【Unreal Engine】Adjusting Visual Effects with Post Process Volume: Exposure, Color Grading, Bloom

Finishing Touches with Post Process

Using Unreal Engine (UE) to set up wonderful 3D models and lighting, have you ever felt "somehow the visuals don't pop" or "can't achieve that professional work atmosphere"?

The cause often lies in the final visual "finishing touches." Just as photographers develop RAW images, UE scenes also need a process to adjust final color tone and atmosphere. The main character of this article, Post Process Volume, handles this "finishing" process.

This article thoroughly explains Post Process Volume basic usage to practical settings that dramatically improve visual quality, for UE beginners to intermediate developers.

---

What is Post Process Volume

Post Process Volume is a tool for applying overall visual effects (filters) to the final image captured by the camera.

Think of it as putting a filter over the entire game screen. If lighting and material settings are "ingredients," Post Process Volume is "seasoning" and "plating."

Terminology: Post Process

Post Process refers to processing done at "the final stage of rendering (after everything has been drawn)." Specifically, it refers to effects like overall screen color correction, exposure adjustment, depth of field, bloom (light bleed), etc.

---

Basic Usage

Using Post Process Volume is very simple.

Step 1: Placement in Scene

1. Select the "Volumes" category from the UE editor's "Place Actors" panel.
2. Drag and drop "Post Process Volume" into the scene.

Step 2: Effect Range Setting (Most Important!)

Just placing it only applies effects when the camera is inside the volume's boundaries (default is a cube). To apply effects to the entire scene, the following setting is necessary:

1. Select "Post Process Volume" in the Details panel.
2. Type "unbound" in the search box and turn on the "Infinite Extent (Unbound)" checkbox.

💡 Best Practice: Always enable this setting when you want effects applied to the entire scene. Only uncheck this and adjust volume size when you want special effects applied only in specific areas (e.g., cave, underwater, etc.).

---

Main Settings

Post Process Volume has numerous settings, but here are the especially important ones that determine "professional-looking" visuals.

Category	Setting	Effect Overview	Adjustment Point
Lens	Bloom	Bleeds light from bright areas, creating a dreamy atmosphere.	Too strong makes the entire screen whitish, so keep Intensity moderate.
Exposure	Metering Mode	How camera exposure (brightness) is measured.	Usually default is OK. Set to Manual if you want to fix manually.
Exposure	Min/Max Brightness	Auto Exposure minimum/maximum brightness.	Narrowing this range prevents sudden brightness changes, stabilizing visuals.
Color Grading	Global	Overall screen color correction. Adjust Saturation, Contrast, etc.	Just slightly increasing Contrast adds visual punch.
Rendering Features	Ambient Occlusion (AO)	Adds shadows to gaps and corners of objects, emphasizing dimensionality.	Too high Intensity makes things unnaturally dark.
Lens	Vignette	Darkens screen edges, drawing focus to the center.	Applying just slightly creates a cinematic atmosphere.

Practical Example: Creating "Atmosphere" with Color Grading

Color Grading settings primarily determine visual atmosphere.

For example, to create a "warm, nostalgic atmosphere":

1. Adjust Color Grading > Global > White Balance > Temp toward positive values to make everything warm and yellowish.
2. Slightly increase Color Grading > Global > Contrast (e.g., 1.0 → 1.1) to add punch.
3. Slightly decrease Color Grading > Global > Saturation (e.g., 1.0 → 0.9) to reduce saturation, creating an old photograph feel.

💡 About UE's Temp Value

The Temp parameter in UE's Color Grading conceptually functions as "color temperature" adjustment. Specific values and units in the engine UI may vary by version or settings, so adjusting values while visually confirming in the actual editor is recommended. Positive direction gives warm colors (yellow-orange), negative direction gives cool colors (blue)—this is consistent.

---

Common Mistakes and Best Practices

❌ Common Mistakes

Mistake	Description	Solution
Overlooking Infinite Extent (Unbound)	Wanting effects on the entire scene but forgetting to check Unbound.	Turn on Infinite Extent (Unbound) in Details panel.
Extreme Value Adjustments	Cranking bloom or contrast to near maximum, breaking the visuals.	Always adjust conservatively, little by little, staying within the range where effects look natural.
Leaving Auto Exposure Alone	Auto Exposure range is too wide, causing brightness to change drastically when moving the camera.	Set Min Brightness and Max Brightness difference small to make exposure changes gradual.

✅ Best Practices

1. Enable Only Necessary Effects: Each Post Process Volume setting is disabled by default (unchecked state). Every enabled effect adds rendering load, so enabling only truly necessary effects is basic performance optimization.
2. Use Multiple Volumes Strategically: Use a "base volume" (Unbound) applied to the entire scene, and "local volumes" (not Unbound) applied only in specific places (e.g., dark room, underwater, SF-style space). Set "Priority" on local volumes higher than the base volume to smoothly switch effects the moment you enter the area.

---

Summary

Post Process Volume is a powerful tool for taking your Unreal Engine visual expression to the next level.

Key Point	Description
Role	"Finishing" role of filtering the final image captured by camera.
Basics	Turn on Infinite Extent (Unbound) to apply to entire scene.
Important Settings	Adjust Exposure, Color Grading, and Bloom.
Optimization	Enable only necessary effects and adjust settings conservatively.

💡 UE5's Lumen and Post Process Volume

UE5 introduces Lumen (global illumination and reflection system). Post Process Volume has Lumen-related settings (Global Illumination section) to adjust Lumen quality and reflection precision. However, it's important to be aware of the role division: basic visual "appearance" with Post Process Volume, light physics simulation with Lumen/lighting settings. Don't try to solve everything with Post Process Volume alone—do basic lighting design first.

Use this knowledge to dramatically improve your Unreal Engine project's visual quality.