Calculators·Flash photography

Flash distance for close-ups.

Calculate the optimal flash distance for macro and close-up photography – with magnification ratio and light direction corrections so exposure stays on point in the close-up range.

Works for ring flash, macro flash and system flash – whether you shoot insects, jewellery or product details.

◆Magnification ratio
◆Light direction
◆All flash types
◆Real-world tips

Flash Distance Calculator for Close-ups

Calculate the optimal flash distance for correct exposure in macro and close-up photography

Input Parameters

Flash Guide Number (m)

Aperture (f/) - effective

For macro photography, f/8-f/16 is often used for sufficient depth of field

Focus Distance Setting (m)

Focal Length (mm)

Typical macro lenses: 60mm, 100mm, 180mm

Light Direction

Side and grazing light reduce the effective guide number

Calculation Results

Important Notes:

• Formula: Distance = Guide Number ÷ (Aperture × (Magnification + 1))
• Close-ups require more light
• Side light reduces the effective guide number
• Diffusers and filters reduce light output
• Test shots are recommended for precise tuning

◆Fundamentals

Flash photography in the close-up range.

Close-up and macro photography follow special rules for flash lighting. The magnification ratio increases the amount of light you need – something the standard guide number formula has to account for.

Magnification ratio

How close is close?

The magnification ratio describes the ratio between the image size on the sensor and the actual subject size:

1:4 (0.25×): Close-up range
1:2 (0.5×): Near-macro
1:1 (1.0×): True macro photography
2:1 (2.0×): Extreme macro photography

Light direction & flash type

What shapes the quality of light.

Light direction has a significant impact on the effective guide number:

Front lighting: Maximum light output, flat look
Side lighting: −0.5 stops, three-dimensional look
Grazing light: −1 stop, strong shadows

Flash types for close-ups: ring flash (shadow-free), macro flash (two adjustable heads), standard flash (with diffuser and reflector).

◆Formula

The extended guide number equation.

The classic formula is extended by the magnification ratio – and the magnification ratio itself can be derived from focal length and subject distance.

Distance = Guide number ÷ (Aperture × (M + 1))

M = magnification ratio.

M = f ÷ (s − f)

f = focal length, s = subject distance.

Example

GN 32 · f/11 · 100 mm · 0.5 m

Magnification M ≈ 0.25 (1:4)

Flash distance = 32 ÷ (11 × (0.25 + 1)) = 32 ÷ 13.75 ≈ 2.3 m

◆Reference

Magnification ranges and applications.

A quick overview of which magnification dominates which genre – so you immediately know where your setup belongs.

Magnification	Ratio	Application	Typical subjects
0.1×	1:10	Wide-angle / normal	Landscape, portrait
0.25×	1:4	Close-up	Flowers, small objects
0.5×	1:2	Near-macro	Insects, coins
1.0×	1:1	True macro photography	Jewellery, stamps
2.0×	2:1	Extreme macro photography	Crystals, textures

◆Pro tips

Five pointers for macro flash work.

Diffusion is essential

Use diffusers or reflectors to soften hard flash light. At very short flash distances the light otherwise becomes harsh and overly contrasty.

Multiple flashes for even lighting

A main flash plus a fill flash or reflector prevents harsh shadows. Ring flashes provide even but flat light.

Adjust flash output

Start at 1/4 to 1/2 power and adjust based on test shots. Full power often leads to overexposure at short distances.

Working aperture for depth of field

f/8 to f/16 usually offer the best compromise between depth of field and diffraction blur in macro shots.

Consider focus stacking

At extreme magnifications depth of field is minimal. Plan multiple exposures with different focus planes for focus stacking.

◆Equipment

Three setups for different budgets.

From an entry-level system flash with diffuser to a pro setup with ring flash and wireless control – there's a configuration for every experience level.

Beginner