1. SHUTTERThe A9 III has a global shutter sensor (all the pixels are read simultaneously). There are no mechanical curtains. The A1 features a rolling shutter sensor (pixels are read one row at a time) with 2 options: full electronic shutter and EFCS.
2. SPEEDThe A1 can operate at 30fps (Compressed RAW or JPG) with AF and AE tracking.The A9 III takes speed to a new level, reaching 120fps with JPG, Compressed RAW, AF/AE tracking.
3. FLASHThe A9 III can shoot up to 1/80,000s, and can sync that shutter speed with flash too, without the need for HSS.The A1 can sync up to 1/400s (1/500s in APS-C), or 1/8000s with HSS.
4. VIDEOThe A1 can record 8K 30p with oversampling, and 4K 120p with pixel binning and a 1.13x sensor crop.The A9 III does 4K 60p (oversampling), and 4K 120p (pixel binning), with no crop at 100/120p.
5. PIXEL SHIFT The A1 can capture 16 images while moving the sensor slightly between frames, allowing you to create a 200MP file!The A9 III can composite 32 RAW images to reduce noise, and works handheld.