XF100-400 + 1.4tc versus 150-600mm

Mark Levine wrote:

I am an enthusiast bird photographer currently using X-S10 with 100-400 plus the 1.4tc. Initially I was disappointed in the 1.4tc because of the negative impact on autofocus, especially with birds-in-flight at 400mm. I've gotten better at zooming out to autofocus, then zooming in while tracking. This is at the tip top of my dexterity (retired, in my dotage, and so on) but I lose tracking often, missing many shots.

I wonder if anyone has experience (or could share a conjecture) on what I would experience if I swapped out the 100-400+1.4tc for the 150-600. I suspect that the new lens will be, maybe, a hair better optically and will have similar low light performance. I also suspect that autofocus will be generally better, I'm wondering if improvements would be worth the expense.

Hi Mark,

With an X-T3 so very similar AF system to yours, the 100-400 with and without the 1.4x TC is great for portraits.  When it comes to birds in flight, the 100-400 is great yet add the 1.4x TC and tracking is not very good.  I recommend keeping the TC off for BIF and cropping as you get consistently better results.

I used the Sigma 150-600 C for Canon with a Fringer adapter and AF and tracking were great.  Even when I used the Fuji 1.4x TC with this combination.

I've tried the XF 150-600 on an X-H2S in an exabit hall and I was on the second floor balcony where I was able to shoot down to the first floor as well as across the balcony.   My subjects were people walking which is easier than BIF and the combination tracked well except when the people were in the shadows in light levels similar to what one would have just after sunset.  In this case about 1/2 the time the combination failed to track people walking.  This was with pre production firmware and I don't know if it's a firmware issue or if the f8 maximum aperture of the XF-150-600 was causing the body to struggle.  If you are interested in this lens, I suggest you wait a bit and see what people think when there out in the field.

My X-T3 dose a fine job at birds in flight and suspect your X-S10 can as well.  This is a very difficult subject that takes most people years to master.

Morris