Cooling fans (or perhaps more accurately temperature regulating fans) are an unfortunate necessity on modern high resolution cameras. As we try to read more and more pixels, process them and then encode them at ever greater resolutions more and more heat is generated. Throw in higher frame rates and the need to do that processing even faster and heat becomes an issue, especially in smaller camera bodies. So forced air cooling becomes necessary if you wish to shoot uninterrupted for extended periods..
Many camcorder users complain about fan noise. Not just with the FX6 but with many modern cameras. But fans are something we need, so we need to learn to live with the noise they make. And the fan isn’t just cooling the electronics, it is carefully regulating the temperature of the camera trying to keep it within a narrow temperature range.
The fan regulates the temperature of the sensor by taking warm air from the processing electronics and passing it over fins attached to the back of the sensor. I am led to believe that at start up the fan runs for around 30 seconds to quickly warm up the sensor. From there the camera tries to hold the sensor and electronics at a constant warm temperature, not too cold, not too hot, so that the sensor noise levels and black levels remain constant. The sensor is calibrated for this slightly warm temperature.
As well as running in the default auto mode there are “minimum” and “off in record” modes for the fan in the technical section of the FX6’s main menu. Minimum forces the fan to run all the time at a low level so it doesn’t cycle on and off, possibly at higher levels. Off in record turns the fan off when recording – however the fan will still come on if there is a risk of damage due to overheating. Off in record can result in minor changes to noise as black levels during longer takes as the camera’s internal temperature rises, but you’ll likely only see this if you look carefully for it.