Filters are nodes that process an input to create a modified, "filtered" output, in a way you might be used to from other well-known imaging applications. The big difference with Material Filters is that they only work on one (sometimes more) inputs that do not represent a full material.

Filters are one of the most used major categories. Apart from the Atomic nodes category, no other category is as useful when building textures from scratch. Take the time to get to know each of the subcategories:

• Adjustments
  Expanded color, tone and value adjustments.
• Blending
  Advanced and expanded blending modes.
• Blurs
  Advanced, high-quality blurs.
• Channels
  Expanded Channel-mixing nodes.
• Effects
  Texturing-oriented image effects, as well as "Layer Style"-type effects.
• Normal Map
  Normal Map focused operations.
• Tiling
  Nodes focused on fixing and improving tiling.
• Transforms
  Advanced (mathematical) 2D-space transformation operations.