NikonGear'23
Gear Talk => Camera Talk => Topic started by: RonVol on May 30, 2016, 03:27:33
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Take a close look at the image via the link below, taken on board the ISS with Nikon D4 @ ISO 1600.
Notice the mis-firing photo sites..........at least that's what I think it is.
Could it be that the charged particles streaming from the Sun (mostly electrons, protons and alpha particles) are causing this..................hmmmmm
https://www.flickr.com/photos/timpeake/26721236693/sizes/o/
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I am certainly no expert, but I do know that they have to harden a lot of electronics for space service because of much higher ambient levels of all spectrum of radiation. And I do know that during some solar storms (e.g., coronal mass ejections), substantial steps are taken to protect certain space assets. So, I suspect that your hypothesis is correct - pixels reacting to rogue radiation.
Great find.
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The typical maximum depth an alpha particle can travel in matter is roughly 7 cm. Assuming the pictures were taken from inside the ISS, alpha particles are unlikely to be the cause.
Starting here you can find some information on the radiation levels inside the ISS: http://www.nasa.gov/mission_pages/station/research/experiments/1043.html
The New Scientist is not happy with the results: https://www.newscientist.com/article/dn2956-space-station-radiation-shields-disappointing/
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Solar wind is charged particles up to about 10 keV. That is not terribly penetrating radiation. Cosmic rays have much higher energies occasionally exceeding TeV.
The are very penetrating. Outside the atmosphere providing a shielding of (1kg mass per cm^2) there is about 100 times as much cosmic radiation than at sea level.
A cosmic ray shower can be captured as by the camera sensor with a result as shown in the linked image. But, cosmic rays can also do permanent damage to the sensor, hot pixels. We have not enough information from the single example image, whether it shows a cosmic ray detection or the hot pixels. The hot pixels will always show in sufficiently dark parts of the image. My standard procedure to identify hot pixels is, to do multiple black frames with exposure of 1/5s at ISO 1600. (exposure short enough to avoid Nikon's HPS suppression)
Some hot pixels can be healed by thermal cycling (very limited for a standard camera system). Some other hot pixels are permanent. They can only dealt with, by substituting OK image data from the neighborhood. This is sometimes termed remapping of hot pixels. Newer Nikon cameras have a user controllable feature (not mentioned in the manual) to remap hot pixels: just run sensor clean manually twice in immediate succession.
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Thanks for the replies everyone :)
An interesting discussion.
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Newer Nikon cameras have a user controllable feature (not mentioned in the manual) to remap hot pixels: just run sensor clean manually twice in immediate succession.
Do you know which cameras are "Newer." e.g. is a D800 like mine newer even though it seems very old with the release of the D5.
Dave
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I would like to relaunch the subject i.e. the question: "Can somebody confirm that pushing twice "sensor cleaning " initiates a pixel remapping" ? Thanks.
SEE DEDICATED THREAD.