The team behind the popular Halide app has launched its second app. Spectre uses computational imaging methods to simulate long-exposure photography on conventional cameras.

You can use the app to make moving subjects disappear in busy areas, such as the cars on the bridge below, or you can create light painting and other effects through subject motion, just like when shooting with a DSLR that has been set to a long shutter speed.

However, Spectre works in a different way, doing away with many of the limitations of a conventional long-exposure. There is no need to put the phone on a tripod or take a series of test exposures to find the shutter speed that works best.

Instead, the app uses machine learning and computer vision to create a computational shutter. Spectre doesn't capture a single frame at a long exposure but takes hundreds of frames during the exposure time and merges them. This means you not only get a still image as a final result but also a video.

Results are saved in Apple's Live Photos format which lets you make adjustments after capture, such as choosing a key frame or applying Live Photo effects.

The app uses scene recognition for optimized results. For example, frames captured of a beach scene might be merged for a smooth appearance of the water. A busy cityscape at night is processed for a pleasant rendering of light trails. Thanks to AI-powered image stabilization handheld long exposures of up to nine seconds are possible and during capture a stability indicator tells you if your hands are too shaky.

If you'd like to try long-exposure photography with the iPhone and Spectre, you can download the app on the App Store now for an introductory price of $1.99.