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Ken Rockwells review of the RF 100-400


Including sample photos. Man this is a slow lens. I really need to adjust to the new paradigm.



Slow, and not as sharp at 400mm as the “L” lenses, but it does meet a certain market segment. 

Mike Sowsun
80D, 5D Mk III

My wife is disabled, so she needs a light rig. She bought the RF 100-400 for her R6 and I have to say, I am impressed with this budget lens. If you don't try to overreach, which is a mistake a lot of folks make with longer zooms, it's very sharp. We try to stay under 50 feet for our bird shots and she gets very good detail. It focuses faster than my EF 100-400L II, particularly in low light (tree canopy or in brush) and as fast as my RF 100-500L. F/8 at 400mm isn't an issue on the R5 & 6 for us because they handle higher ISO so well, particularly the R6. We typically shoot in the ISO 500-2000 range to keep shutter speed up and good DOF, with this lens that is at least 1/500 and aperture above f/10. We are both shaky, so even with IBIS & lens IS, we still need higher shutter speeds. I'll add that this lens focuses very close at 400mm, so it does extremely well shooting flowers and insects. Anyway, it's a nice lens and don't be fooled by the low price tag 🙂


"She bought the RF 100-400 for her R6 and I have to say, I am impressed with this budget lens."

So is nearly every one else who actually owns the lens. The EF L version costs $2400 new and weighs 3 pounds. The RF version costs $650 new and weighs about 1.4 pounds. By nearly all accounts, the RF version is a fabulous lens. What I am learning as an EOS RP user, is that lenses with seemingly modest specs perform better on a mirrorless than you could expect from a similar lens on a DSLR. Good purchase and you get a lot of bang for the buck, despite what the spec sheet warriors may tell you.