Your opinion please.

[sawman]

As you know I am using an old 300 f4 for my bird stuff. If I decided to get something longer for carrying around the hills what would you go for?

 

[..MD..]

what about converters mate..:shrug:

md

 

[davidbridges]

400mm 2.8

 

[StewartR]

If I decided to get something longer for carrying around the hills what would you go for?

400mm 2.8

Assuming you've got the 300mm f/4 L IS, I'd put a 1.4x Extender on it.
Or trade it for a 400mm f/5.6 L.
Or a 100-400mm f/4.5-5.6 L IS.

There seems to be some sort of law of physics that says if you want to go longer than 300mm and faster than f/5.6, the lens is going to have to be big and heavy - and therefore not really suitable for carrying around the hills. So in practical terms you need to be looking at ~400mm f/5.6, which gives you these three options.

 

[fracster]

Charlie, a 1.7 TC on your 300 will give you a lightweight 500, albeit at F6.7.

The long primes are bloody heavy mate.......

The 80-400 ain`t the best in the world, but it is far from the worst.

 

[Nod]

Bigma (50-500) or it's shorter range brother the 170-500?