Sigma 16mm f/5.6 AF problem

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Kogel Forum Member • Posts: 98
Sigma 16mm f/5.6 AF problem

I wanted to find the optimum aperture. Camera on tripod, 2s timer, AF-S, expand flexible spot AF to a distant object.

Used jpeg-file size to rate sharpness, 100% is the largest file (in this test larger f-numbers will perform better due to deep DOF)

Test 1: increase f-number (f/1.4 -> f/16)

Test 2: different scene, reduce f-number (f/16 -> f/1.4)

At f/5.6 (and f/5.0) performance drops significantly, because the photos are out of focus (too near, distant objects do not get sharp, near objects are very sharp)

There seem to be some AF-related issues with this lens on Sony cameras, however I didn't manage to find out what causes the problems and how to fix them. Does anyone experience similar problems?

Sony ILCE-6500 v1.06

Lens Firmware 01

Aperture priority



AF-S. Priority: AF

Focus: expand flexible spot, large

Pre-AF: off

Face detection: on

Silent Shooting: off

Steady Shot: on


 Kogel's gear list:Kogel's gear list
Sony a6500 Sony E 10-18mm F4 OSS Sony E 16-50mm F3.5-5.6 PZ OSS Samyang 12mm F2.0 NCS CS Sigma 30mm F1.4 for Sony E +4 more
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