Fujifilm GFX100S/100 FOCUS BKT Feature still has can’t-reach-infinity-focus Bug dating back to 2019 (FOCUS BKT feature)

2021-05-09 • SEND FEEDBACK |
Related: focus stacking, Fujifilm, Fujifilm GFX100S, Fujifilm medium format, Fujifilm mirrorless, medium format

Update: see Fujifilm GFX100S/100 FOCUS BKT: Workaround for Failure to Reach Infinity Focus for a potential workaround.

Jim Kasson has confirmed the continuing existence of a bug that I reported back in August 2019.

I don’t have any lenses longer than 50mm, so I have no means to test longer focal length lenses at present. However,testing the Fujifilm GFX100S with the Fujifilm GF 50/3.5 , it is reaching infinity, so I don’t think this issue will be of concern for 63mm and shorter focals.

But even when the bug was clearly there, I never had issues with shorter focal lengths (63mm and shorter) more than one frame too few, so long as I was always careful to shoot one frame after the camera had done its job. And often I didn’t need to.

UPDATE May 30: for how well the FOCUS BKT = Auto feature works to avoid this issue, see Fujifilm GFX100S Focus BKT 'Auto' Mode: Usage and Example.

Information to review

Back then, I how the Fujifilm GFX100 FOCUS_BKT would abort the focus stepping sequence short of infinity. For lenses 110mm on up, it would stop grossly short (3 to 10 frames too early). For shorter lenses, generally 1 frame too early.

These pages are still highly relevant nearly two years later:

Fujifilm GFX100: Bug and Issues with the FOCUS BKT Feature, How to Mitigate

Fujifilm GFX100: Using the FOCUS BKT Feature for Focus Stacked Images

Those pages show examples and discuss mitigation strategies, including a simple fix for shorter focal lengths. There really isn’t any hope for 110mm on up, because too many frames are never taken by the FOCUS BKT feature.

Shame on Fujifilm for not fixing a bug that should never had made it into shipping firmware. At this point, it should be a red-faced embarrassment to both the engineering team and the quality assurance team, both prima facie incompetent to do even basic feature validation.