JUST FIX IT IN POST?
Published by Dustin Valkema from PRO EDU
When compositing render layers, there can be problems worth solving during post-production rather than in your 3D software.
Fireflies are one of those artifacts that we get from time to time with 3D rendering. They can be a pain when working with motion, but it's an easy fix in still renders during post-production in Photoshop. Fireflies happen when the rendering software struggles to resolve samples in given areas. This is most common in high contrast near light blowouts or when working with various reflective surfaces in your scene. Though most denoisers and or higher samples can usually fix this, finding the exact solutions in 3D can be time suck at times. Sometimes it's worth "fixing in post."
In the video, Dustin Valkema runs through solving this issue quickly using Photoshop's "Dust And Scratches" filter. We'll run you through the procedure below.
Notice the fireflies in the example below? The white-hot pixels on the ground of our render.
1) Create a "stamp visible" layer of your entire composite. Press CTRL+ALT+SHIFT+E on a pc, or CMDS+OPTION+SHIFT+E on a PC. This creates a new layer on top of your composite from all visible layers.
2) Right-click the stamped layer and convert it to a "smart object." We do this so that we can manipulate our adjustments of the filter layer if needed.
3) Head up to the "filters menu," down to noise, and click "Dust and Scratches." See image below
4) Start with a radius of 1 pixel and adjust your threshold slider until your fireflies are removed. With the threshold slider, values to the left will be the full effect. As you're stepping up your threshold, you may need to set your pixels to a slightly higher value to thoroughly remove the artifacts. These values will vary from image to image; keep that in mind. When you're satisfied with the result, click OK.
5) With the smart filter now applied to the smart object, create a layer mask while pressing ALT on a PC or OPTION on a Mac. This will create a black layer mask, allowing you to paint with a white brush to reveal the firefly removal effects locally vs. the entire image. This is an excellent habit to get into as the "Dust And Scratches" filter can often destroy details, as seen in the video.
This process can often be repeated over various layers to solve multiple problematic areas that vary in scale. Though it's excellent for fireflies, it also helps with tricky grain artifacts, especially when rendering a heavy depth of field.
Hopefully, this quick tip helps those in need of a fast solution to what could be a very time-consuming problem otherwise.