As good as gear is getting in general, it’s still very rare to come across a piece of kit that, after 2 years’ regular use, leaves almost nothing to be desired. Exposure’s compact Diablo helmet/bar light is just such a piece of equipment. Since purchasing my (Mk. 1) Diablo, improving electronics and LED emitters have led to two subsequent models- and an amazing 39% jump in claimed output (from 700 to 957 lumen on high). Read on to find out why the Diablo is with me on most commutes and every night ride (or ride that might turn into a night ride).
At 124g (claimed) for the Mk. 3 light and simple/secure helmet mount, the Diablo all but disappears on my head. The “weatherproof” construction (CNC machined in England) has indeed weathered some serious downpours without complaint. For 2012, the Diablo has added a covered, gold-plated Smart Port, which is used for charging, for external batteries, or to power external accessories. The back of the light now features a notch that makes the power switch (which is about the same size as the Smart Port) easier to find with gloved hands. All in all, the Diablo is a very satisfying piece of equipment to handle.
Because LEDs lose efficiency as their temperatures rise, Exposure’s Intelligent Thermal Management actively manages the power that the three Cree XPG R5 emitters see- and as a result the heat they generate. Doing so not only allows Exposure to wring the maximum light out of the LEDs under ideal conditions, but also to better manage power consumption as things heat up and keep output levels consistent during cold or warm spikes. 
The recessed collimated len- which looks like a tiny honeycomb- puts out more of a spot than some Exposure models (appropriate for a helmet mount) without any rings or abrupt changes in coverage.
Though the 1hr runtime on high may sound awfully short, dropping output to medium (a very usable ~680 lumen) or low (~475 lumen) increase the battery’s life to 3 and 10 hours, respectively. The very bright flash mode is good for days. During the shoulder seasons and in poor weather, having the flashing Diablo on my helmet allows me to easily get the attention of surrounding traffic while having plenty in reserve to ride home on medium should the day run long. When locking a bike outside, there’s nothing left on the bike- an big bonus when locking in public spaces or running late.
For mountain bike riding, adding Exposure’s $130 3-cell piggyback battery quadruples the run time to 4 hours on high. 
Sure, doing so negates some of the advantages of a self-contained lightset- but throwing a small battery in my pack is a small price to pay to enjoy nearly 1,000 lumen for four hours. Combining the Diablo with a MaXx D (which pumps out 1,200 lumen for 3 hours- or about 900 lumen for 10 hours) or any other bar light will generate giggle-inducing levels of light while allowing for imprudent off-road speeds. Because of its compact size, I have also learned to carry the Diablo along for big days out. It adds virtually nothing to a big pack but having light can make the difference between spending the night or riding out should something go wrong.
As far as complaints go, I have very few. The included helmet mount doesn’t work great with all of my helmets and it can take a bit of experimentation to find a vent that has enough room to keep the inner piece from touching my rider’s. 
Unless it’s been changed since Mk. 1, the Diablo also preferentially drains the internal battery before using any external power- not a huge deal, but worth keeping in mind for 24hr race light planning.
Though I’ve only had the Mk. 3 Diablo for a short time, my experience with the Mk. 1 (and Mrs. Marc’s experience with her Mk. 2) leave little reason to worry about the new version’s durability. US distributors Ibex Sports handle all service here in the US and, after period of purely consumer-direct sales, Exposure lights are also available through bike shops. Buying from a US shop or Ibex will ensure that the lights come with the correct charger, too- something that is pretty important.
While not as inexpensive as some generics, the Diablo is certainly competitive for its size and output. The light’s construction is probably the best that I’ve felt- an impression backed by my (and others’) experience. Really, though, it’s the form factor that makes the Diablo painless to use in commuting, mountain, and backcountry settings- and has helped me get every penny’s worth out of mine.
marc
www.exposturelights.com (international)
www.ibexsports.com (USA)
