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Is it possible to capture single (refracted?) photons with a CCD in a typical digital camera? Are these more likely due to coatings, etc? I have minimal knowledge of physics, but am curious.

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  • $\begingroup$ Photomultiplier tubes are probably more likely to give distinguishable signals for single photons. $\endgroup$ – NeutronStar May 5 '15 at 15:51
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Short answer: yes. Longer answer: unlikely to be distinguishable from noise. Here's what happens: some photons may be reflected to various items in the camera, e.g., if the autofocus has its own sensor. The photons which follow the optical path to the CCD or CMOS detector have a certain probability of generating a photoelectron. This probability is called the Quantum Efficiency (QE). Now, if a photon successfully produces an electron, that's a "signal electron," which is sensed via the change in voltage it causes when dumped into a local capacitor (followed with an amplifier). The problem is that there's some amount of noise current (electrons per second) in the CCD and the electronics, so unless you have a specially designed ultra-low-noise camera whose noise current is a fraction of an electron per frame time, the signal electron won't be distinguishable from the noise.

And you and I can't generally afford such a camera :-) .

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    $\begingroup$ More pointedly when taking a picture in ordinary light levels, the single photon response will be very small compared to the average illumination of each pixels. So while the sensor may be responsive (and I have reason to believe that some are) at that level the single will be lost. $\endgroup$ – dmckee --- ex-moderator kitten May 5 '15 at 16:03

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