Apologies if this has been covered, my couple of attempts at searching for such a comparison came up empty.
I'm considering replacing my 400/F2.8 with the 300/F2.8. Getting to around 600mm would be important to me, and both lenses can get there: 300+2x or 400+1.4x.
So, my question is: how does the 300+2x compare to the 400+1.4x in terms of AF accuracy and speed, sharpness, etc?
Clearly, the 400mm lens has an advantage in that it can get to 800mm when the need arises, which is not possible with the 300mm. That would be one downside of that swap.
Thanks.
PS: I know that from an absolute sharpness perspective, the bare 600/F4 would be the winner but probably not by much. And that beast is just getting too heavy for long days of handheld bird photography, and I'm not a fan of monopods or tripods.
Mar 14, 2026 at 08:20 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
aboulenein wrote:
Apologies if this has been covered, my couple of attempts at searching for such a comparison came up empty.
I'm considering replacing my 400/F2.8 with the 300/F2.8. Getting to around 600mm would be important to me, and both lenses can get there: 300+2x or 400+1.4x.
So, my question is: how does the 300+2x compare to the 400+1.4x in terms of AF accuracy and speed, sharpness, etc?
Clearly, the 400mm lens has an advantage in that it can get to 800mm when the need arises, which is not possible with the 300mm. That would be one downside of that swap.
Thanks.
PS: I know that from an absolute sharpness perspective, the bare 600/F4 would be the winner but probably not by much. And that beast is just getting too heavy for long days of handheld bird photography, and I'm not a fan of monopods or tripods. ...Show more →
I think the other obvious downside is the 300 with the 2X is at f/5.6, whereas the 400 with the 1.4X is at f/4. That could make a big difference in how high the ISO has to go to get the shutter speed you need. At dawn and dusk and in darker environments that might really matter.
Obviously it depends on what and how you shoot.
The 300mm is lighter-- way lighter. Did I mention it was lighter??
That makes a huge difference for me if I am hand holding. As an old fart the 400 and 600 primes are getting heavy to handhold for any long period of time.
The ability to go from 300 to 420 to 600mm is more useful for me, than going from 600-1200mm
Since I purchased the 300, my 400 is only used for night sports- where the f2.8 is vital.
gary
