Is T-grain film more succeptible to airport x-ray fog?

[mahler]

Does anyone know if T-grain films are more susceptible than traditional films to fogging by airport x-ray machines? Just developed a roll of Acros that definitely shows symptoms of X-ray fogging (~2cm dark bands across the neg).

This particular roll has been through those carry-on airport machines at least 6 times or so, so this doesn't surprise me too much (and luckily, the roll didn't contain anything critical; I'd have used fresh film if it was critical). However, the rolls of traditional films (FP4+, Tri-X) that have been x-rayed as many times are still fine.

I'm just wondering if this is a reasonable explanation for what I'm seeing. Regardless, I may just toss all of the film I have now that has been x-rayed more than a few times, just to be on the safe side.


Peter

 

[roteague]

No low speed film is susceptible to fogging by airport x-rays.

 

[Sparky]

Correction: Low speed film is less sensitive to light and therefore other forms of energetic radiation- such as X-Rays. So it will develop a less intense latent image from X-Rays than, say, a film of twice the speed. But it is JUST as susceptible as any other film.

 

[mahler]

Thanks for all of the replies so far.

My understanding has always been (and still is), as Sparky alludes to, that *all* films, regardless of speed, will eventually fog, if run through these machines enough times.

My question was whether T-grain films are more susceptible to this fogging. The roll of Acros I just developed is definitely X-ray fogged, while other, traditional films that have been run through these machines the same number of times seem fine. I might be completely wrong with this hypothesis, but it's the only explanation I can think of. Maybe someone can tell me for sure one way or the other.


Peter

Correction: Low speed film is less sensitive to light and therefore other forms of energetic radiation- such as X-Rays. So it will develop a less intense latent image from X-Rays than, say, a film of twice the speed. But it is JUST as susceptible as any other film.

 

[Photo Engineer]

All film is senstive to X-ray radiation but it is proportional to grain size (speed). AAMOF, when I was at Kodak, I used X-rays to test for sharpness of films using a knife edge exposure.

Whether a given film is more or less sensitive to X-ray is based more on grain size than grain shape. It is the mean cross section of the grain that is the factor here, or the area of the grain.

PE

 

[roteague]

Correction: Low speed film is less sensitive to light and therefore other forms of energetic radiation- such as X-Rays. So it will develop a less intense latent image from X-Rays than, say, a film of twice the speed. But it is JUST as susceptible as any other film.

Yes of course, but I wasn't speaking from a technical point of view, only a practical one. Very few people will ever take low speed film through an airport x-ray enough to see any change. Frankly, I really get tired of hearing this question, over and over and over again..... It has been discussed hundreds of times here and every other internet forum.

 

[mahler]

Really? That's funny, because I've lurked on this and most of the other photo forums for years, and have never seen anyone ask about T-grain vs. traditional films as related to x-ray fogging. That's what the original question was, and that's why I asked the question in the first place. :rolleyes:

Frankly, I really get tired of people posting responses like this, which really don't help anyone at all.

PE, thanks for the helpful reply. This is precisely the answer I was looking for.

Frankly, I really get tired of hearing this question, over and over and over again..... It has been discussed hundreds of times here and every other internet forum.

 

[trip_wt]

Reciprocity failure maybe (ie the lack of in Acros)?

A possible thought,

The exposures from airport x-ray machines are I'm guessing in the region of about 5 seconds to allow the operator to see what is in the bag. And as it takes multiple passes through a machine to show any effect I would say that the exposure is well within reciprocity failure region for most films.

Acros, however, is said to suffer from very little reciprocity failure, virtually none at all in up to 2 minute exposures. So the film's effective speed for low intensity exposures is going to be greater than films which suffer badly from reciprocity failure. The other films mentioned by the OP: FP4 and TriX both suffer from pretty marked reciprocity failure so at the low intensity exposure in an x-ray scanner Acros may have a higher effective speed, and so be more fogged by the x-rays.

This of course assumes that reciprocity failure works in the same with x-rays as it does with visible light, which I don't know.
Anyone else have any thoughts on this?

 

[Sparky]

I would assume the mechanism is identical. I don't think that a silver halide molecule would really be able to tell the difference.

 

[gr82bart]

I heard it's because t-grain films have no silver ...

Regards, Art.

 

[roteague]

Really? That's funny, because I've lurked on this and most of the other photo forums for years

Then you haven't been looking. Just do a search for Fuji Acros and x-rays. Oh, and I took a box of Acros through the airport x-ray machine 6 times in one trip, no problems at all.

 

[Maris]

A bit off-topic but I'm about to start shooting 8x10 x-ray film on a regular basis. I wonder if I will be told down at the airport that it's ok to x-ray my x-ray film because x-rays won't affect it?

 

[roteague]

A bit off-topic but I'm about to start shooting 8x10 x-ray film on a regular basis. I wonder if I will be told down at the airport that it's ok to x-ray my x-ray film because x-rays won't affect it?

Right, and tell them you have a bridge in Sydney for sale when they are finished.

Which reminds me, I'll be in Sydney in about 8 days.

 

[Photo Engineer]

X-ray film itself is more sensitive to X-rays due to the large grain size and to the double coating of silver, one light sensitive layer on each side of the film. In addition, to get a good image, phosphors are used in the exposing cartridge when an x-ray is taken. This uses visible light to expose the major part of the image.

PE

 

[mahler]

That's an interesting thought, and something I hadn't thought of before. Makes sense, actually. Thanks for the helpful input.

Acros, however, is said to suffer from very little reciprocity failure, virtually none at all in up to 2 minute exposures. So the film's effective speed for low intensity exposures is going to be greater than films which suffer badly from reciprocity failure. The other films mentioned by the OP: FP4 and TriX both suffer from pretty marked reciprocity failure so at the low intensity exposure in an x-ray scanner Acros may have a higher effective speed, and so be more fogged by the x-rays.

 

[tim_walls]

The exposures from airport x-ray machines are I'm guessing in the region of about 5 seconds to allow the operator to see what is in the bag. And as it takes multiple passes through a machine to show any effect I would say that the exposure is well within reciprocity failure region for most films.

Purely speculating here, but aren't all X-Ray machines at airports digital these days? I.e. when the operator wants to freeze the image for more detailed inspection, I presumed they weren't continuing to expose the subject, just freezing a digital image.

I'm sure I've observed a static image on screen, while the conveyor is still running, which would correlate with that idea.

In fact, if I were designing an X-Ray scanner - and I think we should probably all be grateful that I'm not, so we're probably even beyond speculation here - I'd probably have a narrow X-Ray source and a single-line sensor; the complete image would be built by the movement of the goods to be scanned across the sensor, a bit like a desktop scanner.

I don't know if that's how they actually work though. If it is the case though that modern scanners use digital capture to freeze the image without further exposing the subject it would go some way to explaining why 'modern' scanners are supposed to pose less risk to your film that older technology. Maybe digital has done film a favour


(Opinions and corrections from people who do in fact know what they're talking about gladly welcomed - enquiring minds would quite like to know!)

 

[Tom Hoskinson]

Purely speculating here, but aren't all X-Ray machines at airports digital these days? I.e. when the operator wants to freeze the image for more detailed inspection, I presumed they weren't continuing to expose the subject, just freezing a digital image.

I'm sure I've observed a static image on screen, while the conveyor is still running, which would correlate with that idea.

In fact, if I were designing an X-Ray scanner - and I think we should probably all be grateful that I'm not, so we're probably even beyond speculation here - I'd probably have a narrow X-Ray source and a single-line sensor; the complete image would be built by the movement of the goods to be scanned across the sensor, a bit like a desktop scanner.

I don't know if that's how they actually work though. If it is the case though that modern scanners use digital capture to freeze the image without further exposing the subject it would go some way to explaining why 'modern' scanners are supposed to pose less risk to your film that older technology. Maybe digital has done film a favour


(Opinions and corrections from people who do in fact know what they're talking about gladly welcomed - enquiring minds would quite like to know!)

I use a Phoenix nanofocus Xray system at work (material science applications), it has a small Xray spot size, sub-micron resolution and a digital sensor
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