I might change the spec later, but I tried making screenshots literally about taking photos 📸
When you switch into photo-shooting mode, every control turns into operating a virtual camera—like handling a fly-cam—and you can no longer move your own avatar.
The angle of view and the aperture are provided as lenses, and since a prime lens can’t zoom, you move the virtual camera around to decide the composition and take the shot.
A zoomable lens can zoom within that lens’s available range from the virtual camera’s position, and in that case the field of view and so on change accordingly.
Changing the aperture alters how much bokeh you get, and at the same time the starburst of the lens flare changes—the more you stop down, the sharper the starburst becomes. You can also set things like the number of aperture blades, so the look of the starbursts and ghosting changes accordingly as well.
When you set focus with Shift + left-click, a green focus frame appears.

I’m not sure whether this approach is actually easy to use, but once the viewer is finished I’d like to go out and take some photos and judge again ❗️