Way back in the dim days of 35mm film I clapped some Fuji film rated at 800 ASA into my Voigtlander caemra and put on the fastest lens I cold find - and headed for the Quarry Amphitheatre in Floreat. There was a bellydance show in the evening and I needed to stop the action. I also called on a Metz 45 CT-1 with a Televorsatz to light it.
The Metz flashes were the best of the hammerhead style at the time - might still be, for that matter. They had a massive guide number and in manual mode pumped out a real blast of light. When you attached the Televorsatz it acted as a light concentrator and the ASA rating boosted up to 1600.
This might not sound exciting in these days of the Nikon D4s or the big Canon cameras but remember at the time most hovels in Western Australia were still being lit by pine torches and small oil lamps. At least I know mine was...
Okay - reel forward to now - lots of people have DSLR cameras that have inbuilt flashes positioned just above the penta-prism. They pop up on command and provide a decent level of light for close-up or fast people shots. But they are nowhere near powerful enough for distance work. Leaving aside the obvious solution - buy a dedicated TTL flash for the camera and have done with it - we come to the modern version of the old Metz Televorsatz.
The Rogue Pop-up Flash Booster attaches to the hot shoe on top of your DSLR, and if there is a pop-up flash inside there it pops up inside the booster. The light it emits fires out through a fresnel lens on the front of the booster and this concentrates it into a stronger, smaller beam. The packaging promised up to 8X more light but that sounds like creative confusion - reckon on a doubling of ISO.
The joy of this is that the TTL system in the camera that monitors what is coming back to the lens from the subject is unaffected by the accessory - it just benefits from more light returning. Thus you use up less power each time you shoot.
The packaging says it is optimised for lenses over 100mm focal length. Should be delightful for stage shooting or sniping out individuals at big party events.
In-store now at $ 39,95.