Part 17: CAMERA MATCHING

UE5 provides multiple camera systems for different needs:

Think in three layers:

1) FOV Calculation

2) Physical Simulation

3) Render Target

Use when:

• Gameplay cameras (first-person, third-person)
• You want to specify FOV directly
• Physical accuracy isn't required
• Simple cutscenes without camera matching

Don't use when:

• You need accurate depth of field matching a real camera
• Matching real-world camera specifications
• Working with cinematographers who think in focal lengths

In a Blueprint:

1. Add Component → Camera
2. Set Field of View (e.g., 90)
3. Configure Post Process Settings if needed

As a standalone Actor:

1. Place Actors → Camera Actor
2. This is just a Camera Component wrapped in an Actor

First, enable physical camera simulation:

Cine Camera Actor → Details → Current Camera Settings:
    ☑ Constrain Aspect Ratio: True (optional, locks aspect)

Cine Camera Actor → Details → Camera Options:
    ☑ Physically Based Camera: True  ← CRITICAL for accurate simulation

With Physically Based Camera enabled, the camera uses real-world units and physically accurate calculations for DOF and exposure.

The Lens Settings section controls zoom range and current focal length:

For camera matching, set Current Focal Length to your camera's actual focal length in mm.

Note: Min/Max are constraints for runtime zoom. For static camera matching, only Current Focal Length matters.

Unlike Camera Component, Cine Camera calculates FOV from sensor and lens:

FOV = 2 × arctan(SensorWidth / (2 × FocalLength))

Calculate FOV from sensor + focal length:

Example: Full Frame (36mm wide) @ 50mm lens
FOV = 2 × arctan(36 / 100)
FOV = 2 × arctan(0.36)
FOV = 2 × 19.8°
FOV = 39.6° horizontal

Calculate Sensor Size from FOV + Focal Length:

SensorWidth = 2 × FocalLength × tan(FOV / 2)

Example: 28.684° FOV @ 25mm focal length
SensorWidth = 2 × 25 × tan(14.342°)
SensorWidth = 50 × 0.2556
SensorWidth = 12.78 mm

Calculate Sensor Size from Pixel Pitch + Resolution:

SensorWidth = PixelPitch (µm) × PixelCount / 1000

Example: 2.4 µm pitch × 5472 pixels wide
SensorWidth = 2.4 × 5472 / 1000 = 13.13 mm

Calculate Sensor Height from Width + Aspect Ratio:

AspectRatio = ImageBufferWidth / ImageBufferHeight
SensorHeight = SensorWidth / AspectRatio

Example: 6650 × 3790 resolution, 12.78mm sensor width
AspectRatio = 6650 / 3790 = 1.754
SensorHeight = 12.78 / 1.754 = 7.29 mm

Summary — What You Need:

Tip: Pixel pitch gives the most accurate sensor size. Check camera specs or datasheets for this value.

UE5 has sensor width in THREE locations. Know which one you're setting.

Cine Camera → Current Camera Settings → Filmback:
  Sensor Width: 36.0 mm   ← Sets FOV + DOF for Cine Camera

Post Process → Lens → Depth of Field:
  Sensor Width: 24.576 mm  ← Sets DOF blur for regular cameras

For Cine Camera: Use Filmback settings. The Post Process Sensor Width is ignored.

For Camera Component: Use Post Process → Lens → Depth of Field → Sensor Width to control DOF blur amount.

Cine Camera has TWO aperture settings. They do different things.

Lens Settings:
  Current Aperture: 2.8  ← Controls DOF blur

Post Process → Camera:
  Aperture: 2.8  ← Used in exposure formula

For camera matching: Set BOTH to the same f-stop value.

The critical distinction: Only the Post Process aperture affects brightness. The Lens Settings aperture only affects blur.

*Shutter Speed affects exposure calculation but motion blur is controlled separately via Post Process Volume → Motion Blur settings (Amount, Max).

Cine Camera includes common sensor presets:

Or enter custom values to match any camera.

• Security camera monitors
• Mirrors and portals
• Minimaps
• Picture-in-picture
• Off-screen rendering for effects

Scene Capture does NOT inherit from Post Process Volumes or other cameras. You must configure it manually.

If your Scene Capture should match your main camera's exposure, you must copy all the Post Process settings yourself.

Each Scene Capture renders the scene again — like having another camera. Consider:

• Lower resolution render targets
• Capturing less frequently (not every frame)
• Limiting active Scene Captures

• Matching footage for VFX compositing
• Recreating a specific camera's "look"
• Accurate product visualization
• Training ML models with consistent data

What controls exposure (image brightness)?

These three form the exposure triangle. In UE5 with Manual metering, all three must be set correctly to match your reference camera's exposure.

To verify your settings match, calculate the Exposure Value (EV100):

EV100 = log₂(N² / t) - log₂(ISO / 100)

Where:
  N = f-stop number (aperture)
  t = shutter speed in seconds (e.g., 1/125 = 0.008)

Quick calculation:

Example: f/2.8, 1/125s, ISO 200

Step 1: N² / t = 2.8² / 0.008 = 7.84 / 0.008 = 980
Step 2: log₂(980) ≈ 9.94
Step 3: log₂(200/100) = log₂(2) = 1
Step 4: EV100 = 9.94 - 1 = 8.94 ≈ EV 9

Common EV100 reference values:

Tip: If your calculated EV doesn't match the scene type, double-check your camera settings or adjust Exposure Compensation.

The filmback is the sensor/film size. This determines FOV characteristics and DOF behavior.

Cine Camera Actor → Current Camera Settings → Filmback

Common sizes:
  Full Frame:    36 × 24 mm
  Super 35:      24.89 × 18.66 mm
  APS-C:         23.6 × 15.6 mm
  Micro 4/3:     17.3 × 13 mm

For phones: Look up the actual sensor size, not the "equivalent" focal length.

Before ISO and Shutter Speed affect anything:

Project Settings → Rendering → Default Settings:
  [x] Apply Physical Camera Exposure  ← MUST be enabled

Post Process (PPV or Camera) → Exposure:
  Metering Mode: Manual  ← Required for physical values

UE5 takes only the denominator:

Higher value = faster shutter = darker image

For accurate depth of field, use ACTUAL sensor size and ACTUAL focal length — NOT full-frame equivalents.

"Full-frame equivalent" describes FOV, not DOF. Two cameras with the same FOV can have completely different depth of field:

Full Frame @ 50mm f/2.0:
  → Large sensor + long focal length
  → Shallow DOF, creamy background blur

Phone @ 6.9mm f/1.68 (same FOV):
  → Tiny sensor + short focal length
  → Deep DOF, almost everything in focus

DOF is proportional to:

(FocalLength²) / SensorSize

A 50mm lens on full frame produces FAR more blur than a 6.9mm lens on a phone sensor, even at similar apertures.

Wrong approach:

"Phone says 24mm equivalent, so I'll use 24mm focal length"
→ DOF will be completely wrong

Correct approach:

Filmback: 9.8 × 7.4 mm (actual phone sensor)
Focal Length: 6.9 mm (actual phone lens)
→ DOF will match the phone's deep focus look

Phone sensors are tiny. Even at f/1.7, the short focal length produces deep DOF. The phone uses computational photography to simulate shallow DOF — because the optics physically cannot produce it.

• 47×46mm filmback matches Polaroid's instant film frame
• 51.1mm focal length gives the correct FOV (~48°)
• f/9 aperture matches the camera's daylight setting
• ISO 640 matches i-Type film sensitivity
• Deep focus (3km) simulates the fixed-focus lens

Why 125 for the Pixel example?

Phone cameras use auto exposure, adjusting ISO and shutter speed constantly. The value 125 represents a typical daylight scenario:

Real shutter speed: 1/125 second
UE5 expects denominator only: 125

Calculating from real camera data:

If your phone's camera app shows "1/125s" or you extract EXIF data showing 0.008s exposure:

0.008 seconds = 1/125 second
UE5 value = 125

Common phone shutter speeds:

Tip: Check your photo's EXIF data (Google Photos → Info) to get the exact shutter speed used for a specific shot you want to match.

Place BP_LHT_Calibration (from Part 16) in your scene:

1. If 18% grey looks correct → exposure is right
2. If 90% white is clipped → reduce exposure
3. If 5% black has no detail → increase exposure
4. If chrome shows clean reflections → lighting environment is good

Key Points:

• Camera Component — basic viewpoint, specify FOV directly
• Cine Camera Actor — physical simulation, FOV calculated from sensor + lens
• Scene Capture 2D — renders to texture, must configure manually
• Dual aperture problem — Lens Settings aperture = DOF, Post Process aperture = exposure
• Apply Physical Camera Exposure must be enabled for ISO/Shutter to work
• Camera matching requires actual values, not full-frame equivalents
• DOF depends on actual sensor size — equivalents only describe FOV
• Phone cameras have deep DOF due to tiny sensors and short focal lengths

You've now completed the camera and exposure pipeline — from physical camera concepts through UE5's systems and practical matching workflows. In Part 18: Wrap-Up, we'll summarize the key takeaways from the entire course.