New (as of 2019) airport CT scanners

[wiltw]

Yes, I’ll report back. The Provia is expired, though, so I may not get unambiguous information from that roll.

FYI, 'Expired' usually means that the color reproduction of the emulsion is more likely to have shifted somewhat. CT exposure can 'fog' or may materialize as a somewhat 'wave' pattern across the emulsion, even the non-exposed area outside the usual image area.

 

[koraks]

CT exposure can 'fog' or may materialize as a somewhat 'wave' pattern across the emulsion

The CT fog of airport scanners virtually always shows up as a layer of fairly even density that (of course) tracks with film speed. It's usually featureless and perfectly even.

 

[Agulliver]

I do think there's a little confusion. Some years ago, Kodak published data on motion picture film and checked baggage CT scans which showed the damage was in a wave pattern across the film surface. That's what one would expect from the CT scanning we're familiar with.

However these new hand/cabin baggage CT scanners seem more likely to fog the entire film. I think our very own @koraks was one of the first people to discover this in the real world.

We also know that the lower the ISO, the less damage. And just as with checked bag scans, sometimes you can get lucky. As I understand it, it is possible to adjust the dose of X-rays each item receives which may explain why some airports are saying it's OK for material under 400 ISO to be scanned....but I am not sure I'd be happy with that. Especially considering sometimes film goes through multiple checks on a trip that takes in several airports. One scan might be fine. If you're country or state hopping, you won't get lucky if your film is CT-scanned multiple times.

 

[koraks]

I think our very own @koraks was one of the first people to discover this in the real world.

To set the record straight on this - I wasn't! I've so far avoided CT damage, but I did run into a freak occurrence of regular x-ray damage on a couple of rolls of film that all went through the same scanner in either Pisa or Catania.
One of the best convincing examples of CT damage is the well-known test performed by Lina Bessonova/ADOX. Her tests all show an even fog level with no apparent pattern. Here on the forum we've seen one or two instances as well, as well as one case of Portra film distributed to China which went through a CT scanner somewhere in the logistics process; this likely was not a carry-on luggage scanner, but showed the same effect of gross overall fog with no structure/pattern.

As I understand it, it is possible to adjust the dose of X-rays each item receives

I doubt it's as simple as this. One of the reasons why I have doubts is that the people who run the CT operations on airports are generally regular airport security personnel, who by the nature of their job and the qualifications involved are exceedingly unlikely to have received much training in the domain of x-ray physics. I suspect/assume these machines run more or less 'iPhone-mode', i.e. whatever technical manipulations involved are done automatically and beyond the regular user's view (or even control). One additional reason for this is that you don't want to have security personnel (1) wasting time fiddling with settings to optimize scans and (2) you most definitely don't want to structurally miss true positives because the operator happens to consistently mess up the settings. So all combined leaves me to believe that in practice, the operator will not manually adjust dosage settings for scans, and that dosage control is done automatically by the machine's software.

 

[wiltw]

. As I understand it, it is possible to adjust the dose of X-rays each item receives which may explain why some airports are saying it's OK for material under 400 ISO to be scanned....but I am not sure I'd be happy with that.

I have read the operation manuals for a couple of CT scanners used for gate security, and they both vaguely mention a setting for closer scrutiny of a bag, but not a specific mention of dose control. Someone else replied that it was merely a review control, rather than a dose control...whether this statement was fact is not necessarily supported by explicit explanation by the manufacturer of the CT equipment.

 

[wiltw]

Reinforcing the fact that CT systems at gate security CT scanners may NOT look very 'futuristic' and rounded or bulky, compared to conventional X-ray scanners! Note the detail in the text below the photo...

 

[ntenny]

Reinforcing the fact that CT systems at gate security CT scanners may NOT look very 'futuristic' and rounded or bulky, compared to conventional X-ray scanners! Note the detail in the text below the photo...

View attachment 426877

I think this is the model they use at PDX. In person it looks pretty different from the old x-ray machines; it’s not a round glowing spaceship, but I think once you’re alerted to the issue, you can tell the difference in practice.

Allowing laptops to stay in bags is the real “tell”—but note that they didn’t do this in my recent experience at ICN.

-NT

 

[Taylor K Nankervis]

Reinforcing the fact that CT systems at gate security CT scanners may NOT look very 'futuristic' and rounded or bulky, compared to conventional X-ray scanners! Note the detail in the text below the photo...

View attachment 426877

No such boxy contraption here in Australia. Besides which, all my film is hand-inspected and has not, to my recollection, passed through any xray or CT scanner at the airports I frequent.