Autofocus System

The A6400 features one of the most advanced autofocus systems in its class, with 425 phase-detection points covering 84% of the frame and world-class Eye AF capabilities.

AF System Overview

The Sony A6400 delivers exceptional autofocus performance with its hybrid AF system combining 425 phase-detection points with 425 contrast-detection points. This enables incredibly fast acquisition times of just 0.02 seconds—among the fastest in the world for APS-C cameras.

Real-time Eye AF

Automatically detects and tracks eyes for portraits. Works for humans and animals.

Real-time Tracking

AI-powered subject tracking that maintains focus on moving subjects.

Flexible Spot

Manually position a focus point anywhere in the frame with adjustable size.

AF-C Continuous

Continuously adjusts focus for moving subjects. Essential for action and wildlife.

Real-time Eye AF

Real-time Eye AF is one of the A6400's standout features. The camera uses AI-based subject recognition to detect and track eyes with remarkable accuracy, even when subjects are moving, turning away, or partially obscured.

Human Eye AF

Detects eyes even when small in frame
Tracks through head turns and movement
Works with glasses and sunglasses
Select left or right eye preference

Animal Eye AF

Optimized for cats, dogs, and other animals
Works in both stills and video modes
Handles rapid movement effectively
Best results with eyes clearly visible

Eye AF Settings

Setting	Location	Recommended	Notes
Eye AF	Camera Settings 1 → AF2	On	Enable for automatic eye detection
Subject Detection	Camera Settings 1 → AF2	Human / Animal	Choose based on your subject
AF Track Sens	Camera Settings 1 → AF3	3 (Standard)	Adjust for sticky or responsive tracking
Sw. V/H AF Area	Camera Settings 1 → AF3	AF Point Only	Remembers separate AF points for orientations

Half-Press Activation

By default, Eye AF activates with a half-press of the shutter. For faster access, assign "Eye AF" to a custom button so you can activate it independently of focusing.

Tracking & Lock-on AF

Real-time Tracking uses Sony's AI-based subject recognition to follow subjects across the frame. Simply place your focus point on the subject and the camera will intelligently track it, even as it moves erratically or is temporarily obscured.

How to Use Real-time Tracking

1Set Focus Area to "Tracking" in Camera Settings 1 → AF1
2Position the tracking frame over your subject using the control wheel or touchscreen
3Half-press shutter to begin tracking—the frame will turn green when locked
4The camera will automatically switch to Eye AF when eyes are detected

Touch Tracking

Enable touch tracking by setting "Touch Focus" to "Touch Tracking" in Camera Settings 2 → Custom Operation2. Tap any subject on the LCD to begin tracking instantly.

Focus Area Modes

The A6400 offers multiple focus area modes to suit different shooting scenarios. Understanding when to use each mode will dramatically improve your hit rate.

Wide

Uses all 425 AF points. Ideal for Eye AF and general shooting where the camera selects the best focus point automatically.

Zone

Focus on a movable zone within the frame. Great for sports and wildlife where subjects move predictably within an area.

Flexible Spot

Precise point selection with Small, Medium, or Large spot sizes. Perfect for still subjects and creative compositions.

Expand Flexible Spot

Uses surrounding AF points to assist if the primary point loses focus. Balances precision with reliability.

Focus Area Quick Reference

Setting	Location	Recommended	Notes
Focus Area	Camera Settings 1 → AF1	Wide / Zone	Wide for Eye AF, Zone for specific areas
Focus Mode	Camera Settings 1 → AF1	AF-C	Continuous AF for moving subjects
Priority Set in AF-C	Camera Settings 1 → AF1	Balanced	Balanced emphasis on focus and release

Recommended Settings

Here are optimized settings for common shooting scenarios. Adjust these based on your specific needs and shooting style.

Portrait Photography

Focus ModeAF-C

Focus AreaWide

Subject DetectionHuman

Eye AFOn

Action & Sports

Focus ModeAF-C

Focus AreaZone / Tracking

AF Track Sens4 or 5 (Responsive)

Drive ModeContinuous Hi+

Wildlife & Pets

Focus ModeAF-C

Focus AreaWide

Subject DetectionAnimal

Eye AFOn

Street Photography

Focus ModeAF-C or AF-A

Focus AreaFlexible Spot M

Pre-AFOn

AF w/ ShutterOn

Troubleshooting

Eye AF Not Detecting Eyes?

Ensure Subject Detection is set correctly (Human or Animal). Eye AF works best when the subject is facing the camera and eyes are clearly visible. In low light, consider using a larger aperture or higher ISO to help the AF system.

Focus Hunting in Low Light

Enable AF Illuminator (Camera Settings 1 → AF4) to assist focusing in dark conditions. For video, use AF Drive Speed set to "Slow" to reduce hunting during continuous autofocus.

Tracking Loses Subject

Try adjusting AF Track Sensitivity. Use a lower value (1-2) for subjects that pause frequently, or higher values (4-5) for erratic movement. Touch Tracking can also help with initial subject selection.