If your camera works with "cheap" slaves then it will work with the Firefly 2. If it doesnt work with cheap slaves then you might need the Firefly 3.
The Firefly 2 triggers from a single pulse of light, as do "standard", "cheap" slave units. The Firefly 3 can be programmed to fire after any number of pulses, so it works with digital cameras that emit a double or triple pulse, or if youve got red-eye reduction switched on. so... if your camera doesnt work with standard slaves, because it emits multiple flash pulses, thats when you need the FF3