Roger Clark at ClarkVision (http://www.clarkvision.com/) has completed his review of the 7D Mark II and found the sensor to be the BEST low light Canon sensor on the market.
A few lines from his conclusion-
The data shown here for the Canon 7D Mark II indicate that the camera is operating at near perfect levels for the sensor with lower apparent read noise and impressively low pattern noise compared to all other current Canon cameras tested and better than that in the 7D Mark I. This means that for high signals, noise is dominated by photon statistics. Sensitivity is improved 14% over the 7D Mark 1, and the sensitivity per square micron is the highest that I have measured for any Canon camera to date.
The approximately 10x lower thermal dark current is a game changing factor, making this camera the top Canon camera for long exposure low light photography that I have tested. The superb autofocus system, comparable to Canon 1D series pro cameras with 65 autofocus points is another game changing innovation, as the camera is at a price point that is affordable to more people.
Read his full and extremely detailed review at http://www.clarkvision.com/reviews/evaluation-canon-7dii/
This certainly inspires me to head out and take some long exposure shots – something I have not done with the 7D Mark II at this time. I can say the 7D Mark II is one of the nicest cameras I have held in hand – feels perfect and button layout and customization are wonderful.
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