Color me impressed. Beyond impressed. I think I might sell the 100-400 that I have.
We went to 2 national parks looking for grizzlys and on a 4 day wildlife shooting trip. I had a 300 F/2.8 L , a 100-400 L and we rented the tammy just to have some extra reach and to try it out. The Tamron was mounted on a 5D3 and a 7D2 most of the time. The Tamron exceeded any and all expectations i had about the lens. The 100-400L rarely came out of the case. In great light, the Tammy is a keeper
Take a look at some of the shots we posted on our Facebook page. The shots with the 300L were obvious with the background blur making the animals really pop. But to be Honest about it, when i got the 2x TC on the 300L, the Tamron looked pretty darn close. The fricken Tammy rocks at its price point. I think im going to try out the new Sigma 150-600 sports version and make the comparison but to me the Huge advantage is weight. Its very light for 600MM.....Build is OK to me....But to have 600MM on that 7D2 and be able to hike out and not be weighted down was such an advantage....Dragging that 300L around at 9000 Ft and hiking in the Mtns with it was a chore. The Tammy was a piece of cake
If your a hiker and want to get in there without the weight in rough Mtn Terrain, im going to lean towards the Tamron. Very close to pulling the trigger.