I believe it comes down to light availability. For me, I need 2.8 at least 9 times out of 10. 4.5 at my high school stadiums and inside school gyms won't be usable, and a lot of my shooting is fall / winter / spring sports with limited sunlight. If I was birding or shooting wildlife I would go with the 100-400 probably... But idk. With my 400-800 I almost exclusively used it at 800mm. If my lens is going to stay maxed out with its focal length, a 300 with TCs might make more sense assuming the IQ is better? Idk.
Also found this neat. 400mm vs 300mm. PMRTV has a few videos on the lenses.
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Jul 26, 2026 at 09:18 AM
Previous versions of BigBabyMoses06's message #17078484 « Sony 300mm 2.8 vs new 100-400 4.5? »
