Altus Dual – Slowest (renders the frame twice before denoising) and non-interactive but produces great results for final quality renders.Altust Single – Slower (renders the frame once before denoising) and non-interactive but produces good results for final quality renders.OptiX – Very fast and can be used during interactive rendering but can have more trouble cleaning noise compared to alternatives.Redshift has three built-in Denoising Engines and they can easily be switched between here, each one with their own general pros and cons.
Denoising can only do so much and a balance must be struck between Bucket Quality and the denoiser engine of choice in order to find what works best for your project. Denoising allows you to easily render images at a reduced baseline quality (lower sample counts) and increased speed at the expense of some potential accuracy. The Denoising checkbox allows you to quickly toggle denoising on and off.