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Firstly: Sorry it took me so long to jump in...
Secondly: James is cruisin for a well deserved bruisin from Dee...
As blacknet mentioned, please look at this post!
We've gone over this subject and beaten it to death... but as long as we are here, let me clear up some of the BS while trying to keep insults (but not criticism) to a minimum.
PLEASE VISIT MY WEBPAGE ON THE SUBJECT!
Regarding agstreet's "test"
The most obvious effect of too much radiation is an increase in film base + fog (FB+F) as blacknet was metnioning. This increase is noticable once certain conditions are met. Exposed film is usually more vulnerable to general fogging. Using unexposed film for the test is a poor way to judge anything because the theshhold for noticable effect is different from irradiated film that has been exposed prior or after exposure. The changes in the film from one or two or three X-rays may be OK for most people. Most people would not know the difference. TSA regulations are written with most people in mind. Further more, the age of the film should also make it more succeptable to as it will have recieved a dose of cosmic radiation the size of which depends on the films age. It is worth noting that film receives more radiation flying than sitting on the ground because of decreased atmospheric shielding. The same thing goes for living at 9000ft vs sea level. My film is getting 4X as much cosmic radiation as someone at sea level.
Aside from all this backround information, testing unexposed slidefilm is a rather poor choice. I would harldly call agstreet's "study" a "controlled study." Aside from the using unexposed slidefilm for the test, I don't think agstreet used test film from the same bulk roll (that slide film could have been from different batches) and I don't think he put a calibrated dosimeter through the X-ray machine to measure the dose the film recieved. Also, blackent was asking for the densitometry data, not scans of the film. If agstreet understood the process, he would proably realize that. Furthermore, from my more limited understanding on the subject of densitometry (vs radiation), blacknet is quite right that the lab probably wouldn't detect the change on their equiptment or screwed up the process on top of the testing materials being far from ideal. The rest of agstreet's claim that X-rays at airports don't harm film is scientifically dubious and based on anecdotal evidence and subjective evaluation.
Food for thought:
1. If carry on X-ray exposure doesn't matter, why are you allowed hand inspections for ALL film? The government just created the TSA and moved and altered the CFRs. It could have easily been removed and would have saved much time and effort.
2. There are lots of pros who demand hand checks. Many do this because they have had experiences with film fog that they blame on X-Ray machines.
3. Many Pros simply avoid X-rays and hand checks by buying/developing their film on site or having it shipped to and from the site. (re blacknet's comment here, I don't know how common that is... I heard it's only when shipping to certain places (military bases, government offices, etc)
4. I've spent a goodly amount of time with photography. It is a source of income for me. I don't let them X-Ray my stuff if I can help it.
5. It all comes down to two things.
A. There are *many* unkowns in this question of travel X-ray exposure effects on film. So...
B. What is acceptable to you individually. That is: What risks are you willing to take with your film considering what effects you think will be perceived based on the exposures you expect your film might receive from all sources? Is your film going to see four sessions in an X-ray macine?
To give the most extreme examples, is your film partially exposed using a modified zone system, Ilford Delta 3200 that is close to its expiration date, and you are shifting... "pushing to 12500," and the film is going to see 8 X-rays and 8 flights, or do you have some fresh 35mm Fuji RVP Velvia 50ISO you are treating like 40ISO and are going to let your kid use in his point and shoot that is going through one X-ray on a single one way flight.
Regarding agstreets confused analogies on dosage and "voltage"
I don't know what physics book agstreet read. I assume by "voltage," agstreet actually means the frequency/energy of the photons being emitted. Voltage is a measure of potential difference. Perhaps he was confused because the energy of high energy photons like X-rays are given in eV, or electron Volts, which is a measure of energy, not electric potential (voltage). The energy of the photons is directly proportional to the dosage (absorbed energy/unit mass). I don't remember excatly, but X-ray machines emit photons between 10-250 KeV. I am pretty sure I remember them mostly being around 25 KeV. Many X-ray machines emit on different (but fairly close) frequencies and then compare the absorbtion. Different materials absorb different frequenceis differently. Organics have their own absorbtion profile. IF you see a false color screen that scanner is looking at, it tell him whether he is looking at... say... plastic or metal. Back to the matter at hand, the frequencies the machines emit are fixed. Dosage, or absorbed energy, is the quantity that we are concerned about when it comes to X-rays and film, and to a lesser extent, doserate.
Regarding lead bags, "cranking up the machines," and checked luggage scanners.
I hear it all the time. "Don't bother with the lead bag. They will just crank up the machine." This is an bit of misinformation that has been passing around the internet for some time. All carry on luggage scanners in the USA can not have their power "cranked up." In the USA and most foreign countries, there are government limits established for the dose rate and/or the dose limit on a single pass (1mR in the US I do recall). The machines are supposed to be adjusted to that limit but they might be out of adjustment. However, the intensity cannot be altered by the operator if he sees a black blob. The dose could be higher if the operator leaves the X-Ray on and doesn't move the conveyor belt, however, this will not help the operator see through the lead bag. The operator will have to remove the film from the lead bag and hand inspect it.
Lugage scanners: Only the new high power CTX5xxx series scanners have variable power and these devices are only used to scan checked luggage and in special inspections of carry on luggage and you should never have your film run through them for any reason unless you are a fan of Russian Roulette. The high power mode allows a 3D X-Ray (similar to CAT) scan of suspicious objects for easier identification in order to speed up the scanning process by preventing the screeners from having to open every suspicious bag. These scanners are capable of destroying any undeveloped film of any speed if the high powered beam scans the film. These beams can deliver 300mR to your luggage.
Regarding agstreet's 95% success rate in hand checking
That's pretty impressive... care to share some techniques?
Regarding the FAA
Before the TSA was created, the most significant security regulations that concerned flying photographers were listed in Federal Aviation Regulations (FAR) 107 and 108 (parts of title 14 CFR); they are now defunct and have been moved to several Transportation Security Regulation (TSR), that is, Title 49 CFR parts 1540, 1542, and 1544. The new federal regulations are virtually identical to the previous regulations when it comes to film and photographic equipment. All screeners are TSA personell although at some airports private security forces are supervised by TSA personell (Kansas City International for example).
That is all for now.
PLEASE VISIT MY WEBPAGE ON THE SUBJECT!
Secondly: James is cruisin for a well deserved bruisin from Dee...
As blacknet mentioned, please look at this post!
We've gone over this subject and beaten it to death... but as long as we are here, let me clear up some of the BS while trying to keep insults (but not criticism) to a minimum.
PLEASE VISIT MY WEBPAGE ON THE SUBJECT!
Regarding agstreet's "test"
The most obvious effect of too much radiation is an increase in film base + fog (FB+F) as blacknet was metnioning. This increase is noticable once certain conditions are met. Exposed film is usually more vulnerable to general fogging. Using unexposed film for the test is a poor way to judge anything because the theshhold for noticable effect is different from irradiated film that has been exposed prior or after exposure. The changes in the film from one or two or three X-rays may be OK for most people. Most people would not know the difference. TSA regulations are written with most people in mind. Further more, the age of the film should also make it more succeptable to as it will have recieved a dose of cosmic radiation the size of which depends on the films age. It is worth noting that film receives more radiation flying than sitting on the ground because of decreased atmospheric shielding. The same thing goes for living at 9000ft vs sea level. My film is getting 4X as much cosmic radiation as someone at sea level.
Aside from all this backround information, testing unexposed slidefilm is a rather poor choice. I would harldly call agstreet's "study" a "controlled study." Aside from the using unexposed slidefilm for the test, I don't think agstreet used test film from the same bulk roll (that slide film could have been from different batches) and I don't think he put a calibrated dosimeter through the X-ray machine to measure the dose the film recieved. Also, blackent was asking for the densitometry data, not scans of the film. If agstreet understood the process, he would proably realize that. Furthermore, from my more limited understanding on the subject of densitometry (vs radiation), blacknet is quite right that the lab probably wouldn't detect the change on their equiptment or screwed up the process on top of the testing materials being far from ideal. The rest of agstreet's claim that X-rays at airports don't harm film is scientifically dubious and based on anecdotal evidence and subjective evaluation.
Food for thought:
1. If carry on X-ray exposure doesn't matter, why are you allowed hand inspections for ALL film? The government just created the TSA and moved and altered the CFRs. It could have easily been removed and would have saved much time and effort.
2. There are lots of pros who demand hand checks. Many do this because they have had experiences with film fog that they blame on X-Ray machines.
3. Many Pros simply avoid X-rays and hand checks by buying/developing their film on site or having it shipped to and from the site. (re blacknet's comment here, I don't know how common that is... I heard it's only when shipping to certain places (military bases, government offices, etc)
4. I've spent a goodly amount of time with photography. It is a source of income for me. I don't let them X-Ray my stuff if I can help it.
5. It all comes down to two things.
A. There are *many* unkowns in this question of travel X-ray exposure effects on film. So...
B. What is acceptable to you individually. That is: What risks are you willing to take with your film considering what effects you think will be perceived based on the exposures you expect your film might receive from all sources? Is your film going to see four sessions in an X-ray macine?
To give the most extreme examples, is your film partially exposed using a modified zone system, Ilford Delta 3200 that is close to its expiration date, and you are shifting... "pushing to 12500," and the film is going to see 8 X-rays and 8 flights, or do you have some fresh 35mm Fuji RVP Velvia 50ISO you are treating like 40ISO and are going to let your kid use in his point and shoot that is going through one X-ray on a single one way flight.
Regarding agstreets confused analogies on dosage and "voltage"
I don't know what physics book agstreet read. I assume by "voltage," agstreet actually means the frequency/energy of the photons being emitted. Voltage is a measure of potential difference. Perhaps he was confused because the energy of high energy photons like X-rays are given in eV, or electron Volts, which is a measure of energy, not electric potential (voltage). The energy of the photons is directly proportional to the dosage (absorbed energy/unit mass). I don't remember excatly, but X-ray machines emit photons between 10-250 KeV. I am pretty sure I remember them mostly being around 25 KeV. Many X-ray machines emit on different (but fairly close) frequencies and then compare the absorbtion. Different materials absorb different frequenceis differently. Organics have their own absorbtion profile. IF you see a false color screen that scanner is looking at, it tell him whether he is looking at... say... plastic or metal. Back to the matter at hand, the frequencies the machines emit are fixed. Dosage, or absorbed energy, is the quantity that we are concerned about when it comes to X-rays and film, and to a lesser extent, doserate.
Regarding lead bags, "cranking up the machines," and checked luggage scanners.
I hear it all the time. "Don't bother with the lead bag. They will just crank up the machine." This is an bit of misinformation that has been passing around the internet for some time. All carry on luggage scanners in the USA can not have their power "cranked up." In the USA and most foreign countries, there are government limits established for the dose rate and/or the dose limit on a single pass (1mR in the US I do recall). The machines are supposed to be adjusted to that limit but they might be out of adjustment. However, the intensity cannot be altered by the operator if he sees a black blob. The dose could be higher if the operator leaves the X-Ray on and doesn't move the conveyor belt, however, this will not help the operator see through the lead bag. The operator will have to remove the film from the lead bag and hand inspect it.
Lugage scanners: Only the new high power CTX5xxx series scanners have variable power and these devices are only used to scan checked luggage and in special inspections of carry on luggage and you should never have your film run through them for any reason unless you are a fan of Russian Roulette. The high power mode allows a 3D X-Ray (similar to CAT) scan of suspicious objects for easier identification in order to speed up the scanning process by preventing the screeners from having to open every suspicious bag. These scanners are capable of destroying any undeveloped film of any speed if the high powered beam scans the film. These beams can deliver 300mR to your luggage.
Regarding agstreet's 95% success rate in hand checking
That's pretty impressive... care to share some techniques?
Darn tootin!
This is an excellent line to use! Also tell them that you are pushing your film to 1000. Agstreet carries a few roles of high speed film to show the TSA. This is an excellent technique. Please see my webpage for more tips. It has links to government documents to print out and show the scanners. Also, nothing works like showing a TSA scanner something written by the TSA.
Regarding the FAA
Before the TSA was created, the most significant security regulations that concerned flying photographers were listed in Federal Aviation Regulations (FAR) 107 and 108 (parts of title 14 CFR); they are now defunct and have been moved to several Transportation Security Regulation (TSR), that is, Title 49 CFR parts 1540, 1542, and 1544. The new federal regulations are virtually identical to the previous regulations when it comes to film and photographic equipment. All screeners are TSA personell although at some airports private security forces are supervised by TSA personell (Kansas City International for example).
That is all for now.
PLEASE VISIT MY WEBPAGE ON THE SUBJECT!
