Testing CT Scanners: Here’s how badly they can damage your photographic film

Recently, Kodak, Fujifilm and ILFORD have issued warnings about new and enhanced scanning technology (CT scanners) at airports and other transit hubs causing serious damage to unprocessed photographic film.

Fujifilm noted that these new scanners could lead to “fogging”, distortion in shadow detail and general image degradation. Although I take Kodak, Fujifilm and ILFORD’s word for it, I hadn’t seen any examples of the effect of these new scanners on unprocessed film yet. As I was travelling through Amsterdam’s Schiphol airport recently, I thought I would sacrifice a roll of film to see what the damage looks like.

Before the results, I’d like to talk a little about my approach:

Methodology

Film, camera and exposures
Two unexpired rolls of Fujifilm Pro 400H from the same batch. One roll travelled through a new CT scanner and an X-ray scanner, the other (my control roll) did not.

I shot the film in my Hasselblad 500C/M using a Sonnar 180mm f/4 CF lens. The ambient light between exposures was cloudy and did not change. I used two film backs and as such, the time between exposures was minimal.

I took three exposures of four different subjects on both rolls, one “correct” exposure, one that was overexposed by a stop and one that was underexposed by a stop

For brevity, I have only included the results for one of the subjects (thus including three pictures per roll).

Development and scanning
I processed both rolls at home in the same tank to ensure that they were developed identically. To scan the film, I used a Nikon Coolscan LS-8000 and scanned using VueScan software. I scanned the film as an “image” and did not perform any conversion within VueScan. The files were saved in RAW DNG format.

The scans were named and performed as follows:

  • No_CT_+0: This was my “control roll” that did not pass through the CT scanner.
  • CT_+0_Locked: This was “CT scanned” roll and used the same VueScan exposure settings as above.
  • CT_+1_Unlocked: This was CT scanned roll but used automatically selected exposure settings in VueScan to see how much could be recovered.

I used this approach in order to see how the scans from my control and CT rolls would differ based on the exact same settings being used. Scanners and scanning software will always try to optimise a scan and as a result, it would be harder to compare the true effect of the CT scan on the film. Locking the exposure for this test provides an excellent method of comparison.

The third set of scans were designed to see how much VueScan could recover from the CT scanned negatives.

This process was then repeated for the one-stop overexposed and one-stop underexposure exposures.

Negative inversion/processing:
In principle, as the film is from the same batch, developed in the same tank, scanned using the same scanner and scanner exposure settings, two identical frames from each roll should look identical if the CT scanner were to have had no effect.

I inverted my No_CT_+0 exposure using Negative Lab Pro and then “synced scenes” to invert the CT_+0_locked exposure. After inversion, I tweaked the colours, highlights and shadows somewhat for No_CT_+0 and copied these over to my CT_+0_Locked scans.

For the final, “recovered” scans, I inverted each CT_+0_unlocked exposure individually and calibrated the output as best I could manually to match the No_CT_+0 exposure. By doing so I hoped to find out to what extent the effects of the CT scanner, if there were to be any, could be mitigated.

This process was then repeated for the one-stop overexposed and one-stop underexposure exposures.

Results

After opening my development tank, signs of base fog made it immediately clear which film had been through the CT scanner. After letting the film dry this fog was somewhat less apparent, although still noticeable:

The film on the bottom went through a CT scanner and shows clear signs of base fog (the orange base is significantly darker).

Although the film showed clear signs of fogging, the images were still clearly visible. I was anxious to put them into the scanner and check exactly what the exact damage was.

Below are the inverted scans for my control roll of Fujifilm Pro 400H that did not go through the scanner — No_CT_+0. Nothing new here: all exposures look very similar, as is to be expected of professional colour negative film. Nonetheless, it was nice to have verified this for myself.

Bracketed scans from left to right: underexposed one-stop, “correct” exposure and overexposed one-stop.

Now to the more interesting results. What would the images look like when scanning the film that had gone through the CT scanner?

First, the results from CT_+0_Locked, which used the same scanner exposure settings and inversion settings as the control. Given my methodology, if there was no damage, these should look identical. Well…

Bracketed scans from left to right: underexposed one-stop, “correct” exposure and overexposed one-stop.

The results are clear. There is an obvious degradation in image quality. The negatives have clearly been fogged due to the CT scanner. This is most apparent in the current setup for the underexposed image (left). as described above, these negatives were scanned with VueScan’s exposure settings locked to the control roll.

To see how much of this image degradation could be recovered, I unlocked the exposure settings and scanned again, allowing the VueScan to set the relevant gain for each frame.

Again, bracketed scans from left to right: underexposed one-stop, “correct” exposure and overexposed one-stop.

It is clear that to some degree the images are able to be salvaged. However, there are still clear signs of fogging throughout the frame. This is most apparent for the underexposed frame. Furthermore, there are some colour shifts in the image and loss in shadow detail. Lastly, the frames that went through the CT scanner are considerably more grainy, as this 100% crop shows:

From left to right: control roll (“correct” exposure) and recovered CT scanned roll (also “correct” exposure).

Conclusion

It should come as no surprise that my findings support the warnings issued by Kodak, Fujifilm and ILFORD. Nonetheless, I found it useful to have some direct examples of what happens when photographic film travels through these new CT scanners. In my experience, these scanners lead to significantly fogged film, colour shifts, loss in shadow detail and a substantial increase in grain.

I should make it clear that the film (in this case) did still produce images after one pass through the CT scanner and xray and, depending on your definition, are still somewhat usable. Some additional caveats and notes:

Although my recovered images were still usable, this is no guarantee that this is the case for every type of film and every scanner. Fujifilm Pro 400H is a “Pro” film and other offerings aimed at casual film photographers may not. In addition, this test was performed using colour negative film. Black and white negative/slide and colour slide film will no doubt exhibit different responses to the new CT scanners.

In my opinion, you should always bring your undeveloped film in your carry-on luggage and ask for a hand inspection. I should also say that I understand that in these turbulent times this post may not be that relevant. Nonetheless, after accumulating this knowledge I wished to share it with the analog community. Stay safe!

I am a hobbyist and only started with analog photography (relatively) recently. I did my best to create a fair comparison, however, it will by no means be as rigorous as the testing done by Kodak for example. Please interpret the results as such. It is entirely possible that I made some mistakes in this post or in my process. If you have any comments or disagree with anything, feel free to let me know in the comments.

Finally, these images have been scaled down to 2000px on the long edge. The full-size 5500-6000px images can be found on Imgur.

Thanks for reading and please share your thoughts and experiences in the comments section below.

~ Jelmer

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Jelmer Quist
Jelmer Quist
I'm Jelmer, an amateur photographer who started shooting on film around three years ago. I mainly focus on landscape, travel and "everyday life" photography. I enjoy shooting 120 and 35mm formats, mainly on my Hasselblad 500C/M and Nikon F3, and develop all my film at home.

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6 COMMENTS

  1. Thanks for doing this test, it’s great to see a reasonably scientific comparison and not just anecdotes. I’ve never bothered with hand checks before but now I will!

  2. Thank you for working through this example. I’m assuming that B&W film may turn out even worse. I’ll check out your web post.

  3. An interesting experiment! thanks for sharing. I my (limited) experience the guys operating the machine have very different behaviours. When asked to not put film though it, some ignored it and demanded it be scanned anyways because there were logograms of a computer and of a camera on the scanner, others made me open each single box and swiped the leaders for explosives (I started to worry he’s ask me to pull the whole film out too)… and some casually looked at the little pile and handed it back to me.
    Of course the discerning Hipster would say “instant expired film! Can you pass it through one more time sir? Please?”

  4. Appreciate the effort in going through this experiment. Been always curious about the effect and good to see some evidence here.

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