Dusklapse

Dusklapse is an app for creating day-to-night or night-to-day time-lapses (the so-called Holy Grail) using DSLR / DSLM cameras.

The app connects to your camera via Wi-Fi and adjusts your camera’s exposure time, aperture and ISO settings to pre-defined limits, enabling you to capture time-lapse footage with significant changes in light, such as from day to night or vice versa.

What it does

• Measures every frame. Each JPEG preview is decoded and reduced to one brightness number on a 0–10000 scale, where mid-grey sits near 5000. The measurement is a log-average of linear luminance, so a bright sky or a dark foreground does not drag it around the way an arithmetic mean would.
• Corrects the exposure between frames. When a frame falls below the reference, one dial moves by one notch - shutter first, then aperture, then ISO at sunset, and the reverse at sunrise. Each dial has its own limit and its own on/off switch.
• Follows the sky, optionally. Given a position and the time, Dusklapse works out where the sun is and walks the reference down as it sets, so night frames read as night rather than as an evenly lit day that happens to contain stars.
• Shows what it is doing. A histogram of the current frame, and charts of how the dials and the brightness have moved across the whole sequence.

What it does not do

Dusklapse does not release the shutter. Frame timing belongs to an external intervalometer, and the app only adjusts the exposure between frames. This is deliberate: an app that must stay awake and on schedule for two hours is a fragile thing to hang a night's work on.

It also never transfers RAW files. A frame's file type is checked before anything crosses the network, and only the JPEG is fetched - set the camera to RAW + Basic and the small JPEG becomes the preview while the RAW stays on the card.

What you need

• A camera that exposes its settings over Wi-Fi (see Cameras).
• An external intervalometer, or the camera's built-in one.
• An iPhone or iPad on the camera's Wi-Fi.

Cameras

Vendor	Protocol	Status
Nikon	PTP-IP	Works. Developed against a Z 6 in access-point mode.
Canon	CCAPI	Implemented, not yet verified against a body.
Sony	-	Not supported.
Mock	-	A simulated camera, for trying the app without hardware.

On Nikon bodies the camera must be in access-point mode - the one the menu calls connect to smart device. Station mode, where the camera joins an existing network, closes the connection as soon as the shutter fires.

Status

Dusklapse is early. It is distributed through TestFlight, the version numbers are still 0.1.x, and the parts that have run through a real sunset are the Nikon connection, the measurement and the ramp. Bug reports are welcome on GitHub.