Hackers Unlock Hidden Variable Shutter and BIG6 Features on the Sony A7S III

Your Sony A7S III can now run Variable Shutter and the BIG6 home screen, two features Sony never gave it. But there’s a catch: you need an unofficial hack, and there’s no public guide for it yet.

Reddit user CoupleMother1623 shared photos of the mod running on their camera. According to the poster, the whole thing took about two days, and they promise a step-by-step manual for later.

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What Is Variable Shutter?

Variable Shutter is a banding killer. It lets you fine-tune your shutter speed in tiny increments, so you can match it to the flicker of an LED light or screen.

If you’ve ever filmed a screen or shot under LED stage lights, you’ve probably met those dark bands across the frame. They appear because the light flickers during the exposure, and the usual shutter speed steps are too coarse to match it. Sony’s support guide says as much.

With Variable Shutter on, the speed shows up with a decimal, like 250.6 instead of 250. Once the shutter matches the flicker cycle, each frame gets consistent brightness and the bands disappear.

Sony already offers the feature on models like the ZV-E1 and even the ZV-E10 II. So the budget vlogging camera got the flicker fix, while the low-light video specialist often used in dark venues didn’t.

BIG6 is Sony’s cinema-style home screen. It shows frame rate, ISO, shutter, F-stop, LUT or look, and white balance at a glance. Sony built it for its CineAlta cameras, then brought it to the FX3 with firmware 7.00.

How the Hack Works

The mod doesn’t build these features from scratch. It unlocks what’s already there. According to CoupleMother1623, the camera has a hidden update channel that stays reachable over USB, even in normal Mass Storage mode. That channel lets the hack run custom code with full system access. The Variable Shutter and BIG6 screens already exist in the firmware, but they’re hidden on this model, so the hack flips the switches that keep them out of sight.

“No firmware is modified; a reboot erases everything,” the poster writes. There’s one exception: the camera’s settings memory can be written directly, and those changes stick. That makes the Variable Shutter setup permanent.

Should You Try It?

If your A7S III pays the bills, no. At least not yet. There’s no public manual, and the results come from individual owners rather than Sony or independent testing. Digital Camera World shares a cautionary tale from another Redditor: after he reverse-engineered Sony firmware to add shutter angle, he went for 8K on the A7 IV and bricked the camera, leaving it stuck in a boot loop.

Still, if you have a spare body, a sense of adventure, and a deep hatred of LED banding, keep an eye on that promised manual. Just don’t blame us if your A7S III turns into a very expensive paperweight.

[via Reddit]

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