Bokeh

Bokeh (Out-of-Focus Quality)

Bokeh (Japanese: ボケ, literally "blur" or "haze") refers to the aesthetic quality and visual rendering of out-of-focus areas – not the amount of blur itself (that is depth of field), but how that blur looks, feels, and behaves.

Definition and Distinction

Depth of Field vs. Bokeh:

• Depth of Field: Quantitative question – how much of the image is in focus? (measured in cm or m)
• Bokeh: Qualitative question – what does the blur look like? (descriptive: soft, creamy, harsh, etc.)

A lens can:

• Large depth of field + good bokeh = modern cinema lenses
• Shallow depth of field + bad bokeh = old photo equipment
• Large depth of field + bad bokeh = smartphone camera

Physical Principles

The Circle of Confusion

Bokeh arises from the optical projection of point light sources outside the depth of field:

Plane of Focus:
|
└─ Subject
 ↓ (Light rays through lens)
 ┌────────┐
 │ Aperture │ ← Determines size and shape
 └────────┘
 ↓
 Bokeh disc on sensor

The aperture acts as an opening (shape) and projects its form onto the sensor:

• Round aperture (9+ blades) → circular bokeh
• Pentagonal aperture → pentagonal bokeh
• Elliptical aperture (Anamorphic) → oval/elliptical bokeh

Mathematics:

Bokeh Diameter = (Lens Aperture ÷ Focal Length) × Defocus Distance

Example (85mm T/1.8):
- Aperture: 47mm
- Focal Length: 85mm
- Subject 1m in front of focal plane
- Bokeh Diameter ≈ (47÷85) × 1000 ≈ 550 pixels

Larger diameter = bigger, more visible bokeh circles

Bokeh Characteristics

"Good" (Creamy) Bokeh

Characteristics:

• Soft, round transitions at the edges of bokeh discs
• Gradual transition from sharp focus to the out-of-focus area
• No onion ring patterns (concentric brightness rings)
• Visually pleasing, not distracting
• Enables visual hierarchy through focus stacking

Optical Causes:

• High-quality lens coatings (modern multi-layer coatings)
• Spherical aberration optimized for smooth transitions
• 9+ rounded aperture blades
• High-quality glass elements

Premium Lenses with Creamy Bokeh:

• ARRI Signature Primes (T/1.8): Specifically optimized for creamy bokeh
• Cooke S4/i: Legendary for soft, cinematic bokeh
• Zeiss Master Prime: Classically sharp optics with elegant blur
• Zeiss Supreme Prime: State-of-the-art bokeh with digital optimization

"Bad" (Busy) Bokeh

Characteristics:

• Harsh edges on bokeh discs
• Onion ring patterns (double contours due to aberrational optics)
• Busy bokeh (too many small discs, appears "nervous")
• Can look distracting and cheap
• Dependent on focus point and background

Common Causes:

• Internal reflections (poor coatings)
• Spherical aberration not optimized
• Too few or angular aperture blades (under 7)
• Inexpensive optics with poor manufacturing tolerances

Examples (often used deliberately):

• Sony FE-Mount Kit Lenses: f/3.5–5.6 (broadcast quality)
• Cheap DSLR Zoom: 18–55mm kit (textbook example of bad bokeh)
• Old Agfa/Jena Lenses: Charming "nervous" vintage bokeh

Factors Influencing Bokeh Quality

1. Aperture Blade Geometry

Professional Cinema Lenses: All Cooke, ARRI, and Zeiss cine lenses use 9+ blades.

2. Aperture Setting (f-Stop)

Aperture wide open (f/1.4):
└─ Aperture shape clearly visible as bokeh shape

Aperture mid-range (f/2.8):
└─ Bokeh shape still visible, slightly more angular

Aperture stopped down (f/5.6):
└─ Bokeh becomes very polygonal (the blades become visible)

Aperture very stopped down (f/11):
└─ Diffraction spikes instead of bokeh discs

Consequence: For cinematic bokeh, shoot at f/1.4–f/2.8.

3. Spherical Aberration (SA)

Spherical aberration affects how sharp the edges of bokeh discs are:

• Positive SA: Bokeh edges are soft and blurred (creamy)
• Negative SA: Bokeh edges are sharp and defined (busy)
• Optimized: Balance between creaminess and control

Modern Approach: Zeiss and ARRI have calibrated their primes for slight positive SA to achieve creamy bokeh.

4. Focal Length

Longer focal lengths automatically produce "better" bokeh because the circle of confusion is larger:

At the same aperture (f/2.0), same depth of field, but different focal lengths:

35mm: Smaller bokeh discs → details visible → more complex bokeh
50mm: Medium bokeh discs
85mm: Larger bokeh discs → detail blurs → creamier bokeh
135mm: Very large discs → maximum creamy bokeh

Implication: For portrait shots, DPs use 85–135mm to naturally achieve better bokeh.

5. Focus Distance

Closer focusing = greater blur = larger bokeh discs = more visible bokeh.

Focus at 1m: Large bokeh
Focus at 3m: Medium bokeh
Focus at ∞: No bokeh (everything is infinite)

6. Background Composition

The actual background significantly influences the perception of bokeh:

• Bright bokeh (lights, white walls, sky): Visible and critical
• Dark bokeh (trees, shadow areas): Less visible
• Textured bokeh (many small details): Appears "busy"
• Simple bokeh (uniform): Appears "creamy"

Practical Advice: DPs position actors against dark, simple backgrounds for optimal bokeh rendering.

Bokeh Variants in Cinematography

Spherical Bokeh (Standard)

Most modern cinema lenses produce spherical bokeh with round bokeh discs. This is the standard for drama and feature films.

Lenses: ARRI Signature Primes, Zeiss Master Prime, Cooke S4/i

Anamorphic Bokeh (Wide-Elliptical)

Anamorphic lenses compress the image vertically, creating elliptical, wide-stretched bokeh discs – the characteristic "cinematic" look.

Spherical Bokeh: Anamorphic Bokeh:
 ●●●● ⬭⬭⬭⬭
 ●●●● ⬭⬭⬭⬭
 ●●●● ⬭⬭⬭⬭

Lenses: Cooke Anamorphic 40mm–100mm, ARRI Master Anamorphic, Panavision G-Series

Cat's-Eye Bokeh (Edge Distortion)

At the edges of the frame, bokeh discs can appear oval or lens-shaped distorted – also called "mechanical vignetting." This is a natural aberration and is often perceived as charming.

Common in: Vintage anamorphic lenses, at extreme angles

Swirly Bokeh (Vortex Effect)

Certain vintage lenses (especially Soviet optics like the Helios 44-2) produce a characteristic swirling bokeh pattern. This is a positive spherical aberration combined with astigmatism.

Lenses: Helios 44-2, old Zeiss Flektogon, Pentax Takumar SMC

Application: Retro aesthetic, indie film, used intentionally for character

Neutral Bokeh (Modern Flatness)

The latest technology (especially Zeiss Supreme Prime, ARRI Signature Prime) intentionally produces neutral, non-characteristic bokeh that subordinates itself to the background without having a visual signature.

Advantage: Focus remains on the story, not on optical charm

Bokeh in Practice: Design and Control

Bokeh-Conscious Production

Pre-production Planning:

1. Identify scenarios where bokeh will be visible
2. Test lenses with actual backgrounds (location scouting)
3. Adjust lighting and background design for optimal bokeh rendering

Example:

Scenario: Intimate conversation between two characters, evening light

DP decides:
- 85mm Zeiss Master Prime T/2.0 (creamy bokeh)
- Focal length chosen for large bokeh discs
- Background: Soft, dark plants (no harsh light on background)
- Lighting: Small, warm lights as bokeh accents

Result: Maximum creamy bokeh, enhancing intimacy

On-Set Bokeh Control

1. Position Background: Closer to the lens = greater defocus = better bokeh
2. Place Lights: Small, bright lights as bokeh accents (streetlights, neon, house lights)
3. Focus Distance: Closer to the subject = more bokeh (but focus pulling becomes harder)
4. Stabilize Aperture: Constant aperture during camera movements = consistent bokeh

Premium Lenses and Their Bokeh Characteristics

ARRI Signature Primes

• Bokeh: Ultra-creamy and soft
• Characteristic: Modern, neutral, focused on optical perfection
• Best for: High-end drama where optics should remain invisible
• T-Stop: T/1.8 throughout

Cooke S4/i

• Bokeh: Legendarily creamy and warm
• Characteristic: Slight positive spherical aberration, soft highlights
• Best for: Portraits, drama, romantic scenes
• T-Stop: T/2.0
• Historical Background: Industry standard since the 1980s

Zeiss Master Prime

• Bokeh: Classically elegant, precise edges
• Characteristic: Ultra-sharp with a subtle but visible optical signature
• Best for: Drama with a craft aesthetic
• T-Stop: T/2.0

Zeiss Supreme Prime

• Bokeh: Modern, digitally optimized, very neutral
• Characteristic: Designed for digital cameras, minimal aberration
• Best for: Modern, digital-native productions
• T-Stop: T/1.5 (extremely fast)

Panavision G-Series Anamorphic

• Bokeh: Wide, horizontal elliptical discs
• Characteristic: The iconic "anamorphic bokeh," 2.39:1 native
• Best for: Blockbuster aesthetic
• T-Stop: T/2.0–T/2.3

Cooke Anamorphic Optics

• Bokeh: Oval, horizontal, creamy, and warm
• Characteristic: Softness and warmth combined with anamorphic characteristics
• Best for: High-quality drama and prestige productions
• T-Stop: T/2.3

Bokeh-Specific Films and References

Frequently Asked Questions

Q: Can bad bokeh be corrected in post-production?
A: Practically impossible. Bokeh is an optical characteristic of the original footage. Color grading can make the background brighter/darker, but it cannot change the shape of the bokeh discs. Therefore, camera selection in pre-production is crucial.

Q: Why do lenses with better bokeh cost so much more?
A: Creamy bokeh requires precise optical calculation and high-quality glass coatings. Modern CNC manufacturing can produce this more affordably today, but premium manufacturers (ARRI, Cooke, Zeiss) have decades of design secrets.

Q: Is anamorphic bokeh objectively "better" than spherical bokeh?
A: No, it's simply different. Anamorphic bokeh is more characteristic and recognizable; spherical bokeh can be creamier and more invisible. The choice depends on the visual strategy.

Q: Can I achieve good bokeh with inexpensive lenses?
A: With optimal composition (long focal length, wide aperture, dark background), yes. But the optical quality will never be as creamy as premium primes.

Related Terms: Depth of Field, Aperture, Circle of Confusion, Spherical Aberration, Anamorphic Lenses, Focus Pulling