Devlog #1: Long Exposures

A few weeks ago when i was on vacation, I was standing on a bridge at 1 am playing around with some long exposures on my dslr, and I realized that iphones don’t have real long exposures. Without a third party app, the closest that iPhones can get to long exposures is through converting live photos, which is very limited in what it can do.

live photos

Basically, live photos consist of the cover photo and a ~3 second video. I used photokit and avfoundation to extract raw pixel buffers from the video. I then used a metal compute shader to average the pixel values across all of the frames of the video together to make the long exposure. At this point i had basically reconstructed the built-in long exposure from apple.

long exposure editting

The big thing that I wanted to do was take these long exposures and edit the frames that went into them (what you can’t do on apple). This lets me make long exposures with fewer frames and lets me go around apple’s built-in long exposure limitations. To create this feature, I added a range slider to select what frames go into the long exposure (letting me choose the start and end frame)

library

I implemented a simple library feature that basically lets you save your long exposures into the app (and also into your photo library on your phone)

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I also started a frame alignment feature and an exposure modifier, but i’m still working on those so i’ll save it for another devlog

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I spent at least 10 more hours on this before i realized that i didn’t have hackatime connected to my xcode :(