LENS DIRT - IMPLEMENTATION
There is some free Lens Dirt stock footage available. Nonetheless, custom patterns could be made using a Noise Node along with a RotoPaint, for example.
- ActionVFX: https://www.actionvfx.com/collections/free-lens-dirt-overlays
- As well as in Josh Parks' CompositingPro: https://www.compositingpro.com/free-lens-dirt
There can be different ways to implement this based on context, here I provide a simple one:
The key takeaways would be:
- It is usually very out of focus, by being too close to the camera/sensor.
- It's recommended to keep it extremely subtle.
- A desaturated version is multiplied by a heavily blurred background to impress the color from it and to keep it just in the highlight. Feel free to grade the background prior to the blur to isolate just the highlights, as this effect should be just visible pretty much around them.
- Use a 'screen' merge operation to avoid values resulting above 1.
- More complex artefacts such as scratches can be simulated by the use of displacements on the background.