3 ms·

Yes it is possible, and I know people are doing it. But it is a too short time to get an accurate reading on the level, a single photograph is exposed under a

Yes it is possible, and I know people are doing it. But it is a too short time to get an accurate reading on the level, a single photograph is exposed under a very short time. And a camera is probably not shielded against radiation, so it might be impossible to predict how long the actual time of exposure is.

niels_olson 16y ago
I'm a Navy physician, with an undergrad degree in physics, working at one of the Joint Task Forces assigned to the whole Fukushima mess. If this had been taken in Tokyo, which is at background, I would have said it's something else. But right there, at the reactors, they are still very much in the several mrem/hr regime. Someone could probably calculate this. I don't think the "speed value" from the EV system is going to be of much use for this calculation, though the "aperture value" will. Nor does the color of the pixel tell you anything other than the color of the pixel that was hit by a gamma ray. Never the less, a simple count could give you a pretty good first order estimate. Assume the radiation here is around 10 mrem/hr on 15 March (there may be a more accurate published estimate out there, I'm just going on trends . . . I'll reboot into Windows and see if I can get you more accurate info off our share drive). [Edit]: Okay, so the 15th was the day of the biggest releases, ranging up to 12000 μsV/hr. Reactor 2 had an explosion at 0610 local, the reactor 4 fire was from 0600 to 1116 and there was a second explosion at reactor 2 at 1006. The 12000 μSv/hr peak is around 0930 with a second peak of 8800 at about 1000. I'm just looking at a graph, but it appear to decay down to around 300 μSv/hr over the rest of the day, then there's another, unlabeled event at about midnight. The metadata says the image was taken at 0858. This is in the middle of the upsurge. The area could be anywhere between 1000 μSv/hr and 12000 μSv/hr. Are there other pictures available from different times?
- Natsu 16y ago
  There are a ton of other photos here: http://www.tepco.co.jp/en/news/110311/ http://www.tepco.co.jp/en/news/110311/ I'm not quite sure which are camera original or which have single pixel artifacts like that, though. Dr. Neal Krawetz, who runs that blog, would know though. He's an expert in digital image forensics. I suppose you could just zoom in, count pixels, then try to get timestamps & locations out of the images via JPEGsnoop or similar tools for reading the metadata, but you'd have to contend with however many different cameras they use, etc.
  - niels_olson 16y ago
    The first of the packbot pictures from today also has a small number of blown pictures. http://www.tepco.co.jp/en/news/110311/images/110417_1f_1_1.jpg http://www.tepco.co.jp/en/news/110311/images/110417_1f_1_1.j... taken at 1138 on 4/17. In thinking a bit more, I guess without knowing how that Sony camera clears its registers, we don't know how long it took for the wells to collect those gamma rays (eg: are the registered "cleansed" just before each shot? And then cleared again after the information is transferred off the sensor?). However, the "ISO" setting probably doesn't matter. The aperture will matter essentially as much as the lens matters, and considering the lens is gathering in light from that entire area, that may be significant, I just don't know.
    - lutorm 16y ago
      Aperture doesn't matter. The gammas that make those bright pixels will comfortably penetrate the shutter, lens, and the entire camera body. It's the time between erase and readout that matters, as you say, and it will act as a 4pi dipole detector.

niels_olson 16y ago

I'm a Navy physician, with an undergrad degree in physics, working at one of the Joint Task Forces assigned to the whole Fukushima mess. If this had been taken in Tokyo, which is at background, I would have said it's something else. But right there, at the reactors, they are still very much in the several mrem/hr regime. Someone could probably calculate this. I don't think the "speed value" from the EV system is going to be of much use for this calculation, though the "aperture value" will. Nor does the color of the pixel tell you anything other than the color of the pixel that was hit by a gamma ray. Never the less, a simple count could give you a pretty good first order estimate. Assume the radiation here is around 10 mrem/hr on 15 March (there may be a more accurate published estimate out there, I'm just going on trends . . . I'll reboot into Windows and see if I can get you more accurate info off our share drive). [Edit]: Okay, so the 15th was the day of the biggest releases, ranging up to 12000 μsV/hr. Reactor 2 had an explosion at 0610 local, the reactor 4 fire was from 0600 to 1116 and there was a second explosion at reactor 2 at 1006. The 12000 μSv/hr peak is around 0930 with a second peak of 8800 at about 1000. I'm just looking at a graph, but it appear to decay down to around 300 μSv/hr over the rest of the day, then there's another, unlabeled event at about midnight. The metadata says the image was taken at 0858. This is in the middle of the upsurge. The area could be anywhere between 1000 μSv/hr and 12000 μSv/hr. Are there other pictures available from different times?

Natsu 16y ago
There are a ton of other photos here: http://www.tepco.co.jp/en/news/110311/ http://www.tepco.co.jp/en/news/110311/ I'm not quite sure which are camera original or which have single pixel artifacts like that, though. Dr. Neal Krawetz, who runs that blog, would know though. He's an expert in digital image forensics. I suppose you could just zoom in, count pixels, then try to get timestamps & locations out of the images via JPEGsnoop or similar tools for reading the metadata, but you'd have to contend with however many different cameras they use, etc.
- niels_olson 16y ago
  The first of the packbot pictures from today also has a small number of blown pictures. http://www.tepco.co.jp/en/news/110311/images/110417_1f_1_1.jpg http://www.tepco.co.jp/en/news/110311/images/110417_1f_1_1.j... taken at 1138 on 4/17. In thinking a bit more, I guess without knowing how that Sony camera clears its registers, we don't know how long it took for the wells to collect those gamma rays (eg: are the registered "cleansed" just before each shot? And then cleared again after the information is transferred off the sensor?). However, the "ISO" setting probably doesn't matter. The aperture will matter essentially as much as the lens matters, and considering the lens is gathering in light from that entire area, that may be significant, I just don't know.
  - lutorm 16y ago
    Aperture doesn't matter. The gammas that make those bright pixels will comfortably penetrate the shutter, lens, and the entire camera body. It's the time between erase and readout that matters, as you say, and it will act as a 4pi dipole detector.