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How radiation affects digital camera

Henri Rantanen 0

I recently visited the Chernobyl exclusion zone the pictures of the damaged reactor of the power plant were slightly faded, I suspected it was due to the background radiation.

I figured it was easy enough to test how radiation affects digital CMOS-sensors so I irradiated my Nikon to see what kind of effects would I get.

Exposing the camera to radiation

I built a rig to expose my camera to different levels of radiation. Two radioisotopes were used as radiation sources, Cobalt-60 which is a strong Gamma-emitter and Cesium-137 which emits Beta-particles. These yielded the highest activity levels of my samples.

Samples of different radioisotopes

In the measurements I used my trusty Russian dual-tube RADEX RD1706 Geiger Counter with a custom sticker in it.

Rig contained a lab stand holding the Geiger-counter, camera which had its sensor set the same height from the table and a laboratory scissor jack to rise and lower the isotope sample.

Testing rig with dosimeter and the DSLR

The gamma-emitter was covered with 8 mm aluminium sheet to block any Beta and Alpha-particles from reaching the sensors. For Cesium-137 paper envelope was used as an Alpha-shield. Lens was removed from the camera and replaced with thin plastic body cap.

I took 11 measurements with both isotopes from different heights swapping the lab-elevator under the the Geiger-counter and camera. Pictures were taken in RAW-format with 30 second exposures to maximize the amount of interference in the shots.

Conclusion

Radiation produces spots in the image that are caused by high energy particles hitting the CMOS-sensor. When the ray is absorbed by the electrons in the censor, they get exited and soon release their excess energy as a flash of light.

Unless the radiation is affecting the control and processing circuitry of the camera, anomalies seen on the images are not caused by ionizing radiation.


Natural background + DSLR electrical noise  
Gamma source + DSLR electrical noise

Read the whole lab-report (in Finnish) »

Verdict
  1. Camera did not take any damage during the tests
  2. Ionizing radiation can be picked up by camera’s CMOS-sensor
  3. High energy particles cause bright dots in digital images
  4. Remember to switch off camera’s manual mode if not using it
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