Equipped for flash photography in a wide variety of situations, the Speedlite 600EX II-RT has a guide number of 197 ft. (60m) at ISO 100 to help achieve the lighting you desire. It offers 20mm to 200mm coverage, and when the extendable wide panel is pulled out, flash coverage moves as wide as 14mm. Plus, to maximize power and minimize energy consumption, the Speedlite 600EX II-RT can be directed to zoom in accordance with the camera's image sensor size (full-frame and APS-C).

The Speedlite 600EX II-RT offers significant improvements in continuous flash performance. Engineered with a combination of highly heat-resistant material, a revised optical design for suppressing gain in the panel's temperature, plus a redesigned interior structure, the Speedlite 600EX II-RT sees speed gains of 1.1 to 1.5x* self-powered, and 1.5 to 2.0x* when used with the optional Compact Battery Pack CP-E4N. An improved flash control algorithm and a redesigned Quick Flash function help to minimize unfired flashes for more reliable, continuous operation.

For comprehensive lighting setups on the go, the Speedlite 600EX II-RT offers a number of options for both wireless flash and multi-camera operation. When used with a compatible flash, or flash driver mounted on camera, the Speedlite 600EX II-RT can serve as a slave unit in an optical setup, at distances of up to 49.2 ft./15m when indoors and 32.8 ft./10m when outdoors. In addition to optical wireless flash, the Speedlite 600EX II-RT is capable of radio transmitted wireless flash where the flash units need not be in visual proximity to one another and transmission distance is extended up to 98.4 ft./30m. Among cameras with theSpeedlite 600EX II-RT attached, setups of up to 16 flash and camera units can be synchronized to take photographs simultaneously, making multi-angle and multi-directional photography setups simple. Additionally, remote shutter release can be achieved when the Speedlite 600EX II-RT is used as a slave unit with a compatible EOS digital SLR camera.

In addition to traditional optical wireless transmission, the Speedlite 600EX II-RT facilitates radio-controlled, two-way wireless transmission between up to 5 groups. Communicating on 2.4 GHz frequencies, the Speedlite 600EX II-RT does not have the same directional limitations of traditional wireless optical transmitters. Where other wireless signals can be interrupted by physical obstacles, radio controlled systems excel. Fifteen transmission channels are available, selectable manually or automatically, and radio transmission IDs can be set to prevent misfiring in the event of signal interference on the same channel.

The Speedlite 600EX II-RT is designed to maintain the high standard of dust- and water-resistant performance found on Canon's EOS-1D series of cameras. Its exterior seams are sealed to help maintain airtightness, while a dust- and water-resistant adapter mounted to the bottom of the flash surrounds and locks around the camera's hot shoe for a nearly impenetrable seal. By maintaining the overall weather-resistant surface of the EOS-1D series, the Speedlite 600EX II-RTcan bring flash photography to more places, in more environments, without compromise.

The Speedlite 600EX II-RT features a highly legible GUI for steady and efficient multi-flash control. Design refinements such as a new flash-readiness indicator on the display panel help ensure that settings are easily confirmed with a glance. New combination button and dial operations not only speed up setting changes and manual flash control, but also help avoid unintended changes through inadvertent presses of buttons for confident, convenient operation.

The Speedlite 600EX II-RT comes with a number of key accessories designed to help position, diffuse and tone its output for optimal results. The Bounce Adapter SBA-E3 widens and diffuses bounce lighting, achieving a soft effect especially in shadow areas. The SCF-E3 color hard-type filter sets include the Color Filter SCF-E3OR1, which is effective in merging ambient incandescent light with the flash’s bluish output for warm, atmospheric results. These accessories also include the Color Filter SCF-E3OR2, which is useful for balancing out the red fogging typical of interior lighting, for more natural, realistic light. Both filters attach and detach with ease for quick and smooth set-up. The Speedlite 600EX II-RT is also bundled with a soft case that is designed not only to hold all its flash accessories, but can also store the flash unit with the filter attached and has a belt loop for speedy access on the go.

The Speedlite 600EX II-RT's dot matrix LCD panel graphically displays detailed flash modes, Custom and Personal Function settings and status indicators for both master and slave units, enabling wireless configurations with more detailed information than previous flashes. A new flash-readiness indicator means the flash status can be confirmed in an instant, and backlit operation buttons mean high visibility in both bright and dark environments.

To accommodate any number of shooting styles, the Speedlite 600EX II-RT has 15 custom functions for incredible flexibility. Options include flash exposure compensation, flash exposure bracketing controls, modeling flash, AF assist control, power and energy saving features, beep and much, much more. Personal functions, like LCD panel illumination color and Master/Slave configurations, are also easily set on the Speedlite 600EX II-RT.

The Speedlite 600EX II-RT's flash head is designed for easy bounce flash, in any direction. The head can be angled 90° up, 7° down and can rotate 180° left and right. A bounce lock with release button helps things stay in place. Additionally, the Speedlite 600EX II-RT features a catchlight panel to create catch light in the eyes of the subject for a more expressive look.