Mirrorless Behavior Under Continuous Autofocus (X-T3, but cross-brand question)

[ejkrouse]

Due to increased requests for video (and a little bit of curiosity I suppose), I recently made the switch from Nikon DSLR equipment to Fuji, with an X-T3 and 16-55. It's an excellent combo for general still and video work, and has quickly paid for itself with new opportunities. I've had the same "wow that's sharp!" reaction with it as previously felt when I first shot with the Sigma 18-35. I'd buy it all over again just for the blissful electronic shutter silence while capturing timelapses.

My issue with the X-T3, after 5 months of shooting, is how the camera stops the lens down to my selected aperture while focusing in Continuous Mode. I'm a full-time dog photographer, specifically niched down to indoor studio portraits under strobes. AF-S is fine most of the time, and the camera doesn't stop down in AF-S but AF-C would be a godsend to use with high energy subjects. If my preset is 1/250 and f/11, and I half press or attempt back button focus, the camera hunts like crazy while trying to squint through such a small aperture. Reviewing my last session, I'd estimate roughly 30% were out of focus when set to AF-C. Maddening.

My question; is this a Fuji thing, or do all mirrorless cameras have the same behavior of stopping down under continuous autofocus possibly due to On-Sensor Phase Detect?

I'm very fond of the Fuji system and how it just gets out of the way, but if this is a persistent issue, I'll be shopping for a studio specific DSLR.

Thanks for your help!

[rdonson]

AF-C really should be set up using the "AFC Custom Settings" for best results.  Which setting are you using? 

I use AF-C custom settings with great results for sports. 

AF-C settings
1 - Multi purpose
2 - Ignore obstacles & continue to track subject
3 - For accelerating/decelerating subject
4 - Suddenly appearing subject
5 - For erratically moving and accelerating/decelerating subject
6 - Custom

With each setting you can modify
- Tracking sensitivity
- Speed tracking sensitivity
- Zone area switching 


Sorry.... I missed the real issue "My issue with the X-T3, after 5 months of shooting, is how the camera stops the lens down to my selected aperture while focusing in Continuous Mode"

I'll think on this a bit more.  I don't shoot much video.

[ejkrouse]

Good morning and thank you for the reply/recommendations. I spent the first week or so with the X-T3 futzing with AF-C settings in both still and video modes, and it works beautifully outside. My issue (again, apologies for burying the lede with my ramble) is, when set to AF-C and autofocus engaged (e.g. half-press), the lens will close down to my set aperture, just as if I hit the DoF preview button. The EVF compensates somewhat, but I can hear the aperture close down, and the focus accuracy/ability goes out the window.  Continuous AF under just modeling lights at f8 is rendered unworkable. I'm curious to see if this is a behavior seen across mirrorless platforms (Sony, Nikon Z, etc). If so DSLR may be the way to go for that specific application. I have always wanted to try a D850, and have a bag of Nikon glass still...

Thanks again for the insights, all. 

[rdonson]

Have you manually set ISO and shutter speed???

[ejkrouse]

Yes, manual everything save for AF.

[chez]

Sony used to do the same but fixed the issue with a firmware update. If you turn Live View off, the camera will open up to largest aperture while focusing...then stop down while taking photo. If Live View is on, the focus occurs at whatever aperture is selected.

So you have a choice whether to focus opened up or stopped down.

[ejkrouse]

Interesting. Here's hoping for a Fuji update then!

[rdonson]

You could call Fuji support and share your experiences.  They've been VERY helpful for me and pleasant to deal with.

Is your X-T3 and 16-55 at the most recent firmware levels?

[ejkrouse]

Thank you Ron, I'll give them a ring. My X-T3 and 16-55 are at the most recent firmware.  I'll report back if I glean any info.

[rdonson]

Best of luck.  I look forward to knowing what they tell you.

[ejkrouse]

Just got off the phone with Fuji; very nice and helpful folks, who went through all settings on their cameras while walking me through, and when they got stumped, a higher level tech was brought in. I tested myself on two different X-T3's and two lenses, 16-55 and 18-55, so 4 scenarios. Per Fuji, the darkening/stopping down on AF-C is considered as normal operation, and they suggested enabling Pre-AF to give the camera a head start. I can't say this is an ideal situation for me, but at least I got to the bottom of it.

I'd love to hear from folks with Sony, Nikon Z, or Canon R systems about their experience. My test setup is lazy: reading level light (8footcandles, or 1/60 F/1.4, ISO800) static subject (my opened colorchecker passport on my desk), Single AF point set at lower left Rule of Thirds grid intersection. AF-C, then half press at maximum aperture, then minimum.

[chez]

I already indicated how Sony handles this. The behaviour can be controlled with a setting, thus allowing you to not have the lens stopped down during AF if that is what one wants. The reason they stop the lens down is to handle focus shift of some lenses. Fuji must have some lenses that have focus shift while stopping down.