🎬 Lesson 43: Compositor Basics

💡 Compositing Defined

Compositing is the process of combining and enhancing rendered images to create the final output.

In Blender, compositing involves:

• Post-processing renders: Adjusting colors, contrast, exposure after rendering
• Combining elements: Layering multiple renders, effects, or images
• Adding effects: Glows, blurs, lens flares, depth of field, motion blur
• Color grading: Setting mood and atmosphere through color
• Working with passes: Using render passes for maximum control
• Fixing issues: Correcting problems without re-rendering

The Node-Based Approach:

Blender's Compositor uses a node system similar to Shader Editor and Geometry Nodes. You connect nodes to build a processing pipeline. Each node performs a specific operation—color adjustment, blur, mix, etc. The final output node shows your result. This approach is:

• Visual: See your processing pipeline as a flowchart
• Flexible: Easy to rearrange, modify, or bypass steps
• Non-destructive: Original render unchanged, all adjustments are live
• Professional: Industry-standard approach (Nuke, After Effects use similar systems)

✅ Benefits of Compositing

1. Save Rendering Time

• Adjust colors, exposure without re-rendering (huge time saver!)
• Add effects that would take hours to render in 3D (glows, blurs)
• Experiment with different looks in seconds
• Example: Change sunset to midday lighting with color adjustment—no re-render!

2. Maximum Control

• Separate control over different elements (lights, shadows, reflections)
• Adjust specific objects without affecting others
• Fine-tune every aspect of the image
• Example: Make character brighter without changing background

3. Professional Effects

• Glows and glares for lights and emissive objects
• Atmospheric effects (fog, haze, god rays)
• Lens effects (distortion, chromatic aberration, vignette)
• Film grain and stylization
• These look better and render faster in post!

4. Color Grading and Mood

• Set emotional tone through color (warm=welcoming, cool=sterile)
• Match photography styles (cinematic, vintage, HDR)
• Ensure consistency across multiple renders
• The "film look" comes from compositing!

5. Fix Problems

• Too dark? Adjust exposure in comp instead of re-lighting and re-rendering
• Colors off? Color correct in seconds
• Need sharper image? Apply sharpening filter
• Spot fixes without touching 3D scene

🤔 The Decision Framework

General Rule: If it affects light simulation (shadows, reflections, indirect lighting), do it in 3D and re-render. If it's a post-process effect (color, blur, glow), do it in Compositor. When in doubt, try Compositor first—it's faster!

💡 Understanding the Workflow

Standard compositing workflow:

1. Render your scene
   • Get a good base render (proper lighting, materials)
   • Enable necessary render passes
   • Render at final resolution (or test at lower res)
2. Load render in Compositor
   • Switch to Compositing workspace
   • Enable "Use Nodes" and "Backdrop"
   • Render image automatically available
3. Color correction first
   • Fix exposure, contrast, white balance
   • Get the foundation right before adding effects
   • Think of this as your "develop the negative" stage
4. Add effects and enhancements
   • Glows, blurs, sharpening
   • Atmospheric effects
   • Each effect is a new set of nodes
5. Final polish
   • Vignette, film grain, lens effects
   • Final color grade and mood adjustment
   • The subtle touches that complete the look
6. Output final image
   • Viewer node shows result in Compositor
   • File Output node saves processed image
   • Or render again to bake compositing into final output

🎯 Ready to Transform Your Renders?

The Compositor is the secret weapon of professional 3D artists. It's where good becomes great, where renders become art. You're about to learn techniques that separate amateur work from professional results. The best part? Most of this is fast and fun—you'll see results immediately and can experiment freely. Let's dive into Blender's compositing workspace!

✅ Getting Started

Method 1: Switch to Compositing Workspace (Recommended)

1. Look at the top of Blender's window (workspace tabs)
2. Click "Compositing" workspace tab
3. Result: Automatically configured layout with:
   • Node Editor (Compositor) in main area
   • Image viewer at top
   • Properties panel on right
4. This is the fastest way to start compositing!

Method 2: Manual Setup (For Custom Layouts)

1. In any editor, click the editor type icon (top-left corner)
2. Select "Compositor" from the menu
3. Editor changes to Compositor node view
4. You may need to enable "Use Nodes"

First-Time Setup (Do This Once):

• In Compositor editor, check the box: "Use Nodes" (top header)
• Check the box: "Backdrop" (shows your image in background)
• You'll see two default nodes: "Render Layers" and "Composite"
• These checkboxes stay enabled once set!

💡 Understanding the Interface Components

1. Node Editor (Main Area)

• Purpose: Where you build your compositing node tree
• Navigation:
  • Middle Mouse = Pan view
  • Scroll = Zoom in/out
  • Ctrl + Tab = Zoom to fit selected nodes
  • Home = Frame all nodes
• Adding nodes: Shift + A (opens Add menu)
• Selecting: Click nodes, B for box select, A to select all
• Connecting: Click and drag from output socket to input socket

2. Backdrop (Background Image)

• Purpose: Shows your composited image directly in the node editor
• Enable: Check "Backdrop" in header (highly recommended!)
• Controls:
  • V = Toggle backdrop visibility
  • Alt + V = Fit backdrop to view
  • Can zoom backdrop independently from nodes
• Why it's great: See results live while building node tree!
• Shows output of: Any Viewer node you add

3. Header Bar (Top of Editor)

• Editor type icon: Switch editor types
• "Use Nodes" checkbox: Enable/disable node system
• "Backdrop" checkbox: Show/hide backdrop image
• View menu: Navigation and display options
• Select menu: Selection tools
• Add menu: Add new nodes (or Shift+A)
• Node menu: Node operations (duplicate, delete, etc.)

4. Sidebar (N Panel)

• Toggle: Press N to show/hide
• Item tab: Properties of selected node
• Tool tab: Various compositor tools
• View tab: View settings and annotations
• Most useful: Item tab for detailed node settings

✅ The Essential Node Set

Input Nodes (Where Images Come From):

Render Layers

• What it is: Brings your rendered image into Compositor
• Created by default when you enable Use Nodes
• Outputs: Image, Alpha, plus all render passes you enabled
• Scene/Layer selection: Choose which scene and view layer to use
• This is your starting point!

Image Node

• What it is: Load external images or image sequences
• Use for: Background plates, overlays, reference images
• Supports: JPG, PNG, EXR, image sequences, video files
• Add: Shift+A → Input → Image

Output Nodes (Where Results Go):

Composite

• What it is: The final output node (must have one!)
• Created by default when you enable Use Nodes
• Purpose: Whatever connects here becomes your final render
• When you render: The composited result saves to file
• This is your endpoint!

Viewer Node

• What it is: Preview node for checking intermediate results
• Purpose: See what's happening at any point in your node tree
• Shows in: Backdrop and Image Editor
• Usage: Connect any image output to Viewer to see it
• Shortcut: Select node, then Ctrl+Shift+Click to auto-add Viewer
• Pro tip: Use multiple Viewers to compare different stages!

File Output Node

• What it is: Save images to specific files/locations
• Use for: Saving intermediate results, different versions, passes
• Configure: File path, format (PNG, EXR, etc.)
• Power feature: Save multiple outputs from one render!

💡 Node Socket Types

In Compositor, sockets have colors indicating data type:

Yellow Sockets (Color/RGBA):

• Contains: Full color image data (Red, Green, Blue, Alpha)
• Most common type in Compositor
• Examples: Image output, Color input, final composited result
• 4 channels: RGB for color, A for transparency

Gray Sockets (Value):

• Contains: Single-channel grayscale data (0.0 to 1.0)
• Use for: Masks, factors, alpha channels, depth
• Examples: Mix factor, blur amount, mask data
• Can connect to: Yellow sockets (converts to grayscale)

Blue Sockets (Vector):

• Contains: Multi-dimensional data (X, Y, Z or RGB)
• Use for: Motion vectors, normals, coordinates
• Examples: Speed pass for motion blur, normal pass
• Less common in basic compositing

Connection Rules:

• Yellow to Yellow: Full color data passes through
• Gray to Gray: Value data passes through
• Gray to Yellow: Grayscale becomes RGB (same value in all channels)
• Yellow to Gray: RGB converts to grayscale (luminance calculation)
• One output, many inputs: Can connect one output to multiple input sockets
• One input, one connection: Only one connection per input (new replaces old)

✅ Speed Up Your Workflow

Pro Workflow Tip: Ctrl+Shift+Click on ANY node to instantly add a Viewer showing its output. This is the fastest way to check what any node is producing. Use it constantly while building!

💡 Mastering the Background Preview

The Backdrop is your real-time preview system. Here's how to use it effectively:

Basic Controls:

• Enable: Check "Backdrop" in header (do this first!)
• Toggle visibility: Press V to show/hide quickly
• Fit to view: Alt+V frames the backdrop image
• Zoom backdrop: Same as node view (scroll wheel)
• Pan backdrop: Middle mouse drag

What Appears in Backdrop:

• Output of any Viewer node you add
• If no Viewer: shows output of last-modified image node
• Default: Shows Render Layers output (your render)
• Switch views: Connect different nodes to Viewer

Backdrop Tips:

• Keep it visible: Always work with backdrop on (instant feedback!)
• Use Viewer nodes liberally: Check intermediate results constantly
• Compare before/after: Toggle node mute (M) to see difference
• Zoom in: Check details up close when adjusting
• Full view: Zoom out to see overall composition

Backdrop Overlays:

• In header: "Backdrop" dropdown menu has options
• Move: Drag backdrop around independently
• Fit: Alt+V or use menu option
• Zoom: Use mouse wheel (backdrop and nodes can have different zoom!)

🎯 Quick Start Exercise

Let's set up your Compositor properly and see it work!

1. Prepare a Simple Scene:
   • Default scene (cube, camera, light) is perfect
   • Or open any scene you've created before
   • Make sure you can render it (F12)
2. Render the Scene:
   • Press F12 or click Render → Render Image
   • Wait for render to complete
   • You'll see the rendered image
   • Don't close render window yet!
3. Switch to Compositing Workspace:
   • Click "Compositing" tab at the top
   • Layout changes to compositing setup
4. Enable Nodes:
   • In Compositor editor header, check "Use Nodes"
   • Check "Backdrop"
   • You'll see two nodes: Render Layers and Composite
5. See Your Render:
   • Your rendered image should appear in backdrop!
   • If not: Render again (F12) with Compositor open
   • The render flows through: Render Layers → Composite
6. Test a Simple Node:
   • Position cursor between the two nodes
   • Shift+A → Color → RGB Curves
   • Connect: Render Layers Image → RGB Curves Image
   • Connect: RGB Curves Image → Composite Image
   • Adjust RGB Curves (drag on curve)
   • Watch backdrop update in real-time!
7. Add a Viewer (Pro Move):
   • Ctrl+Shift+Click on RGB Curves node
   • Viewer node automatically added and connected
   • Backdrop now shows RGB Curves output
   • This is how you preview any node!

Congratulations! You've set up your first Compositor node tree and made a live adjustment. The power of compositing is now at your fingertips. Everything from here builds on this basic flow: Render → Process → Output.

🎓 Interface Mastered!

You now know your way around the Compositor interface! You understand the layout, the essential nodes, socket types, keyboard shortcuts, and the crucial Backdrop system. This foundation lets you work efficiently. The interface itself is simple—the power comes from the nodes you connect. Speaking of which, let's dive into render passes, which unlock the full potential of compositing!

💡 Breaking Down the Render

A render pass is a separate output containing specific information about the scene.

Think of a Rendered Image as:

• Combined result of many lighting components
• Direct lighting + indirect lighting + shadows + reflections + AO + emission + ...
• All baked together into one final image
• Problem: Can't adjust individual components after render

With Render Passes:

• Each component rendered separately
• You recombine them in Compositor
• Advantage: Adjust each component independently!
• Example: Make shadows 30% lighter without re-rendering

Common Render Passes:

• Combined: The normal render (all passes mixed together)
• Diffuse: Base color without lighting
• Specular: Shiny reflections from lights
• Transmission: Light passing through transparent objects
• Emission: Light emitted from glowing materials
• Environment: Reflections from environment (HDRI)
• Shadow: Shadow information
• AO (Ambient Occlusion): Contact shadows in crevices
• And many more!

✅ How to Enable Passes (Cycles)

Location: Properties Panel → View Layer Properties (icon looks like stacked layers)

1. Find View Layer Properties:
   • Right side panel in default layout
   • Icon: Two stacked rectangles
   • Click to open View Layer settings
2. Scroll to "Passes" section:
   • You'll see checkboxes for different pass types
   • Organized by category (Data, Light, etc.)
3. Enable passes you want:
   • Check boxes next to desired passes
   • Each enabled pass adds to render time slightly
   • Only enable what you'll actually use
4. Render with passes enabled:
   • Next render includes all enabled passes
   • Available in Compositor from Render Layers node

Important Note: Passes are Cycles-specific. Eevee has different pass options (fewer available). For this lesson, we focus on Cycles passes as they're more comprehensive and industry-standard.

💡 The Most Useful Passes

Data Passes (Geometric Information):

Z (Depth):

• Contains: Distance from camera to each pixel
• Appears as: Grayscale (white=close, black=far)
• Use for: Depth of field, fog, atmospheric effects
• Essential for: Post-process DOF (faster than render DOF)
• Enable: Data → Z

Mist:

• Contains: Depth-based gradient (customizable range)
• Appears as: Grayscale gradient based on distance
• Use for: Atmospheric haze, distance fog
• Configure in: World settings (Mist Pass section)
• Enable: Data → Mist

Normal:

• Contains: Surface normal directions
• Appears as: Colorful (RGB = XYZ directions)
• Use for: Relighting, edge detection, technical masks
• Advanced technique: Can fake lighting changes in post
• Enable: Data → Normal

Object Index / Material Index:

• Contains: Unique ID for each object/material
• Use for: Selecting specific objects in comp for adjustment
• Example: Brighten just the car without affecting background
• Setup required: Assign pass index numbers in object/material properties
• Enable: Data → Object Index / Material Index

💡 Light Passes (Lighting Components)

These separate different types of lighting:

Diffuse Direct / Indirect:

• Direct: Light hitting surfaces directly from lights
• Indirect: Light bouncing around (global illumination)
• Appears as: Colored images (the lit diffuse surfaces)
• Use for: Adjusting GI strength, controlling direct/indirect balance
• Enable: Light → Diffuse → Direct and/or Indirect

Glossy Direct / Indirect:

• Direct: Direct reflections (mirror-like, sharp)
• Indirect: Indirect reflections (environment reflections)
• Use for: Controlling reflection brightness and color
• Example: Make metal more/less reflective in post
• Enable: Light → Glossy → Direct and/or Indirect

Transmission Direct / Indirect:

• Contains: Light passing through transparent materials (glass)
• Direct: Light directly through transparent objects
• Indirect: Caustics and bounced transmitted light
• Use for: Adjusting glass/transparent object appearance
• Enable: Light → Transmission → Direct and/or Indirect

Emission:

• Contains: Light emitted from glowing materials
• Use for: Adjusting glow brightness, adding bloom/glare
• Perfect for: Controlling neon signs, screens, lights separately
• Enable: Light → Emission

Environment:

• Contains: Lighting from world environment (HDRI)
• Use for: Adjusting environment light strength/color
• Example: Make sky reflections more/less prominent
• Enable: Light → Environment

💡 Additional Useful Passes

Shadow:

• Contains: Shadow information
• Use for: Adjusting shadow strength/color separately
• Great for: Making shadows lighter/darker/warmer without re-render
• Enable: Light → Shadow

Ambient Occlusion (AO):

• Contains: Contact shadows in crevices and corners
• Appears as: Grayscale (white=exposed, black=occluded)
• Use for: Adding depth, enhancing details, darkening crevices
• Often added in post: Multiply over final image
• Enable: Data → Ambient Occlusion

Cryptomatte (Advanced):

• Contains: Automatic masks for every object and material
• Use for: Easy selection of any element in comp
• Professional feature: Industry-standard masking system
• Requires: Cryptomatte node in Compositor to use
• Enable: Data → Cryptomatte (Object, Material, Asset)

✅ Accessing and Using Passes

After enabling passes and rendering:

1. Render Layers Node Shows All Passes:
   • Each enabled pass appears as an output socket
   • Yellow sockets (color passes) and gray sockets (data passes)
   • Scroll down on Render Layers node to see all outputs
2. Connect Passes to Viewer:
   • Drag from any pass output to a Viewer node
   • See what each pass contains in backdrop
   • Explore your passes! Understand what each shows
3. Typical Workflow - Recombining Passes:
   • Start with individual light passes
   • Mix them together with Add nodes
   • Adjust individual pass colors/brightness before mixing
   • Gives you control over each lighting component

Example: Adjusting Reflections:

Render Layers → Glossy Indirect (reflections)
    → Color Correction (make 50% brighter)
        → Add with other passes
            → Final Result

Example: Adding More Shadows:

Render Layers → AO Pass
    → ColorRamp (adjust intensity)
        → Multiply over Combined pass
            → Darker crevices, more depth

🎯 Workshop: Enable and View Passes

Let's set up render passes and see what they contain!

1. Scene Preparation:
   • Use default scene or any scene with materials and lights
   • Make sure you're using Cycles render engine
   • Have at least one material with some specularity/reflection
2. Enable Essential Passes:
   • Open Properties → View Layer Properties (layers icon)
   • Scroll to "Passes" section
   • Enable these passes:
     • Data: Z, Mist (configure mist in World settings first)
     • Data: Normal
     • Data: Ambient Occlusion
     • Light: Emission (if you have emissive materials)
     • Light: Diffuse → Direct and Indirect
     • Light: Glossy → Indirect (for reflections)
3. Render the Scene:
   • F12 to render
   • Wait for completion
   • All enabled passes are now available!
4. View Passes in Compositor:
   • Switch to Compositing workspace
   • Enable "Use Nodes" and "Backdrop"
   • Look at Render Layers node—see all the output sockets!
5. Explore Each Pass:
   • Add Viewer node (Shift+A → Output → Viewer)
   • Connect different passes to Viewer one at a time
   • Look at Z: See depth information (grayscale)
   • Look at Normal: See colorful surface normals
   • Look at AO: See contact shadows
   • Look at Diffuse Direct: See direct lighting only
   • Look at Glossy Indirect: See reflections only
6. Compare Combined vs. Passes:
   • View "Combined" output (normal render)
   • View individual passes
   • Notice Combined = all passes added together

What You've Learned: Each pass isolates specific information. Z shows depth, AO shows occlusion, Diffuse shows base lighting, Glossy shows reflections. Understanding what each pass contains is crucial for using them effectively. Now you can adjust these components individually!

✅ Professional Pass Usage Patterns

1. Basic Pass Setup (Good for Most Projects):

• Enable: Combined (default), Z, AO
• Why: Combined for main image, Z for DOF, AO to enhance depth
• Workflow: Use Combined, add AO overlay, use Z for depth effects
• Fast and effective!

2. Full Control Setup (Maximum Flexibility):

• Enable: All light passes (Diffuse, Glossy, Transmission, etc.)
• Why: Control every lighting component separately
• Workflow: Rebuild image from passes, adjust each before combining
• Slower to set up, ultimate control

3. Character/Product Focus:

• Enable: Object Index, Cryptomatte, AO, Z
• Why: Easy selection and adjustment of specific objects
• Workflow: Use masks to adjust hero object without affecting environment
• Perfect for product visualization

4. Atmospheric Scene:

• Enable: Z, Mist, Emission, Environment
• Why: Control depth effects, fog, glows separately
• Workflow: Use Z/Mist for fog, Emission for glows, adjust atmosphere
• Great for exterior scenes, sci-fi environments

⚠️ Common Pass Pitfalls

1. Forgetting to Enable Passes Before Render

• Problem: Rendered without enabling passes, they're not available in comp
• Solution: Always check View Layer Properties → Passes before rendering
• Create a checklist for your typical pass setup

2. Not Understanding Pass Content

• Problem: Using passes incorrectly because you don't know what they contain
• Solution: Always view each pass first (connect to Viewer)
• Understand what you're working with before adjusting

3. Wrong Pass Combination

• Problem: Adding passes when you should multiply, or vice versa
• Solution: Light passes (Diffuse, Glossy) = Add together
• Masks (AO) = Multiply over image
• Learn the correct blend mode for each pass type

4. Enabling Too Many Passes

• Problem: Enabled every pass "just in case," huge memory usage
• Solution: Enable only what you'll actually use
• You can always render again with more passes if needed
• Start minimal, add as you discover needs

🎓 Render Passes Mastered!

You now understand the power of render passes! You know what they are, why they're essential, which passes exist, and how to enable and access them. This knowledge unlocks professional-level control over your renders. Next, we'll explore the essential Compositor nodes you'll use to manipulate these passes and create stunning results. Time to build some node trees!

💡 The Color Manipulation Toolkit

RGB Curves (The Master Control)

• Location: Shift+A → Color → RGB Curves
• What it does: Adjust brightness, contrast, color balance with curves
• Power: Most versatile color correction node
• Four curves: C (Combined/Luminosity), R (Red), G (Green), B (Blue)
• Usage:
  • Raise curve = brighten
  • Lower curve = darken
  • S-curve = increase contrast
  • Adjust individual RGB = color correction
• Pro tip: This is your "go-to" for most color work!

Hue/Saturation/Value

• Location: Shift+A → Color → Hue Saturation Value
• What it does: Adjust hue shift, saturation, and brightness
• Parameters:
  • Hue: Shift all colors (0.5 = opposite colors)
  • Saturation: Increase/decrease color intensity (0=grayscale, 2=hyper-saturated)
  • Value: Overall brightness adjustment
• Use case: Quick saturation boost, color shifts, desaturation effects

Bright/Contrast

• Location: Shift+A → Color → Bright/Contrast
• What it does: Simple brightness and contrast adjustment
• Simpler than RGB Curves but less flexible
• Parameters:
  • Bright: -100 to +100 (overall brightness)
  • Contrast: -100 to +100 (difference between darks and lights)
• Use case: Quick adjustments when you don't need curve precision

Color Balance

• Location: Shift+A → Color → Color Balance
• What it does: Adjust color tint in shadows, midtones, highlights separately
• Three sets of controls: Lift (shadows), Gamma (midtones), Gain (highlights)
• Each control: RGB sliders to add color tint
• Use case: Professional color grading, cinematic looks
• Example: Cool blue shadows, warm orange highlights (teal & orange look)

Gamma

• Location: Shift+A → Color → Gamma
• What it does: Adjust midtone brightness without crushing blacks/whites
• Value: 1.0 = no change, <1.0 = darken, >1.0 = brighten
• Use case: Subtle exposure adjustments that preserve detail

Exposure

• Location: Shift+A → Color → Exposure
• What it does: Simulates camera exposure adjustment (in stops)
• Exposure value: +1 = double brightness, -1 = half brightness
• Use case: Quick brightness fixes, HDR tone mapping
• Pro: Works like real camera exposure (photographers love this)

✅ Essential Effect Nodes

Blur

• Location: Shift+A → Filter → Blur
• What it does: Softens image with various blur algorithms
• Types:
  • Flat: Uniform blur (fastest)
  • Gaussian: Natural, smooth blur (most common)
  • Bokeh: Lens-style blur with configurable shape
• Variable Size: Can use Z pass to create depth-based blur (DOF!)
• Use cases: Depth of field, motion blur, softening, backgrounds

Glare

• Location: Shift+A → Filter → Glare
• What it does: Adds bloom/glow to bright areas
• Types:
  • Ghosts: Lens flare artifacts
  • Streaks: Star-like rays from bright spots
  • Fog Glow: Simple glow/bloom
  • Simple Star: Cross-shaped rays
• Threshold: Only affects pixels brighter than this value
• Use cases: Light glows, lens flares, magical effects, neon signs
• Pro tip: Use Fog Glow (threshold ~1.0) for subtle realistic bloom

Sharpen / Soften

• Location: Shift+A → Filter → Filter (then select type)
• Sharpen: Enhances edges, makes image crisper
• Soften: Subtle blur, smooths image
• Use case: Sharpen for extra clarity, soften for dreamy look
• Warning: Over-sharpening creates halos and artifacts!

Denoise

• Location: Shift+A → Filter → Denoise
• What it does: Removes render noise from Cycles renders
• Works with: Denoising Data pass (must enable in View Layer)
• Use case: Clean up grainy renders without increasing samples
• Huge time saver! Denoise in post instead of rendering 10x longer

Dilate/Erode

• Location: Shift+A → Filter → Dilate/Erode
• What it does: Expand (dilate) or shrink (erode) bright areas
• Use case: Modify masks, expand glows, adjust alpha edges
• Distance: Positive = dilate, negative = erode

💡 Layering and Blending Images

Mix (Alpha Over, Add, Multiply, etc.)

• Location: Shift+A → Color → Mix
• What it does: Combine two images using various blend modes
• Factor: 0 = Image 1 only, 1 = Image 2 only, 0.5 = 50/50 mix
• Essential Blend Modes:
  • Mix: Simple blend between two images
  • Add: Add pixel values (brightens, for light passes)
  • Multiply: Multiply values (darkens, for AO/shadows)
  • Screen: Opposite of multiply (brightens, for glows)
  • Overlay: Contrast-enhancing blend
• Use cases: Everything! Combining passes, adding effects, layering

Alpha Over

• Location: Shift+A → Color → Alpha Over
• What it does: Layer one image over another using alpha channel
• Respects transparency: Transparent areas show background
• Use case: Compositing elements, overlaying graphics, titles
• Premul option: Handle pre-multiplied alpha correctly

Z Combine

• Location: Shift+A → Color → Z Combine
• What it does: Combine two renders with depth information
• Uses Z pass: Correctly layers objects by distance
• Use case: Combining separately rendered elements with correct depth
• Example: Render character and environment separately, combine with correct depth

✅ Data Processing Nodes

ColorRamp

• Location: Shift+A → Converter → ColorRamp
• What it does: Remap values to colors/gradients
• Use cases:
  • Control mask strength (adjust gradient)
  • Threshold effects (tight stops = hard edges)
  • False color visualization (depth → rainbow colors)
  • Convert Z pass to usable mask range
• Same as Shader Editor ColorRamp but for images

RGB to BW (RGB to Black/White)

• Location: Shift+A → Converter → RGB to BW
• What it does: Convert color image to grayscale
• Uses luminance formula: Properly weighted conversion
• Use case: Create masks from color images, prepare for black/white output

Set Alpha

• Location: Shift+A → Converter → Set Alpha
• What it does: Replace alpha channel with custom mask
• Inputs: Image (color) + Alpha (grayscale mask)
• Use case: Apply custom masks to images, cutouts

Separate/Combine RGBA and HSVA

• Location: Shift+A → Converter → Separate/Combine
• Separate: Split image into R, G, B, A channels
• Combine: Merge channels back into image
• Use case: Process individual color channels, swap channels, effects

Math

• Location: Shift+A → Converter → Math
• What it does: Mathematical operations on value data
• Operations: Add, Subtract, Multiply, Divide, Power, and many more
• Use case: Adjust masks, normalize data, combine values

💡 Selection and Masking

ID Mask

• Location: Shift+A → Matte → ID Mask
• What it does: Create mask from Object Index or Material Index pass
• Setup: Assign pass index to objects/materials (in properties)
• Use case: Select specific objects for adjustment
• Example: Brighten only the car (index 1) without affecting road (index 2)

Cryptomatte

• Location: Shift+A → Matte → Cryptomatte
• What it does: Automatic masking system for any object/material
• Requires: Cryptomatte pass enabled in View Layer
• Pick objects: Click in viewport to select, creates mask automatically
• Professional tool: Industry standard for selection
• Massive time saver!

Double Edge Mask

• Location: Shift+A → Matte → Double Edge Mask
• What it does: Create mask from two edge masks (advanced)
• Use case: Rotoscoping, complex masking tasks
• Less common in basic compositing

✅ Transform and Distortion

Transform

• Location: Shift+A → Distort → Transform
• What it does: Move, rotate, scale image in 2D
• Parameters: X/Y position, rotation, scale
• Use case: Reposition elements, scale overlays, rotate images

Lens Distortion

• Location: Shift+A → Distort → Lens Distortion
• What it does: Add/remove barrel or pincushion distortion
• Dispersion: Chromatic aberration (color fringing)
• Use cases:
  • Add lens realism (slight distortion + dispersion)
  • Match CG to photographed background
  • Remove distortion from photos

Scale

• Location: Shift+A → Distort → Scale
• What it does: Resize image (simpler than Transform)
• Space: Relative (percentage) or Absolute (pixels)
• Use case: Quick image scaling

💡 Common Node Combinations

Basic Color Correction Stack:

Render Layers
    → RGB Curves (fix exposure/contrast)
        → Hue/Saturation/Value (adjust saturation)
            → Color Balance (add color grade)
                → Composite

Add Glow Effect:

Render Layers
    → Glare (Fog Glow, threshold 1.0)
        → Mix (Screen mode) with original
            → Composite

Depth of Field:

Render Layers Image → Blur (Variable Size, use Z pass)
Render Layers Z → Blur Z input
    → Composite

Add AO Pass:

Render Layers Combined → Mix (Multiply)
Render Layers AO → ColorRamp (adjust) → Mix Factor
    → Composite

Mask-Based Adjustment:

Render Layers → RGB Curves (brighten)
Render Layers → ID Mask (select object) → Mix Factor
Original Render → Mix Image 1
Adjusted Render → Mix Image 2
    → Composite (only selected object brightened!)

🎓 Essential Nodes Learned!

You now have a solid toolkit of Compositor nodes! You understand color correction nodes (RGB Curves, HSV, Color Balance), effect nodes (Blur, Glare, Denoise), mixing nodes (Mix, Alpha Over), converters (ColorRamp, Set Alpha), and masking nodes (ID Mask, Cryptomatte). These are your building blocks. Next, we'll put them to use in a complete color correction workflow—taking a render from good to great with professional color grading!

💡 Understanding Color Grading Goals

Technical Correction (Foundation):

• Fix exposure: Image not too dark or too bright
• White balance: Colors appear neutral (whites are white, not blue/yellow)
• Contrast: Good separation between darks and lights
• Color accuracy: Materials look right (skin tones, familiar objects)
• This is your baseline before creative grading

Creative Grading (Artistry):

• Mood setting: Warm colors = cozy/happy, cool colors = sterile/sad
• Stylization: Cinematic look, vintage film, high-key, low-key
• Visual hierarchy: Bright areas draw attention, darken distractions
• Consistency: Multiple shots match in color and tone
• This is where your artistic vision shines!

The Golden Rule:

Fix first, enhance second. Always correct technical issues (exposure, white balance) before applying creative looks. A stylistic grade on a technically flawed image looks amateur. A stylistic grade on a technically sound image looks professional.

✅ Step-by-Step Process

Step 1: Evaluate the Render

• Look at overall exposure (too dark/bright?)
• Check contrast (flat or too harsh?)
• Assess color balance (too warm/cool?)
• Identify problem areas (blown highlights, crushed blacks)
• Don't start adjusting yet—understand what needs fixing!

Step 2: Fix Exposure (Brightness)

• Node: RGB Curves or Exposure node
• Goal: Image has good overall brightness
• Check: Important details visible in both shadows and highlights
• RGB Curves approach: Adjust C (Combined) curve—raise for brighter, lower for darker
• Exposure approach: Adjust exposure value (works in stops like a camera)

Step 3: Set Contrast

• Node: RGB Curves (S-curve) or Bright/Contrast
• Goal: Good separation between darks and lights
• RGB Curves S-curve: Raise highlights (top-right), lower shadows (bottom-left)
• Creates: Punchy image with depth
• Warning: Too much = crushed blacks and blown whites!

Step 4: White Balance (Color Temperature)

• Node: RGB Curves or Color Balance
• Goal: Neutral colors look neutral (whites are white, not tinted)
• Too warm? Add blue (raise Blue curve or lower Red curve)
• Too cool? Add warmth (raise Red/lower Blue)
• Reference: Find something that should be neutral gray/white

Step 5: Saturation Adjustment

• Node: Hue/Saturation/Value
• Goal: Colors have appropriate intensity
• CG renders: Often too saturated—reduce slightly (0.9-0.95)
• Or boost: For vibrant, punchy looks (1.1-1.2)
• Desaturate completely (0.0): For black and white conversion

Step 6: Creative Color Grade (Optional)

• Node: Color Balance
• Goal: Apply stylistic color look
• Technique: Different colors in shadows vs. highlights
• Examples:
  • Teal shadows + orange highlights (cinematic)
  • Blue shadows + warm highlights (sunset feel)
  • Consistent cool tone (tech/sci-fi)

🎯 Workshop: Professional Color Grade

Let's grade a render from start to finish!

Setup:

1. Render any scene (default scene works, or use existing render)
2. Switch to Compositing workspace
3. Enable "Use Nodes" and "Backdrop"
4. You should see: Render Layers → Composite

Build the Grading Stack:

1. Add RGB Curves (Primary Color Correction):
   • Shift+A → Color → RGB Curves
   • Insert between Render Layers and Composite
   • Connect: Render Layers Image → RGB Curves Image
   • Connect: RGB Curves Image → Composite Image
2. Fix Exposure in RGB Curves:
   • Select C (Combined) curve
   • Click middle of curve, drag up to brighten (or down to darken)
   • Goal: Overall image properly exposed
   • Watch backdrop update in real-time
3. Add Contrast (S-Curve):
   • Still in RGB Curves, C curve
   • Click near top-right, drag slightly up (brighten highlights)
   • Click near bottom-left, drag slightly down (darken shadows)
   • Creates S-shape: More contrast!
   • Subtle is better: Don't overdo it
4. Adjust White Balance (if needed):
   • If image looks too warm (orange/yellow):
   • Select B (Blue) curve, drag up slightly in midtones
   • Or select R (Red) curve, drag down slightly
   • If image looks too cool (blue):
   • Do the opposite—reduce blue or add red
5. Add Hue/Saturation/Value Node:
   • Shift+A → Color → Hue Saturation Value
   • Insert after RGB Curves
   • Connect: RGB Curves → HSV → Composite
6. Adjust Saturation:
   • Reduce saturation slightly: 0.90-0.95
   • Or boost for vibrant look: 1.10-1.20
   • CG renders often benefit from slight desaturation
7. Add Color Balance (Creative Grade):
   • Shift+A → Color → Color Balance
   • Insert after HSV node
   • Connect: HSV → Color Balance → Composite
8. Apply Cinematic Look (Teal & Orange):
   • In Color Balance node:
   • Lift (Shadows): Add cyan/teal (move Blue slider right, Green slightly right)
   • Gamma (Midtones): Keep relatively neutral
   • Gain (Highlights): Add warmth (move Red slider right, Yellow/Green slightly right)
   • Result: Cool shadows, warm highlights—cinematic!
9. Compare Before/After:
   • Select any node in your stack
   • Press M to mute (bypass)
   • See original vs. graded
   • Press M again to unmute
   • Toggle to see your improvement!

Final Polish (Optional):

• Add subtle vignette (darken edges)
• Add film grain texture
• Slight sharpening
• These finishing touches add professional quality

💡 Popular Looks and How to Achieve Them

1. Cinematic (Teal & Orange)

• Shadows: Cool teal/cyan
• Highlights: Warm orange/yellow
• Why popular: Complementary colors, separates skin tones from backgrounds
• Seen in: Blockbuster movies, action films, thrillers
• Apply with: Color Balance (cool Lift, warm Gain)

2. High-Key (Bright & Airy)

• Overall: Very bright, minimal shadows
• Contrast: Low to medium
• Colors: Desaturated, pastel
• Mood: Light, optimistic, clean
• Apply with: RGB Curves (raise entire curve), reduce saturation

3. Low-Key (Dark & Moody)

• Overall: Dark, dramatic shadows
• Contrast: High
• Colors: Often desaturated or monochromatic
• Mood: Mysterious, dramatic, noir
• Apply with: RGB Curves (lower curve), strong S-curve for contrast

4. Vintage/Film Look

• Contrast: Reduced (lifted blacks)
• Colors: Muted, slightly warm
• Highlights: Slightly desaturated
• Add: Film grain, slight vignette
• Apply with: RGB Curves (flatten S, lift blacks), reduce saturation in highlights

5. HDR/Hyperreal

• Contrast: Enhanced but not crushed
• Colors: Highly saturated
• Clarity: High (sharp, detailed)
• Mood: Vibrant, attention-grabbing
• Apply with: Strong S-curve, boost saturation (1.3-1.5), sharpen