The Canon Speedlite 600EX-RT / 600EX is the flagship professional Flash. It offers a flash coverage from lens focal length 20mm to 200mm with a maximum Guide No. reaching 60 (meter; ISO 100; 200mm). A new dot-matrix LCD panel for display of all pertinent shooting information, backlit controls plus an internal sound generator. A new color filter holder helps maintain accurate color in a variety of ambient light conditions. The built-in radio triggering (Speedlite 600EX-RT Only) offers remote lighting control over distances up to 30m, effectively avoid interference due to reception angles or obstacles, and increase the flexibility of multi-flash wireless photography.