Or: Why your flash doesn’t illuminate “the whole room”
Now it’s getting a bit physical – but don’t worry, you don’t need a collection of formulas. What you do need is a feel for how light behaves, especially when you have it in your own hands.
Because when you work with flash, you are suddenly the light maker. And unlike the sun, which is millions of kilometers away and still illuminates us evenly, you are often only a few meters or even centimeters away from the subject with your flash.
And that’s what matters.
Light decreases with distance – drastically
A common misconception:
“My flash is powerful enough, I just use it to make everything bright.”
Does not work. This is because light has the (admittedly somewhat nasty) property of not decreasing linearly, but quadratically.
This is called the reciprocal square law – sounds cumbersome, but it means something in everyday life:
If you double the distance to the subject, you only get a quarter of the amount of light.
Example:
- 1 meter distance → 100 % light
- 2 meters → 25 %
- 3 meters → approx. 11 %
- 4 meters → only 6.25 %
That’s why the flash on a concert photo only illuminates the first two rows – and everything behind it disappears into darkness.
Flash object camera: three distances, one image
There are two important distances that you need to keep in mind:
- Distance from the flash to the object
This influences how bright the light is on the object – and also how soft or hard it appears. - Distance of the camera to the object
This changes the image section and the perspective, but not the light intensity – as long as the flash is not mounted on the camera.
Important difference: If you move closer to the subject with the camera, the light remains the same – unless the flash has “moved” with you (e.g. with on-camera flash).
When is lightning “too far away”?
- If your flash is so far away that hardly any light reaches the subject, you have to increase the power considerably – which in turn leads to harder light.
- Or you notice that the background is suddenly brighter than your main subject – because the flash barely reaches the subject but touches the surroundings.
Rule of thumb:
The closer the flash is to the subject, the more efficient, softer and more controllable the light is.
Using the effect of light creatively
If you know the behavior of light, you can use it consciously:
1. soft light through proximity
- Flash with softbox directly on the subject → beautifully soft, flattering light
- The background remains darker as the light falls off quickly
2. dramatic looks through distance
- Flash further away at full power → hard, directional light, sharp shadows
- More of the room is illuminated – sometimes intentionally, sometimes disruptively
3. isolate motif
- Flash close to the subject, exposure set to the flash → the rest of the scene is underexposed
- Ideal for people or street photography with punch – see Bruce Gilden
Shooting ideas for the light fall-off experience
Test 1: Portrait with close light source
- Flash 50 cm away, soft light shaper → subject lights up, background disappears into darkness
Test 2: Same setup, flash 2 m away
- Same camera settings, but the flash is less noticeable
- Solution: Turn up the flash output – but the light becomes harder, the background brighter
Conclusion: Proximity is power
Flash photography is not just a question of technique, but of position. Once you understand how much light changes with distance, you can control your light precisely and creatively.
So go ahead and take a few steps closer. Your flash – and your subject – will thank you for it.
