Photon Shader

Fully revamped sky, lighting and water
Multiple volumetric cloud layers driven by an immersive weather system, providing different skies each day
Colored lighting (enabled with Ultra profile, requires Iris)
Full labPBR resource pack support
Extensive settings menu allowing you to customize every aspect of the shader, including many optional features like Minecraft-style clouds and a galaxy in the night sky
Volumetric fog
Lighting effects: variable-penumbra shadows, ambient occlusion, screen-space reflections
Camera effects: bloom, depth of field, motion blur
Much improved image quality with TAA, FXAA and CAS
Advanced temporal upscaling (disabled by default) for low end devices

Photon can be used with Iris (recommended) or OptiFine on Nvidia, AMD and Intel GPUs
Iris is a modern shader loader with far better performance, mod compatibility and developer features than OptiFine. Some features (Colored Lighting) will only work on Iris
Photon is also compatible with Distant Horizons

Emin - Shadow bias method from Complementary Reimagined (fully fixes peter panning and light leaking underground!)
DrDesten - Depth tolerance calculation for SSR (helps to prevent false reflections)
Jessie - f0 and f82 values for labPBR hardcoded metals
Sledgehammer Games - Bloom downsampling method used in Call of Duty Advanced Warfare (described here)
http://momentsingraphics.de/ - Blue noise texture
NASA Scientific Visualization Studio - Galaxy image

Compatibility