I'm going to chime in here with some observations after having owned the 100-400 v1 (now gone to a new home) and owning the 300/4 + x1.4 TC :
1. The 100-400 is an excellent lens up to a certain distance (and is superb for pseudo macro) but after that I found the IQ dropped off significantly more than the 300mm. The 300+TC beats it all ends up.
2. The 300mm has a brighter aperture, quicker focusing and better IS as noted above. All major benefits which go to explain the significant price difference.
3. Weight : Slightly heavier but I agree with Petrov above, the tromboning is the issue as it destabilised the combination so the weight difference isn't an issue for me per se.
A simple science experiment proves this point - a heavier weight closer to the camera feels less than a lighter weight further from the anchor point.
4. On the issue of carrying two lenses. Firstly most birds I shoot are small and there is a reason why the majority of top birding lenses are 500, 600, 800 primes, it's because you very rarely fill the frame and almost always you'll still need to crop in! And after many years birding I do have good stalking skills so getting close isn't the issue (though you can't always).
However, in the event that I get that close to larger birds, then the 40-150+TC fills that niche. That said the weight in my hands is still only the 300+OM1 and the other lens is in my backpack (or my bag is on the ground if I'm in situ) so not an issue unless I'm hiking long distances to get to the subjects.
For me it comes down to this: if you are a serious birder (esp. of smaller or distant birds) then you'll notice the difference and monetarily it's worth it. Get the x1.4 TC, the AF is still excellent and the IQ holds up superbly (90+%?).
I dithered and ummed and ahhed on forking out the money for the 300mm for 2 years - from when I first started using M43 (I finally bought a used copy from MPB - in the UK they are much better it seems than in the US), I regret not buying it much earlier.
Sep 30, 2025 at 12:27 AM
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