Summary: This is a must-have for any serious photographer that uses Speedlites.The powerpack servers two functions: it reduces flash recycle time (by providing increased voltage) and increases the number of flashes you can fire before changing the batteries (by having additional 8 of them).It's fantastic at events because you don't have to replace the batteries every couple hundred shots.
Pros: Easy To Install, Lightweight, Long-Lasting, Reliable
Summary: I bought the Canon CP-E4 Power Pack because I could not power up my Canon 600EX-RT Speedlite flashgun with the batteries that I had at the time. The power pack gives very quick recycling times but at a high cost. The main problem I had with it was that when it was screwed onto the base of my Manfrotto 233B Camera Flash Bracket it had a tendency to swing round a bit. I think that it needs to be secured with a strap, probably with Velcro.
Summary: It's so useful to have supplementary power for a canon strobe as the recycle time is shorter for more flashes so it keeps you up and running. It's also nice to be able to load a cartridge of AAs which are easy to source and if rechargeable, easy to swap out for a day long outing.
Summary: Always waiting for your flash to recharge at events? Grab this!! I was hesitant at first but it now allows me to forget about whether I have enough power so I can get on with my event photography work. The pack easily attaches to your belt and the connector is strong connected to the flash/strobe head. Overall I'm pleased I spent the money on it.
Pros: Good Value, Lightweight, Long-Lasting, Reliable
Summary: A good compromise for providing the extra power that is required when second chances to capture an image are not an option. It isn't cheap, but it works and reputable alternatives are much more expensive. Have used it for weddings and it is up for the challenge of day-long use. Need more discipline to disconnect when I put the camera down or I am going to do serious damage to a camera or lens, but that is not a fault of the product.
Summary: I often take indoor event photographs where, unfortunately, flash and rapid fire is often an unavoidable combination that I need. Whilst the 580EXii is pretty rapid at recycling with only its 4 internal AAs, having this little 8xAA pack in your pocket means recycling keeps up with the camera, AND you don't really have to worry about running out of juice in a typical assignment.
Pros: Easy To Install, Lightweight, Reliable, Small
Summary: Stupidly expensive, but then what Canon accessory isn't. And for that price I'd expect some form of strap to go through the two holes the unit has in order to hang the pack on a lighting stand as surely many users will be using it to power a remotely triggered speedlite on a stand.It does do it's job well though. No regrets on the purchase.
Summary: Cette alimentation est super pratique pour qui utilise souvent son flash en condition de reportage ou de sport. Certes plus chère que les copies asiatiques mais au moins on est sûr de ne pas faire griller son flash! Quant à Digit Photo le service est comme à l'habitude hallucinant de fiabilité et de rapidité. Encore merci !