Put together by B&H the Vello Flash Multiplier-Diffuser Attachment with Large Adapter Kit from Vello is a cleverly-designed modifier that's both a Fresnel and a diffuser. The Fresnel lens actually pumps out approximately three additional stops of light for activities such as wildlife photography or other long throw work like sporting events. Alternatively, the attachment comes with a diffuser that replaces the Fresnel to allow you to use it as a 5.5 x 7.8 x 6.65" softbox.
With the ability to do what seems like two opposing functions, the Flash Multiplier-Diffuser Attachment from Vello is a handy light-shaping tool that sets up and mounts on your on-camera speedlight in seconds. In its capacity as a multiplier, the modifier uses its included Fresnel lens to actually pump out approximately three additional stops of light for activities such as wildlife photography or other long throw work like sporting events.
Want a soft, flattering quality instead? No problem - the attachment comes with a diffuser that replaces the Fresnel to allow you to use it as a 5.5 x 7.8 x 6.65" softbox. With the appropriate, separately-purchased adapter ring, the Multiplier-Diffuser Attachment is compatible with the Nikon SB900 series, Canon 600, and 580 series, Canon 540EZ, 340EX, 420EX, and 430EX. It is also compatible with the Sony HVL-F42AM, and the Metz 47 AF-1 and 52 AF-1 flashes.
The Flash Multiplier Adapter for Large 1.9 x 3" Flashes from Vello allows the separately purchased Fresnel lens to be used on the flash. The lens allows the flash head's output to be increased by up to three stops for long throw work.