I have a Canon kit, which comprises of 4 lenses:
- a 17-40 mm f4
- a 50mm f1.8
- a 100mm 2.8 Macro, and
- a 70-300mm IS USM (non L)
I am looking for a telephoto/supertelephoto to replace #4 above.
I am looking at the 70-200 f2.8L IS II and 100-400 4.5-5.6L IS II. Now these two are definitely not cheap, there are non IS versions which are nearly half price. And then irrespective of the IS/non-IS feature, I see the 4/4.5-5.6L lenses are comparatively cheaper than the 2.8L ones.
I also plan to get a 2xIII extender.
Now what I am not sure about is how much a 2.8 vs 4/4.5 (or 5.6 at 400mm) will differ in output. Given that I will hardly be shooting without a tripod at night, do I really need a 2.8 for mid day (well lit conditions) usage? I don't think there will be any visible/perceivable difference in the DOF at larger focal lengths (please correct me if I am wrong).
If there anything else I need to look at before I make a decision on which one to go for? It's a one-time purchase, meaning I plan to make a purchase which will last me more than few years, and hence not shying from spending on a quality Canon lens. I just need to be sure (and well informed) on what I am putting the money on.
I have a Canon 5D Mk III (full frame).
The existing lens (70-300) is very very old (nearly 8 years). All the pictures I take using this existing telephoto I have, are extremely grainy (not sure why). Also the auto-focus seems to have slowed down (not sure if this is actually a possibility). I need a better telephoto lens (or kit - lens + extender whichever fits the budget) which is sharper and more durable.
Any advice is greatly appreciated.