Sony A9 focus accuracy – birds in flight hit rate
If you would rather head straight to a concise summary, the TL;DR is at the foot of the page — or jump directly to the FAQ.
In this post I make a lens speed and noise comparison between the EM1x and the A9 across the whole range of lenses that a professional or high-level amateur might use, including matched pairs of images from each camera at a range of ISO levels so that you can see for yourself what the differences are.
In an earlier post, I did a noise comparison between the Sony A9 and the Olympus EM1x cameras when used for birds in flight. The analysis compared the the EM1x with the Olympus pro telephoto lenses to the A9 with the Sony 200-600 f5.6-6.3 lens, and showed that there was no practical difference in noise between the two systems when used at the higher ISOs frequently necessary for birds in flight. However birds in flight is a fairly narrow use case. So lets look at the complete range
TL;DR
- Sony A9 focus accuracy for birds in flight varies dramatically by shooting conditions: 72% in predictable, calm scenarios but only 39% in rapid-reaction situations.
- The A9’s linear PDAF sensor excels at detecting vertical contrast (feather patterns) but struggles with horizontal contrast (wing profiles), unlike Olympus cross-type sensors.
- Focus acquisition speed is critical: the Sony 200–600 lens (single motor) is slower than the Olympus 300mm f/4 (faster focus motor and lighter lens).
- System inertia matters: Sony A9 + 200–600 (2.1 kg) vs Olympus EM1x + 300mm (1.3 kg)—tracking erratic birds requires nimble equipment.
- Noise performance is comparable at high ISOs, but the Olympus system is significantly lighter and more ergonomic for all-day shooting.
Frequently asked questions
Why does the A9 achieve only 39% accuracy in rapid-reaction shots?
The Sony 200–600 lens has a single focus motor (slower acquisition) and the A9’s linear PDAF struggles with horizontal contrast. In 1–3 second windows where there’s no time for servo recovery, the system can’t lock focus quickly enough on erratically moving birds.
What equipment do I need for reliable bird photography?
Quality telephoto lenses (300mm f/4 or longer full-frame equivalent), a camera with fast autofocus and cross-type PDAF sensors, and image stabilization. The Olympus system with Pro telephoto lenses excels in weight, weather sealing, and AF arrays.
How do camera systems compare for birds in flight?
Olympus EM1x advantages: omni-directional cross-type PDAF (detects all contrast equally), lighter system (1.3 kg lens vs 2.1 kg Sony), faster focus motor, better ergonomics for tracking. Sony A9 advantages: larger sensor, more autofocus points (693 PDAF vs Olympus’s fewer), excellent in calm/predictable conditions.
What are the key focus techniques for birds in flight?
Use continuous autofocus with bird tracking, shoot at high frame rates (15+ fps), use Pro Capture to buffer pre- and post-press frames (eliminates reaction-time lag), and set a small focus area (5×5 grid for distant subjects) rather than all-points mode.
How important is noise performance?
Noise is manageable at high ISOs with modern cameras and fast lenses. The effective system noise depends on both sensor and lens speed, not sensor alone. Sony and Olympus are comparable; weight and ergonomics matter more for all-day BIF shooting.
