The RED EPIC and SCARLET cameras are impressive feats of engineering when you consider what's been squeezed into such a tiny package, but the downside to the small size is that internal heat can become an issue. When the camera is in danger of overheating, the fans ramp up to a much higher speed, which some have referred to as sounding like a "hair dryer" or "vacuum cleaner." It doesn't take an audio engineer to understand that this could be a problem on set, and it's quite easy for a take to be ruined by the fans. Well, all of these issues are about to be history as it looks like RED has solved the problem.
Jarred Land recently posted that the RED engineers have developed a new smart algorithm for controlling fan speed (and therefore fan noise):
The new algorithm constantly monitors temperature and fan speed and starts quieter than the existing quiet setting for the first few minutes and then slowly steps up fan speed up as temperature increases the longer the take goes.. and maintains the camera temperature in doing so indefinitely while still keeping well under 30db. You can tweak that target point as needed in case your sound guy prefers a more consistent speed for a certain duration etc.
Expect this in the next big dot release firmware, and the algorithms will also include control of the new quieter top grill fan and the new front fan we will be showing at NAB.
So while the lowest setting is 25% for both cameras, once they are about to overheat the fans kick in to save the bodies from overheating. This will no longer happen once the next major firmware version is released, as they have been able to work out a new smart setting that will allow the fans to remain at a relatively quiet level for very long recording times. This will be particularly good for those who shoot documentaries on RED, as they won't have to worry about fan noise ruining an interview. It's not quite clear what speed the fan will need to run at between takes, but based on the graph above, it looks like the camera should be able to run for hours at a relatively quiet speed -- so you likely won't have to revert to the vacuum cleaner speed in order to cool the camera when you're not shooting.
Jarred also mentioned that RED is working on brand new top and front fans, which they will be showing off at NAB. While the firmware will be free, the new fans will be an optional paid upgrade. I'm sure these are designed to be even quieter than the current versions, so RED has certainly been listening to users who have been looking for a solution to the noise issues.