Taking a lens launched in 1999 and testing it against more current models is always going to be an interesting exercise. Fortunately for the EF300mm f/2.8L IS USM, the test data backs up what users have known for years – it really is very good. If you’ve got one and have been considering an upgrade to the Mark II version, you will find improved optical performance, though not by much. The main benefits will be in the reduction in weight (2,550g vs 2,400g) and the improved Image Stabiliser that offers up to four stops rather than two stops. Canon also claim the AF of the Mk II version is improved.
On the other hand, if you’re in the market for a 300mm lens and don’t currently own one, then your main deciding factor will be price. The EF300mm f/4L IS USM may not be quite as good as its more expensive stable-mates, but it still puts in a very respectable performance. Equally, if you can’t stretch to the cost of the latest Mk II 300mm f/2.8L, then picking up a second-hand EF300mm f/2.8L IS USM is going to offer you very similar performance, for quite a lot less money. In fact, if you don’t need the extra IS stops and the 150g weight difference is not an issue, then the older lens is probably the pick of the trio as it blends great performance with a more affordable second-hand price tag.