Why does light fall off across a scene?

Due to the inverse square law, objects further from the light receive less illumination. In a scene 2m deep with the light at 2m, the back (4m away) receives only 25% of the front illumination -- a 2-stop difference. This is why groups and products can have uneven lighting.

How do I reduce light falloff?

Move the light further from the scene. At 2m with 2m scene depth, falloff is 2 stops. At 6m with the same 2m depth, falloff drops to 0.5 stops. The trade-off is you need more flash power at greater distances. Alternatively, use multiple lights or reflectors to fill the back.

Can I use falloff creatively?

Yes. Deliberate falloff creates depth and drama. Placing a light close to a subject creates rapid falloff, darkening the background naturally. This is the basis of many moody portrait and food photography lighting setups. The key is controlling falloff rather than fighting it.

How does this apply to group photography?

For even illumination across a group, the light should be at least 3-4 times the depth of the group away. For a 2m deep group, place the light at 6-8m. This reduces falloff to under 0.5 stops. Use large modifiers to maintain soft light quality at this distance.

Light Falloff Calculator -- Intensity Across a Scene

Calculate light intensity drop-off from front to back of a scene using the inverse square law.

Light to Front of Scene

Distance from light source to the nearest subject

Scene Depth

Distance from front to back of the scene

Flash/Light Power

Flash power in watt-seconds for guide number estimate

Shoot Scenario

Different scenarios have different evenness requirements

How We Calculate This

This calculator applies the inverse square law across a scene:

Intensity at Each Point

I = I_front x (d_front / d_point)^n

Falloff in Stops

Stops = n x log2(d_back / d_front)

Where n is the falloff exponent (2.0 for standard inverse square law). In practice, large modifiers and reflected light can reduce the effective exponent below 2.0.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.