- Ed Dozier
The Nikon Z9 with Teleconverters: No Focus Speed Penalty?
I had to perform this test comparison several times, because I could hardly believe my eyes. The Nikon Z9 focuses some lenses just as quickly with my teleconverter attached as it does without!
I am using my Sigma TC-1401 1.4X teleconverter with both my Nikkor 500mm f/5.6 PF and my Sigma 70-200 f/2.8 Sport lens.
Nikon Z9 with the Sigma TC-1401 1.4X teleconverter
The shot above shows the Z9 with both the FTZ-II and Sigma 1.4X teleconverter attached to my 500mm f/5.6 PF lens. This is one of the combinations I used to measure focus speed.
With the DSLRs that I have tried, attaching this teleconverter will slow down focus speed by about 25%. The 1-stop lesser light level always gives you a speed penalty, in addition to the resolution drop.
I used 120 fps video to record the focus scale motion on my lenses in bright light. I just have to count the frames that show the focus scale motion to measure the focus speed.
When I did this test to see how much my teleconverter would slow down the focus time on my 500mm PF, I found no difference when using the Nikon Z9! How can this be?
The Nikon Z9 shoots with the requested lens aperture, down through f/5.6. It never opens up the aperture while shooting. Any DSLR will focus with the lens at its widest aperture, and then quickly stop down the aperture to take the shot. DSLRs need all the light they can get to focus quickly. The Nikon Z9 can focus in dim light, and it doesn’t need the lens aperture to be wide open.
The 500mm Test
Without using a teleconverter, I focused the 500mm PF with the Z9 in sunlight. I started with the lens on minimum focus distance, and focused on a distant tree using the “3D-Tracking” focus mode. I recorded the focus scale using video at 120 fps. I counted 41 frames that showed focus scale motion, or 0.342 seconds.
I repeated the test (several times!) with the Sigma 1.4X teleconverter attached, and again recorded typically 41 frames of focus activity going from minimuim focus to infinity (0.342 seconds). No change in focus speed when I include the teleconverter!
When I did focus speed tests using my D500 DSLR and this same lens, it could focus in 0.308 seconds without using the teleconverter, but it took 0.400 seconds when I attached the teleconverter.
The Sigma 70-200mm f/2.8 Sport Test
Still using 3D-tracking for focus, my testing found the following:
No teleconverter at 200mm, f/4: 49 frames, or 0.408 seconds.
With teleconverter 280mm, f/4: 53 frames, or 0.442 seconds.
I also tried wide open at f/2.8, 200mm with no measured focus speed change. In all of my tests, I went from minimum focus (about 4 feet) to infinity. This is a much longer range than the 500mm PF lens, which I think accounts for the longer focus time.
Similar to the 500mm results, my D500 was faster-focusing than the Z9 without the teleconverter (0.36 seconds) but slower than the Z9 with the teleconverter (0.45 seconds). Again, you couldn’t perceive this slight difference with the naked eye.
This is only about an 8% slowdown using the Z9, compared to a 25% slowdown on my D500 camera. This speed change can’t be noticed in use; there’s essentially no focus-speed penalty here, either!
I also noticed that my Z9 really reduced focus-hunting when using the 500mm/TC combination in dim lighting, compared to either the Nikon D850 or D500 cameras. Focus of course gets slower in really dim light with the Z9, but it retains fantastic focus precision.
Due to the extra focus accuracy and repeatability, my shots are nearly always a tiny bit sharper when using the Z9/TC combination compared to my DSLRs. I haven’t even had to perform any focus fine-tune calibration with the Z9.
Expect similar results to the Sigma TC-1401 when using the Nikon teleconverters.
I think that the Z9 is just showing off. I had held off for a long time getting a mirrorless camera. I wanted nothing to do with short battery life, poor viewfinder frame refresh rates, low viewfinder resolution, substandard low-light performance, and slow focus. Those days thankfully are now over.