Other: Sigma vs Sony 1.4 E mt primes for AF

[LennyLevy]

Has anyone compared the Sigma 85mm & 50mm f1.4 E mt ART lenses as compared to the Sony's for use on the new Sony AF cameras like the FX9, A7siii, FX6 etc.

The 85 in particular has gotten great reviews and they are noticeably cheaper. I'm concerned mainly about how good their AF will be compared to the Sonys.

 

[ahalpert]

I haven't used those primes, but my experience with the Sigma 24-70 compares favorably to the Sony zooms I have (12-24 f/4, 28-135).

Dustin Abbott's review speaks glowingly of the AF performance on the Sigma 85 1.4 FE -

Sigma has utilized a stepping motor on this lens for smooth, fast, and quiet operation. This appears to be fastest-focusing 85mm F1.4 lens on Sony and definitely has an edge on the GM lens in overall performance. It’s quieter and smoother (and the GM has a somewhat “gritty” sound and feel at times). The focus motor of the 85DN is extremely quiet and is only audible with your ear pressed against the barrel. It is quiet enough that the on-board mic does not pick up any focus sounds during video focus or when doing focus pulls. Good news there.

The focus motor is also nicely smooth when doing focus pulls.

Focus speed in AF-C mode is nice and fast, with typical focus changes being near instant and with no drama. Right out of the box I was seeing focus nailed on all my shots. Pet Eye AF grabbed on perfectly in this shot.

https://dustinabbott.net/2020/08/sigma-85mm-f1-4-dn-art-review/

I'm sure he has similar details in his review of the 50 ART.

I will say that the footage I looked at from the Sigma 35 f/1.2 was very bad for autofocus in video because you can see the motor stepping through its range at intervals. But the Sony 50 f/1.2 has more motors and seems to focus more smoothly.