Canon has just announced a new 35 mm full-frame sensor that is incredibly sensitive to low-light levels. The sensor does this in part by using large pixels (19x19 microns^2), which is about 7.5 times larger than the pixel size of their other cameras. Right now the sensor is optimized for full-HD video. Here is the video Canon has released of some footage from a sensor prototype. Most impressive are the shots of the Milky Way, illuminating a person using an incense stick, and being able to shoot in moonlight as if it were daylight.
So just how sensitive is this camera? According to the specs, the camera can form a useable image at ~0.03 lux. Doing a quick back-of-the-envelope calculation, 0.03 lux corresponds to a sensitivity of about 40,000 photons hitting each pixel each second (for green light). If we shoot at 24 frames/second, this is about 2000 photons/frame/pixel–or about 0.5 femtowatts.
Any sensor will have noise associated with it. In order to get a useable image, you should have a decent signal to noise ratio. Let's say that 5% of the pixels have noise on them (corresponding to a fairly noisy image), that means each pixel experiences about 100 noise counts/second.
What is remarkable is that this takes place at room temperature. There are other sensors that have been developed for scientific applications that are much more sensitive than this Canon camera, but they must be cooled first. For example, a camera I have worked with in the past is the Andor iDus. This camera is sensitive down to the single-photon level when cooled to -80 C. This is achieved in part by using some clever electronics to reduce the readout noise and using larger pixels (26x26 microns^2). At -80 C, the camera experiences a negligible amount of dark counts/s (much less than 1). Increase this to 20 C (room temperature), and that number goes up to a couple of hundred noise counts/pixel (as best as I can tell from the specs).
This analysis should be taken with a grain of salt. The take home message is that at room temperature, the new Canon CMOS sensor performs on par with the best EMCCD cameras out there. This is seen in Canon's own tests (where they measure against a three-EMCCD). It would be interesting to see how well this new sensor performs when cooled.
I can't wait for this technology to eventually make its way into consumer-level technology.
Screen shots from the Canon Video