Whether you use a flash as main light or a fill, the Kirk FX-1 Flash X-Tender is a must with lenses 300 mm or longer. This unit weighs less than 3 ounces and folds flat for storage. The Flash X-Tender increases your flash output by a minimum of 2 full stops (3 stops from a flash's 50 mm setting).
The Kirk FX-1 Flash X-Tender fits the Nikon SB-24 & SB 28, the Canon 430 EZ & 199D, the Minolta 5200 & 5400 and the Pentax 5000AF. The measurement between the ears of an FX-1 is 1-9/16".