An overview of possible f-stops at a distance of 15 meters (49 ft).

Measured distance 15 m – outdoor (no room reflection etc.)
ISO 100, 1/250 s (no measurable interference caused by ambient light)
Porty L 1200, EH Pro Mini 1200 Head, full power

Click here to see the table of light formers (PDF, 41 KB)

We just measured some common reflectors to give you a rough guideline. The values approximately relate to other construction forms. Data of all reflectors and a nice table comparing the different lighting characteristics can be found at our light former comparison.

Light intensity decreases with the square of the distance, so the best solution is always: Place the light sources as close to the subject as possible! This increases the light output and limits straylight. Instead of using a large softbox over a huge distance, it’s better to go for a smaller one from a short distance.