative to the x-ray beam. The density of the fog stripe depends upon the film speed; the faster the film the more dense the stripe. Additionally, whether this stripe is seen in the photographic print may depend upon scene content. Busy scenes with flowers, foliage, etc. may tend to obscure or lessen the x-ray effects." See http://www.kodak.com/global/en/service/publications/tib5201.jhtml for images of x-ray damage caused by checked baggage x-ray inspection. It helps clarify the type of damage that John described. |