Investigate HSS/Auto FP flash behavior in Photography Mode

[erik-sutton95]

Goal

Investigate high-speed sync (Nikon Auto FP HSS) behavior in OpenZCine Photography Mode and make remote capture preserve, expose, and validate compatible flash operation.

Feedback

A photographer requested HSS synchronization with their flash while using OpenZCine.

Reddit source

Important scope distinction

The phone should not attempt to generate frame-accurate flash timing over Wi‑Fi or USB. HSS timing belongs to the camera and a compatible hot-shoe flash or radio trigger. OpenZCine’s role is to:

• avoid breaking an HSS configuration when it connects or triggers the shutter;
• expose and control camera-authoritative flash settings where Nikon’s remote protocol supports them;
• report compatibility, readiness, and failures truthfully;
• validate that app-triggered capture behaves the same as the physical shutter.

Proposed investigation

• Determine which supported Nikon Z bodies expose flash sync speed, Auto FP enablement, flash mode/control mode, flash compensation, flash-ready state, and attached-flash information over each transport.
• Test whether remote still capture fires a configured on-camera flash and common hot-shoe/radio triggers at ordinary sync speeds and in Auto FP HSS.
• Identify camera modes that disable or constrain flash, including electronic shutter/silent modes, incompatible drive modes, bracketing, shutter types, and active video settings.
• Test recycle-time behavior so bursts, interval capture, or rapid taps cannot silently produce unlit frames.
• Build a body/firmware/flash-or-trigger compatibility matrix rather than assuming every third-party system behaves identically.

Proposed experience

• Show the camera’s current flash mode, sync setting, HSS/FP state, compensation, and readiness when authoritative data is available.
• Warn when the selected shutter mode/speed or camera configuration prevents flash/HSS.
• Allow safe supported camera-side flash settings to be changed only after capability discovery and confirmed readback.
• Keep unsupported third-party flash controls on the flash/trigger itself; do not display speculative controls.
• Ensure remote shutter, self-timer, bulb/time, and timelapse flows wait for or clearly ignore flash readiness according to an explicit operator choice.

Success looks like

With a compatible Nikon Z body and HSS-capable flash or trigger configured for Auto FP, an operator can trigger a still from OpenZCine above normal sync speed and receive the same correctly synchronized result as pressing the camera shutter, with truthful HSS and readiness status in the app.

Open questions

• Is the request specifically for preserving camera/hot-shoe HSS, controlling Nikon CLS/AWL, or integrating a third-party radio-flash ecosystem?
• Which flash properties and readiness events are exposed through Nikon PTP/IP and USB?
• Does remote capture differ from a physical half-press/full-press sequence for flash metering or readiness?
• Which current Z bodies support Auto FP and at what maximum shutter speeds?
• Should third-party flash SDK integrations be considered separately after camera-native behavior is reliable?

Nikon references

• Nikon Auto FP high-speed sync and flash sync speed
• Nikon compatible flash features, including Auto FP