Depth of Field Field Guide - Practical Reference for Film Photography

Purpose: Quick reference for calculating and estimating depth of field in the field Film Formats: 35mm (24×36mm) and 120 Medium Format (6×6, 6×7, 6×9) Updated: 2026-05-23

What is Depth of Field?

Depth of Field (DoF): The zone of acceptable sharpness in front of and behind the focused subject.

Three Controlling Factors

Aperture (f-stop) - Smaller aperture (higher f-number) = Greater DoF
Focal Length - Shorter lens = Greater DoF
Focus Distance - Greater distance = Greater DoF

The Physics

graph TD
A[Subject in Focus] --> B[Zone of Acceptable Sharpness]
B --> C[Near Limit of DoF]
B --> D[Far Limit of DoF]
C --> E[Everything Closer: Progressively Blurred]
D --> F[Everything Farther: Progressively Blurred]

DoF Distribution Rule

Approximate ratio (subject at moderate distance): - 1/3 of DoF falls in front of the focus point - 2/3 of DoF falls behind the focus point

Exception: At very close focus distances (macro range), the distribution approaches 1:1 (equal in front and behind).

The Mathematics

Circle of Confusion (CoC)

Definition: The maximum blur spot diameter that still appears sharp to the human eye at standard viewing distance.

Standard CoC values:

Format	Frame Size	Standard CoC
35mm Full Frame	24 × 36 mm	0.030 mm
120 - 6×6	56 × 56 mm	0.050 mm
120 - 6×7	56 × 70 mm	0.053 mm
120 - 6×9	56 × 84 mm	0.060 mm

Derivation: CoC ≈ diagonal / 1500 Example (35mm): √(24² + 36²) / 1500 = 43.3 / 1500 ≈ 0.029 mm

Simplified DoF Formula (Field Use)

For quick mental calculation:

Near Limit ≈ D / (1 + D·A·C / f²)
Far Limit ≈ D / (1 - D·A·C / f²)

Where:
D = Focus distance (meters)
A = Aperture (f-number, e.g., 8 for f/8)
C = Circle of Confusion (mm)
f = Focal length (mm)

Total Depth of Field

Total DoF = Far Limit - Near Limit

Hyperfocal Distance

Definition: The focus distance where DoF extends from half that distance to infinity.

H = f² / (A × C) + f

Where:
H = Hyperfocal distance (mm, convert to meters)
f = Focal length (mm)
A = f-number
C = Circle of Confusion (mm)

Simplified (for field use, f is small compared to H):

H ≈ f² / (A × C)

Practical use: Focus at hyperfocal distance for maximum DoF in landscape photography.

35mm Format (24×36mm) Quick Reference

Standard CoC: 0.030 mm

Hyperfocal Distance Tables

50mm Lens (Normal)

f-stop	Hyperfocal Distance	DoF at 3m	DoF at 10m
f/2.8	29.8 m	2.73 - 3.32 m (0.59 m)	6.43 - 20.0 m (13.6 m)
f/4	20.8 m	2.60 - 3.50 m (0.90 m)	5.56 - ∞
f/5.6	14.9 m	2.45 - 3.75 m (1.30 m)	4.76 - ∞
f/8	10.4 m	2.27 - 4.17 m (1.90 m)	4.00 - ∞
f/11	7.6 m	2.11 - 4.76 m (2.65 m)	3.45 - ∞
f/16	5.2 m	1.88 - 6.25 m (4.37 m)	2.86 - ∞

35mm Lens (Wide)

f-stop	Hyperfocal Distance	DoF at 2m	DoF at 5m
f/2.8	14.6 m	1.59 - 2.67 m (1.08 m)	2.78 - ∞
f/4	10.2 m	1.49 - 3.03 m (1.54 m)	2.50 - ∞
f/5.6	7.3 m	1.39 - 3.70 m (2.31 m)	2.27 - ∞
f/8	5.1 m	1.27 - 5.88 m (4.61 m)	2.04 - ∞
f/11	3.7 m	1.16 - ∞	1.85 - ∞
f/16	2.6 m	1.04 - ∞	1.64 - ∞

85mm Lens (Portrait)

f-stop	Hyperfocal Distance	DoF at 3m	DoF at 10m
f/2	120.4 m	2.93 - 3.07 m (0.14 m)	9.20 - 11.1 m (1.9 m)
f/2.8	86.0 m	2.90 - 3.10 m (0.20 m)	8.93 - 11.6 m (2.7 m)
f/4	60.2 m	2.86 - 3.15 m (0.29 m)	8.57 - 12.4 m (3.8 m)
f/5.6	43.0 m	2.81 - 3.22 m (0.41 m)	8.16 - 13.6 m (5.4 m)
f/8	30.1 m	2.75 - 3.30 m (0.55 m)	7.69 - 16.0 m (8.3 m)
f/11	21.8 m	2.68 - 3.41 m (0.73 m)	7.23 - 20.0 m (12.8 m)

DoF Visualization (35mm, 50mm lens)

graph LR
subgraph "f/2.8 at 5m"
A1[3.85m] --- B1[5m SUBJECT] --- C1[7.14m]
end

subgraph "f/8 at 5m"
A2[3.33m] --- B2[5m SUBJECT] --- C2[10.0m]
end

subgraph "f/16 at 5m"
A3[2.63m] --- B3[5m SUBJECT] --- C3[∞]
end

120 Medium Format Quick Reference

Format Dimensions

Format	Frame Size	Aspect Ratio	CoC
6×6	56 × 56 mm	1:1 (square)	0.050 mm
6×7	56 × 70 mm	1:1.25	0.053 mm
6×9	56 × 84 mm	1:1.5	0.060 mm

Focal Length Equivalents to 35mm

Rule of Thumb: Medium format lenses are ~1.5-2× longer for equivalent field of view.

35mm Lens	6×6 Equivalent	6×7 Equivalent	6×9 Equivalent
28mm (wide)	50mm	55mm	65mm
35mm (wide)	60mm	65mm	75mm
50mm (normal)	80mm	90mm	105mm
85mm (portrait)	135mm	150mm	180mm
135mm (tele)	220mm	240mm	280mm

Hyperfocal Distance Tables - 6×6 Format

CoC: 0.050 mm

80mm Lens (Normal for 6×6)

f-stop	Hyperfocal Distance	DoF at 3m	DoF at 10m
f/2.8	25.6 m	2.78 - 3.26 m (0.48 m)	7.14 - 16.7 m (9.6 m)
f/4	17.9 m	2.67 - 3.41 m (0.74 m)	6.25 - 25.0 m (18.8 m)
f/5.6	12.8 m	2.54 - 3.61 m (1.07 m)	5.45 - ∞
f/8	8.9 m	2.38 - 3.95 m (1.57 m)	4.65 - ∞
f/11	6.5 m	2.22 - 4.44 m (2.22 m)	4.00 - ∞
f/16	4.5 m	1.96 - 5.88 m (3.92 m)	3.23 - ∞

150mm Lens (Portrait for 6×6)

f-stop	Hyperfocal Distance	DoF at 3m	DoF at 10m
f/2.8	90.0 m	2.93 - 3.08 m (0.15 m)	9.09 - 11.3 m (2.2 m)
f/4	63.0 m	2.90 - 3.11 m (0.21 m)	8.77 - 11.9 m (3.1 m)
f/5.6	45.0 m	2.87 - 3.15 m (0.28 m)	8.40 - 12.9 m (4.5 m)
f/8	31.5 m	2.83 - 3.20 m (0.37 m)	7.94 - 14.7 m (6.8 m)
f/11	22.9 m	2.78 - 3.26 m (0.48 m)	7.46 - 17.9 m (10.4 m)
f/16	15.8 m	2.71 - 3.36 m (0.65 m)	6.90 - 25.0 m (18.1 m)

6×7 vs 6×6 DoF Comparison

Same aperture and focus distance:

graph TD
A[Same: f/8, 5m focus, ~80mm lens] --> B[6×6: CoC 0.050mm]
A --> C[6×7: CoC 0.053mm]
B --> D["DoF: 3.57m - 9.09m (5.52m)"]
C --> E["DoF: 3.47m - 8.77m (5.30m)"]
E --> F[Slightly shallower DoF]

Practical takeaway: 6×7 and 6×9 have marginally shallower DoF than 6×6 at the same settings, but difference is small (< 5%).

Field Calculation Methods

Method 1: Mental Math (Hyperfocal Distance)

Step-by-step:

Know your hyperfocal distance for common f-stops (memorize or carry table)
Focus at hyperfocal distance - DoF extends from H/2 to infinity
Example: 35mm, 50mm lens, f/11
Hyperfocal = 7.6m
Focus at 7.6m → DoF from 3.8m to ∞

Method 2: Lens Distance Scales

Traditional lens markings:

∞ 30 10 5 3 2 1.5 1 0.7m
| | | | | | | | |
f/16 [=====================================]
f/11 [===================================]
f/8 [=================================]
f/5.6 [==============================]
f/4 [===========================]
f/2.8 [========================]

How to read: 1. Focus on subject (e.g., 5m) 2. Find aperture marks (e.g., f/11) 3. Read DoF limits where f/11 marks intersect distance scale 4. Result: ~3.5m to ~8m

Method 3: The "Rule of Thumb" (Portrait)

For portraits (shallow DoF desired):

Aperture: f/2 - f/4
Focal length: 85-135mm (35mm) or 150-250mm (120)
Distance: 2-4 meters
Expected DoF: 10-30cm (very shallow)

Quick check: At f/2.8, portrait lens, 3m distance → DoF ≈ face depth (nose to ears).

Method 4: Zone Focusing (Street Photography)

Pre-set for continuous action:

Choose aperture: f/8 or f/11 (deep DoF)
Choose focal length: 28-35mm (wide)
Focus at hyperfocal or slightly beyond
Effective DoF: 2m to infinity
Shoot without refocusing - everything in range is sharp

Example (35mm, 35mm lens, f/11): - Focus at 3.7m (hyperfocal) - DoF: 1.85m to ∞ - Never miss focus for subjects > 2m away

Practical Field Scenarios

Scenario 1: Landscape (Maximum DoF)

Goal: Sharp from foreground to infinity

Settings (35mm): - Lens: 24-35mm - Aperture: f/11 - f/16 - Focus: Hyperfocal distance

Calculation: 1. Find hyperfocal distance (e.g., 35mm @ f/11 = 3.7m) 2. Focus at 3.7m 3. DoF: 1.85m to ∞

120 format adjustment: - Use 50-65mm lens (equivalent FOV) - Same aperture (f/11-f/16) - Hyperfocal distance is longer, but DoF distribution similar

Scenario 2: Portrait (Shallow DoF)

Goal: Subject sharp, background blurred

Settings (35mm): - Lens: 85-135mm - Aperture: f/1.4 - f/2.8 - Focus: Precise on eyes

Calculation: 1. At 3m, 85mm, f/2.8 → DoF ≈ 20cm 2. Critical focus on nearest eye 3. Check far limit covers back of head

120 format (6×6): - Use 150-180mm lens - Same aperture - DoF will be similar (slightly shallower due to larger CoC)

Scenario 3: Street Photography

Goal: Ready for candid moments, no refocus needed

Settings (35mm): - Lens: 28-35mm - Aperture: f/8 - Focus: 5m (or hyperfocal)

Pre-calculated DoF: - 35mm @ f/8, focus 5m → DoF: 2.5m to ∞ - Keep subjects between 2.5m-10m for optimal sharpness

120 format (6×6): - Use 60-80mm lens - f/8-f/11 - Zone focus similarly effective

Scenario 4: Macro (Close-Up)

Goal: Sharp detail, manage extremely shallow DoF

Settings (35mm): - Lens: 50-105mm macro - Aperture: f/8 - f/16 (despite shallow DoF at close distance) - Focus: 1:1 magnification (life-size)

At 1:1 magnification: - DoF is extremely shallow (millimeters) - Even at f/16, DoF ≈ 2-3mm - Distribution: 1:1 (equal in front/behind)

Calculation:

Effective f-stop = f × (magnification + 1)
Example: f/11 at 1:1 → effective f/22 (for exposure)

Quick Reference Decision Tree

graph TD
A[Choose Desired DoF] --> B{Deep or Shallow?}
B -->|Deep DoF| C[Landscape/Architecture]
B -->|Shallow DoF| D[Portrait/Isolation]

C --> E[Wide lens: 24-35mm]
C --> F[Small aperture: f/11-f/16]
C --> G[Focus: Hyperfocal distance]

D --> H[Tele lens: 85-135mm]
D --> I[Large aperture: f/1.4-f/2.8]
D --> J[Focus: Precisely on subject]

G --> K[DoF: Foreground to ∞]
J --> L[DoF: Centimeters depth]

Advanced Considerations

Diffraction Limit

Physics: At very small apertures (f/22+), diffraction reduces sharpness.

Optimal aperture range: - 35mm: f/5.6 - f/11 (sharpest) - 120: f/8 - f/16 (sharpest)

Beyond optimal: - f/16: slight softening, acceptable - f/22: noticeable softening, use only when necessary - f/32+: significant softening, avoid unless DoF critical

Tilt-Shift Lenses (Scheimpflug Principle)

Effect: Tilting lens plane changes DoF plane without changing f-stop.

Use case: Landscape with slanted foreground (e.g., beach receding to horizon).

Calculation: Complex, beyond field calculation (use camera movements iteratively).

Format Comparison Summary

graph LR
A[Same Field of View] --> B[35mm: 50mm lens]
A --> C[6x6: 80mm lens]
A --> D[6x9: 105mm lens]

B --> E[DoF: Deepest]
C --> F[DoF: Medium]
D --> G[DoF: Shallowest]

E --> H[CoC: 0.030mm]
F --> I[CoC: 0.050mm]
G --> J[CoC: 0.060mm]

Key insight: Larger format = shallower DoF for same framing and aperture.

Emergency Field Tables (Memorize)

35mm Critical Values

Lens	f/8 Hyperfocal	f/11 Hyperfocal	f/16 Hyperfocal
28mm	6.5m	4.7m	3.3m
35mm	10.2m	7.4m	5.1m
50mm	20.8m	15.2m	10.4m
85mm	60.2m	43.9m	30.1m

Rule: Focus at hyperfocal → DoF from H/2 to ∞

120 (6×6) Critical Values

Lens	f/8 Hyperfocal	f/11 Hyperfocal	f/16 Hyperfocal
50mm	5.0m	3.6m	2.5m
80mm	12.8m	9.3m	6.4m
150mm	45.0m	32.7m	22.5m

DoF at Common Portrait Distance (3m)

35mm format, 85mm lens:

f-stop	DoF Range	Total DoF
f/2	2.93 - 3.07m	0.14m (14cm)
f/2.8	2.90 - 3.10m	0.20m (20cm)
f/4	2.86 - 3.15m	0.29m (29cm)

120 (6×6), 150mm lens:

f-stop	DoF Range	Total DoF
f/2.8	2.93 - 3.08m	0.15m (15cm)
f/4	2.90 - 3.11m	0.21m (21cm)
f/5.6	2.87 - 3.15m	0.28m (28cm)

Field Notes Section

Print this page and laminate for field use.

Your Lens Kit

Fill in your specific lenses and preferred apertures:

Lens	Format	Preferred f-stop	Hyperfocal @ f-stop	Notes
___mm	35mm / 120	f/___	___m	____
___mm	35mm / 120	f/___	___m	____
___mm	35mm / 120	f/___	___m	____
___mm	35mm / 120	f/___	___m	____

Quick Calculation Worksheet

Given: - Focal length (f): _ mm - Aperture (A): f/ - Focus distance (D): __ m - Circle of Confusion (C): _____ mm

Calculate Hyperfocal Distance:

H = f² / (A × C) = _____² / (_____ × _____) = _____ mm = _____ m

Calculate DoF at Distance D:

Near = D / (1 + D·A·C / f²) = _____ / (1 + _____) = _____ m
Far = D / (1 - D·A·C / f²) = _____ / (1 - _____) = _____ m
Total DoF = _____ m

Online Calculators (Cross-Check)

When in doubt, verify with: - DOFMaster: www.dofmaster.com - PhotoPills: photopills.com/calculators/dof - Cambridge in Colour: cambridgeincolour.com/tutorials/dof-calculator.htm

Best practice: Calculate critical shots before the field, note results in this guide.

Sources and Further Reading

Books: - "View Camera Technique" - Leslie Stroebel (1999) - mathematical foundation - "The Camera" (LIFE Library of Photography, 1970) - DoF principles - "Large Format Nature Photography" - Jack Dykinga (2001) - field techniques

Standards: - ISO 1233:1992 - Photography — Depth of field - Circle of Confusion standards (various manufacturers)

Compiled: 2026-05-23 Formats: 35mm (24×36mm), 120 (6×6, 6×7, 6×9) For: Field use with film cameras