Sensor Size

Definition

The Sensor Size (English: Sensor Size or Image Format) is the physical size of a digital camera's image sensor, measured in inches or millimeters. It fundamentally determines the image format, the crop factor for lenses, the natural light sensitivity, and the optical characteristics of a camera.

In film production, the most common sensor formats are:

• Super35 (Super 35mm): The standard format for digital cinema
• Full Frame (36x24mm): Full format from photography
• M4/3 (Micro Four Thirds): Compact format with a 2x crop factor
• 2/3 inch: Traditional TV format
• RED Dragon/Monstro: 8K+ large format sensors

Historical Context

Film Era (Analog)

In the analog film era, 35mm film was the global standard for feature films and high-quality television. The actual exposed area was between the perforations (approx. 22mm x 12.3mm for Academy). Super35 expanded this area to utilize anamorphic formats.

Digital Revolution

With digitalization, various sensor standards emerged:

• 2007: RED One introduces 4K with a large sensor
• 2010: ARRI Alexa establishes Super35 as the cinema standard
• 2015: Sony Alpha 7 popularizes Full Frame for high-quality video
• 2018-2025: Hybrid approaches with Dual Native ISO and expanded formats

Technical Specifications

Super35 (DCI Standard)

Physical Dimension: 24.5mm × 13.8mm
Aspect Ratio: 16:9 or 17.5:1 (anamorphic)
Diagonal: ~28mm
Pixel Size (Alexa): ~5.3µm
Standard Cameras: ARRI Alexa Mini, Alexa 35
 RED Komodo, Phantom Flex
Lenses: EF, PL-Mount (35mm cinema lenses)

Full Frame (36x24mm)

Physical Dimension: 36mm × 24mm
Aspect Ratio: 3:2
Diagonal: ~43.3mm
Pixel Size: ~2-6µm (depending on camera)
Standard Cameras: Sony FX30, Canon EOS R5C
 Panasonic S1H, Blackmagic URSA Mini Pro
Lenses: RF, EF, L-Mount, E-Mount
Crop Factor to Super35: 1.5x (focal length effectively 50% longer)

M4/3 (Micro Four Thirds)

Physical Dimension: 17.3mm × 13mm
Aspect Ratio: 4:3 (originally)
Crop Factor to FF: 2.0x
Standard Cameras: Panasonic GH6, Olympus
Advantage: Compact, cost-effective
Disadvantage: Smaller sensors = higher noise

Differences and Consequences

1. Crop Factor and Focal Length Equivalence

A Crop Factor describes how much "stronger" a lens appears on a smaller sensor:

Practical Impact:

• On Full Frame with a 24mm lens: Very wide field of view (classic establishing shot)
• On Super35 with 24mm: Already a medium wide-angle
• On M4/3 with 24mm: Normal field of view like 48mm on Full Frame

2. Light Sensitivity and Pixel Size

The Pixel Size (in micrometers) determines the signal-to-noise ratio:

ARRI Alexa (Super35, 2880x1620px):
 Pixel Size = 5.32µm → Excellent SNR, low noise
 Base ISO = 160 (with standard ND)

Sony FX30 (APS-C, 6720x3780px):
 Pixel Size = ~2.4µm → More noise at high ISO
 Base ISO = 100 / Dual Native 100/3200

RED Monstro (8K, 8192x4320px):
 Pixel Size = 4.9µm → Very clean, ideal for grading
 Base ISO = 320

Rule of thumb: Larger pixels (on a large sensor) = better noise performance and greater light sensitivity.

3. Depth of Field and Optical Look

A larger sensor produces less depth of field at the same image composition:

Scene with 85mm lens, T/2.0, 3m focus distance:

Full Frame: ~3.2cm depth of field → Very shallow DOF
Super35: ~4.8cm depth of field → Still very shallow
M4/3: ~9.6cm depth of field → Significantly more in focus

This has dramatic consequences for image design:

• Full Frame: Requires T/4-T/5.6 for sufficient sharpness
• Super35: Classic film standard, T/2.0-T/2.8 very usable
• M4/3: Requires T/1.2 or ND filters for shallow DoF

4. Focal Length Equivalence in Practice

The term "Full Frame equivalent" is often used for comparison. This is problematic:

Scene: Portrait with classic "film look"

Film Standard (Super35):
 85mm lens at T/2.8 → 4cm DOF → Perfect focus

Full Frame Equivalent:
 One might think: 85mm / 1.5 = 56.7mm
 But: 56mm at F/1.8 has MORE shallow DOF than 85mm at T/2.8!
 Result: Too shallow depth of field, "digital look"

Correct Adjustment:
 Use 135mm at T/4.5 on Full Frame → Similar look

Practical Workflow

Pre-production

1. Make Format Decision

• Clarify budget and rental availability
• Analyze lighting conditions
• Define optical statement

1. Lens Planning

 Super35 Project:
 - Classic PL-Mount set (Master Primes)
 - Focal lengths: 27-180mm
 - T-stops: T/1.8-T/2.8 standard

 Full Frame Project:
 - RF or E-Mount set
 - Compensate for wider angle lenses
 - More T/1.2 or higher quality lenses needed

1. Lighting Planning

• Super35/Full Frame: Can work with less light
• M4/3 or RED: Requires more light for sufficient depth of field

Shooting

1. Know the Sensor Format:

// Example scene setup on ARRI Alexa 35 (Super35)
DoP: "I need 85mm for the close-up, T/2.8 for the performance"
1st AC: "Manageable with 6cm depth of field, but start at 3m distance"
A-Cam Op: "Movement will be critical, follow focus is necessary"

2. Lens Choice Influences Lighting Setup:

Full Frame (Sony FX30) with 35mm T/1.4:
 → Extreme shallow DoF, no room for movement
 → Solution: ND filter + T/4.5 or better lighting design

Super35 (ARRI Alexa Mini) with 35mm T/1.8:
 → Cinematic look, 5-7cm DOF
 → Operator has more leeway

3. Focus Strategy by Format:

Super35 (larger depth of field):
 - Zone focus possible
 - Operator movement allowed

Full Frame (shallow depth of field):
 - Critical follow focus
 - Remote head recommended
 - Lighting stands critical

Post-production

Sensor size influences:

1. Color Science

• Different sensors = different noise characteristics
• Debayer algorithm varies
• Adjust grading strategy

1. Noise Management

• Super35 with large pixels: Less noise reduction needed
• Full Frame smaller pixels: Aggressive denoising strategies
• RED 8K: Lots of noise, specialized tools (REDcine-X, DaVinci)

1. Zoom and Reframing

• Super35 4K: Limited zoom capability without visible quality loss
• RED 8K: Generously reframable in post

Comparison: Super35 vs. Full Frame

Super35 (Standard for High Cinema)

Advantages:

• ✓ Established standard (99% of feature films)
• ✓ Large pixel size = less noise
• ✓ Classic optics at T/2.0 work perfectly
• ✓ Predictable depth of field behavior
• ✓ Affordable (rental prices stable and low)

Disadvantages:

• ✗ Less wide-angle field of view
• ✗ Larger cameras
• ✗ 6K+ recording difficult

Cameras:

• ARRI Alexa 35, Alexa Mini LF
• RED Komodo, Red Dragon
• Blackmagic URSA Mini Pro (with EF lenses)

Full Frame (Hybrid Approach)

Advantages:

• ✓ Extreme wide-angle possible (24-28mm appear normal)
• ✓ Native photo lenses usable (cheaper)
• ✓ 8K+ possible
• ✓ More compact

Disadvantages:

• ✗ Very shallow depth of field = difficult to manage
• ✗ Less cinematic look (had to be compensated with T/0.95)
• ✗ Smaller pixel size = more noise at night
• ✗ Fewer rental options

Cameras:

• Sony FX30, FX7
• Canon EOS R5C, R6 Mark II
• Panasonic S1H
• Blackmagic URSA Mini Pro G2 (EF-Mount)

Special Formats

Anamorphic and Aspect Ratios

Super35 enables anamorphic lenses (4:3 sensor with 2x magnification):

DCI 2.39:1 (like all modern cinemas):
 Super35 Anamorphic: 24.5mm × 10.3mm → 2.4:1
 Super35 Spherical: Must be cropped (quality loss)

Full Frame Anamorphic:
 Rarer, 36mm × 15.1mm possible
 But: 3:1 aspect ratio instead of 2.39:1 is not ideal

Super35 with anamorphic lenses = gold standard for cinema aesthetics.

Large Format / RED Monstro

RED Monstro (8K, ~46.3mm × 24.6mm):
- Larger than Super35
- Larger than Full Frame
- Ideal for zoom reframing in post
- Base ISO 320
- Very high weight and storage requirements

Used for:

• High-budget features with 8K DCP
• Visual effects-heavy productions
• Premium grading with extreme zoom flexibility

Norms and Standards

DCI (Digital Cinema Initiatives)

• Super35 is the DCI standard
• 4K = 4096 x 2160 (17:9)
• All cinemas worldwide can play it
• Size standard: 24.5mm × 13.8mm effective area

UHD/4K Television

• 3840 x 2160 (16:9)
• Full Frame or Super35 compatible
• Streaming standard

8K

• 7680 x 4320
• Only RED or high-end Sony cameras
• Not yet widespread

Decision Criteria for a Production

See Also

• Full Frame – 36x24mm sensor standard
• Super35 – DCI cinema standard
• Base ISO – Native sensitivity by sensor size
• Dynamic Range – Relationship with sensor size
• Crop Factor – Focal length equivalence
• Optical Format – Digital vs. analog standards