400 Joules is, for most applications, plenty of power. Plugged into the mains for an indoor portrait shoot I was easily using less than 1/8 or 1/16 power, even with an umbrella softbox attached. Outdoors, crank it up to full power and you can light up whole buildings (though not in the middle of the day of course).
The manufacturer’s claim of a 3.2 second full power recycle time is pretty much dead-on. Because of its design, this is the same whether you’re using the battery or the AC adapter. At half power the recharge time is about a second, and below that recycling is instantaneous.
With regards to flash duration, I don’t know where CononMark got their figure of “1/9600 second” from. Hardwired via sync cord to a Nikon D40 with an electronic shutter, I found that the flash exposure starts to decrease if I pick a shutter speed any faster than 1/250s. At that speed and slower, the camera records consistent output from the flash (see above). This is acceptable for anybody with a conventional camera wanting to shoot at their sync speed (usually 1/250s) but perhaps not as attractive to sports or fashion photographers.
The included 110mm reflector seems a bit neither-here-nor-there. It doesn’t really give you a long throw, and I prefer to use only the built-in reflector for umbrellas and brolly boxes. More crucially, the exotic Comet bayonet means that the nearest alternative is either an 180mm reflector made by CononMark, or a Comet-Bowens adapter. Neither solution is as desirable as having a Bowens S bayonet in the first place. I can see a lot of people being put off by the idea of an integral reflector too. Because of it, the spread of light doesn’t quite reach 180°, which would be irritating when trying to get the most out of big softboxes and beauty dishes. With a Bowens adapter on top of that, the “tunnel vision” could be even worse. I haven’t got an adapter to test this.
The battery hasn’t run all the way down while I’ve been using it and I haven’t the patience to sit here and test fire the flash until it does. It’s fairly standard so I would have every confidence that it will last as long as the company says it will (300 flashes at full power). If not, I could go into town and buy a new 12V battery that will.
Durability and build quality is one of the areas where CononMark may have some room for improvement. If the weakest point of the body is the liquid crystal display (assuming my misfortune isn’t merely a one-off), perhaps it needs some added protection against the inevitable knocks it will encounter. Alternatively, replace the screen with Yongnuo-style “idiot lights” or something similar? The fact that I can use the flash without a working LCD suggests it isn’t all that necessary. I was further disappointed in the battery carry case – the zip on it misses teeth every few centimetres and is generally pretty rubbish. I also managed to crack part of the power connector when I disassembled it out of curiosity.
That said, the main body is all metal and has easily taken the impact of various silly things I’ve managed to drop on it. Only the back panel is plastic. If you take care of this kit, I can see it lasting, but to become an idiot-proof location photographer’s workhorse the DD400S may have a couple of opportunities to improve yet.