How to fire one or several Speedlites inside a large softbox.
The idea behind a softbox is that it takes a relatively small light source, like a Speedlite, and greatly increases the apparent size. So, rather than light coming at a subject from the small angle of a Speedlite, it comes at the subject from a wide set of angles. This means that the shadows created to one side are filled by the light coming from that side and vice versa.
Top: A Speedlite is relatively small compared to most subjects. So, the light from a Speedlite hits the subject from one side. This creates hard, distinct shadows.
Center: A softbox increases the size of the light source so that it is larger than the subject. As shown by the cyan and magenta tints, the light hits the subject from a much wider zone. So the shadows will have softer edges.
Below left: The elegance of this portrait was created by the light wrapping around the model. Center: the set was actually brightly lit and cluttered with chairs. Right: The Westcott Apollo 28″ softbox fitted with three Speedlites on a Lastolite TriFlash bracket. The OCF33 cord runs out the bottom.
Mounting Speedlites inside a softbox. Syl’s favorite set-up for this is to mount three Speedlites on the Lastolite TriFlash bracket inside the Westcott Apollo 28″ softbox. If you have just a single Speedlite, the Apollo 28″ softbox will still do a great job for you. The main advantage of using multiple Speedlites in a master/slave configuration is that each flash fires at a lower power level and thus recycles faster. In terms of the shape of the light coming out of the softbox, there is virtually no difference between using one or several Speedlites.
The Ezybox by Lastolite is another softbox that works great with Speedlites. Rather than mount the Speedlite inside the softbox, the Ezybox mounts it on a bracket at the back.
Triggering Speedlites inside a softbox. The OCF33 cord is the most economical and versatile solution for triggering a Speedlite inside of a softbox. If you have a single Speedlite, you can dial the power level up in E-TTL via FEC (flash exposure compensation) or manually. If you shoot multiple Speedlites, then connect your master to the OCF33 cord and it will send the instructions to the slaves. If you have a 580EX II and a 40D or newer camera, then you can control all the details of the Speedlite(s) from the LCD monitor on your camera.
While radio triggers could be used to fire the Speedlites inside the softbox, there are two disadvantages: control and price. With manual radio triggers, you have to open the softbox and change the power level on the Speedlite(s) by hand. With E-TTL radio triggers, you get the wireless power control, but you have to pay the price–typically $200 per flash.