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Correct Speedlight Axis in Umbrella or Softbox

Here is a picture of a typical speedlight with an umbrella, and almost always, the speedlight is mounted far above center axis, um, just wrong, wrong I say....

flash-umbrella.jpg

And this is how it should be!

closeup-speedlight-axis.jpg

Ok, why is this wrong? Simple, the light leaves the flash, and bounces off the umbrella, but at an angle equal to which it hits. If you are going to bank a billiard ball off the side, you know its going to bounce off opposite angle that it hits.

Here is a simple diagram:

angle-reflection.gif

Now I am not going to dive deep, or even shallow into this, but your umbrella is a parabolic, its a curve, so as to direct any bounce of light to the same place. Here is a diagram of this:

light-reflected-parabolic.gif

Now, how does this relate to your umbrella and flash being off axis, take a look and my crude, bad line drawing over a photo. Since the flash is off axis, the light rays do not bounce like we think they are, they are bouncing to somewhere else.

wrong-speedlight-axis-diagram.jpg

Now this is just all silly theory right? So lets put it to the test.

Here is a shot of the flash off axis, and a shot of same setup pointing at the wall.

wrong-speedlight-axis.jpg

exampple-speedlight-off-axis.jpg

Great, lights on the floor, but the umbrella is pointing directly at the wall, not up, not down, but straight at the wall!

So lets take a look at an on axis flash setup:

correct-speedlight-axis.jpg

example-speedlight-on-axis.jpg

Tada! Light is right where we thought it would be! Directly at the wall, where we are pointing our umbrella.

Ok, so you want a real world example, and not just me playing in front of the sliding door blinds....

Take a good look at where the umbrella is pointing, and the big spot of light on the floor!

Little-Lynn-DTLA-Mazucci.jpg

Mike Bradley

Author: Mike Bradley

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