



In my 20-odd years of PC building and DIY electronics hackery, I have attached refrigeration units to many things: overclocked CPUs, of course, the underside of a mousepad during a particularly hot summer, and once I even made a hand-holdable single-beverage cooling device. What I've never even thought about doing, though, is strapping a Peltier cooler to the back of a digital camera to capture higher-resolution low-light photos.

For €2,190 (£2,000/$2,400), the Italian company PrimaLuce will sell you a Nikon D5500 DSLR with a dual-Peltier cooler strapped to the back, called the Nikon D5500a Cooled. In addition to the cooler, the modified camera also switches out the standard low-pass filter in front of the sensor for something that is specially tuned to be more sensitive to astronomical wavelengths of light (specifically H-alpha deep red). In case you were wondering, a normal body-only Nikon D5500 currently retails for about £400/€500, so you're paying a fair ol' premium for the modification.

The cooler itself is a Peltier capable of refrigerating the sensor down to -27 degrees Celisus (-16.6F). A Peltier cooler uses the the Peltier effect to rapidly pump heat away from one side of the cooler to the other side, where there's a heatsink and fan to dissipate the heat. Peltier coolers are incredibly power inefficient, but they're compact, and unlike standard vapour-compression refrigeration have no moving parts or circulating liquid. Back in the olden days of overclocking Peltier coolers were all the rage, but the massive power requirements—provided by an expensive, separate power supply—made them unwieldy.

There are some buttons on the back of the cooler that let you adjust the target temperature. Since the refrigeration could cause the front filter to dew up, especially in high-humidity environments, the modified camera also includes an anti-dewing system that heats it up slightly. One small issue with PrimaLuce's camera, though: the Peltier requires an external 12V 3A power source, which isn't provided. Presumably you'll need to carry a big battery with you, or be tethered to your car or house.





As for why you'd want to drop £2,000 on a refrigerated camera, the short answer is: less noise during long exposures. In the image above, the right side is the Nikon D5500 without cooling (i.e. what you'd expect from a normal DSLR), and the left side is with the cooler turned on. At first glance it might look like there are more stars on the right side, but it's actually just noise.

Electrical (from the internal circuitry) and thermal noise is always present in digital imagery, but it tends to present itself more in long exposures. Most modern DSLRs have built-in noise reduction algorithms, but they only go so far. By refrigerating the sensor, thermal noise can be reduced significantly. (Basically, if the sensor is warm, it only takes a small amount of stray electricity/energy to trigger a CMOS photosite, creating noise. Cool it down and that threshold is much higher.)

Enthusiasts of low-light photography could probably get some use out of the Nikon D5500a Cooled, but astronomy is what it's really designed for. Whack a refractor telescope (~£1,500) on the front of the camera, and you can take photos like this from your back garden: