I've got three down jackets (Alpkit and 2 Montanes) but my recommendation is a Montane Featherlite Down. Also I'd definitely buy a hooded jacket, it far outperforms any hat & neck gaiter combo if its windproof.
Its lightweight, small pack size and windproof, perfect for photography as its not huge to pack or carry and you can wear it on the move without overheating. It won't keep you alive in the Arctic however. I can squeeze it (large size) into an unoccupied space for DSLR and lens in the Lowepro 400AW pack
Down is lighter and can be compressed more than synthetic fibres, but is rendered useless if it get wets, so I also carry a waterproof shell in the hills.