Lens
Barrel distortion, colour fringing and soft corners
What a real lens does to a picture: straight lines bow outwards, colour fringes appear in the corners and nowhere in the middle, and the corners lose both light and sharpness. Set distortion below zero for the pincushion a long lens gives you instead.
Rendering cost: medium. A few dozen samples per pixel: comfortable fullscreen on a discrete GPU, but cap the pixel ratio for a retina hero. How to tune it
Take Lens with you.
Lens is free. Sign in and it is yours — the background itself, with your settings already saved in, ready to drop into your site. The account is only somewhere to put the files. No card now, and no card later.
The other 61 come with a licence, $9.99 once.
$0forever
Your preset is in the URL. It survives the trip.