Olympus E-420 Flash

The Olympus E-420 features a built-in, pop-up flash, which operates in either Auto, Red-eye reduction, Red-eye reduction slow synchronization, Fill-in, Slow synchronization, Manual, or Off mode. Flash control modes consist of TTL Auto (TTL pre-flash mode), Auto, and Manual (with full, 1/4, 1/16, 1/64 power output settings). First or second curtain synchronization options are available. To release the flash from its compartment, press the flash button on the top panel to the left side of the pentamirror housing. Close it again by pushing the flash head back down. The E-420 also has a top-mounted hot shoe for attaching an external flash unit.

Flash exposure compensation can be set to three stops lower or greater, in 1/3-stop increments.

The Olympus E-420's built-in flash has a Guide Number (GN) of 12 meters or 39 feet at ISO 100. Maximum sync speed is 1/180s. Super FP shooting with shutter speeds up to 1/4,000s is available with Olympus FL-50R, FL-36R, FL-50, and FL-36 external flash units.

A Wireless mode lets the Olympus E-420 work with compatible remote flash units with wireless capability, specifically the Olympus FL-50R and FL-36R. Four separate control channels are available for wireless operation, to allow multiple photographers to work wirelessly in the same area without interfering with each other. There is also support for controlling three separate groups with individual control for flash mode and flash intensity per group. Wireless remote flash operation has generally been the province of professional photographers, but is now coming decidedly down-market. And it should, as it can dramatically simplify multi-flash shooting and make it accessible to the interested amateur.

Canon, Nikon, and Sony all make wireless flash systems, with Nikon's arguably being the most flexible of the three. With their FL-36R and FL-56R flash units, Olympus has joined the wireless-flash club, taking a page from Nikon's playbook in the mode of operation and considerable flexibility of their system. A full discussion is really beyond the scope of this brief overview, but since Olympus provided us with such great illustrations, we'll take a quick swing at it anyway.

The central idea behind all of these wireless flash systems is to use very rapid pulses of the flash tube to convey digital data between the camera and the various flash units. The illustration above (click to see a slightly larger view) shows the steps in the process, all of which happen in a surprisingly short period of time, well under a second. The sequence begins with camera's flash sending out a series of pulses to wake up the remote units, tell them what exposure mode they'll be operating in, and configure them for the upcoming exposure. It then triggers a pre-flash from all the remote units, measuring the light coming back from each group (there can be as many flashes as you like, configured in up to three control groups). The camera's CPU performs some exposure calculations, then uses its own flash head to transmit power-level commands back to each flash group. Finally, a last pulse from the camera's head triggers all the remotes to fire at their assigned power levels.

The beauty of this system is that the power and operating modes of each of the groups of remote flashes can be controlled from the camera itself. This can come in very handy when one of the flash groups is mounted up in a tree, behind a window on a set, or in some other inaccessible location. Even when the flashes are readily accessible, the ability to adjust settings without running around the room each time is far more pleasant than the alternative.

The screen shot above shows the different modes the various groups can be operated in: TTL (Through The Lens metering), Manual, or Auto. The column of figures to the right of the flash modes shows the exposure compensation adjustments (in the case of TTL and Auto modes) or power level (in the case of Manual mode) selected. The next two columns show the options for flash sync speed (x-sync or Focal Plane sync), the intensity of the AF-assist illumination cast by the flash units, and the channel they're operating on. Four separate control channels are provided, to allow multiple photographers to work in the same area without interfering with each other.

The flexibility of the Olympus E-420's flash system is quite remarkable, given the camera's entry level status and price. Entry level models from Nikon for instance don't support wireless functionality unless an expensive controller flash is attached, and don't support high speed sync ("Super FP") mode at all.