Flash Photography - Part 6

O.K. - so with the camera on f8, 1 metre away from the subject. One strobe at either side, also 1m away from the subject and on 1/8th power, we have this...


Let's move the camera away twice the distance...


No change there. Let's change to a longer lens and, still this distance away, zoom in and shoot ...


Great. Still no change. So, let's take the camera back to being only 1M away from the subject and move both the strobes to two metres away...


Wow. That got a response. So the power of the strobes dropped by half according to the distance. So if we take the strobes up to a quarter power ...


... we're nearly back to where we started.

So while the distance from the camera to the subject doesn't have any effect, the distance from the strobes to the subject certainly does; roughly double/half the power with half/double the distance.

So ... the notebook now reads ...

One strobe, f8 1/4 at one meter.
Two strobes, f8 1/8 at one meter.
Feather light, lose a stop.
Difuse cap, lose a stop.
Strobe distance is relational to power.

Of course, different strobes have different power values, so your starting ratios are likely to be different to mine. Also, if you have more than one strobe, use your light meter to calculate the stop difference between them. Part 7.