Bounced Flash

When using bounced lighting we are trying to use the available surrounding surfaces to diffuse and redirect the light similar to moving the flash off camera with a light modifier. The light will behave more like off camera flash in a softbox!

There are several things to keep in mind with bounced lighting.
First, not all of the light will ever contribute to the exposure. It just bounces away.
Secondly, the further the light has to travel, and the more surfaces it must reflect off of on it's journey, the weaker and softer the light will be.
Third, the color of the surface the light bounces off of will color your light similarly as well as weaken the output.
our goal is soft light, so we need to control the spill light that might directly hit the subject.
And lastly, 
the angle of the flash head matters. The idea of "just point it up about 45 degrees" is not always going to work well.

IMO, this control of the spill light often requires the use of either a bounce card or a flag. A bounce card is reflective and redirects the light, a flag is dark and blocks the light. I usually prefer a bounce card because I have a greater potential to utilize the flash output as opposed to wasting it. Remember, almost everything we are doing is going to make the flash work harder.

Your external flash probably has a built in bounce card. That little white panel. IMO, that's pretty useless. It's too small and it is often in a position which isn't helpful or is even harmful. You need something better. I like the small Rogue Flash Bender because it can be shaped to direct or focus the light it bounces. Black fabric can be stuck to it if I just want a flag; I usually just attach it "backwards" instead. 

 Or, you can make your own for pennies ala Niel Van Niekerk's "black foamie thing". Use black craft foam board for a flag, or white craft foam board for a bounce card.

Forward Bounce



In all of these examples I am showing a rather wide flash zoom as would happen automatically if we were using a wider lens and didn't override the behavior. I am also showing a rather short subject distance. (the yellow shaded areas are primarily non-contributing and wasted flash output).

Here with normal forward bounce (~45* flash head angle) we have several issues as shown in the first frame. The first is that much of the spill light will hit our subject directly, we may not want that because it will minimize/counter the effect of the bounce. To fix that we can add a flag or bounce card as shown in frames 2 and 4. The use of a flag as in frame 2 will block the spill light. If we add a bounce card as is traditionally done (or use the built in bounce card), we simply add more direct lighting as shown in frame 3. If we use a bounce card as shown in frame 4 we redirect the spill light to make use of it and reduce the flash power required.

The second problem is that much of the light that will be bouncing onto our subject will be rather vertical due to our distance to the subject. This is likely to cause unflattering shadows. To change this we can reposition ourselves and change the flash head angle.

A third potential problem here is that much of the light being generated is going to be contributing to the ambient due to the subjects proximity to the back wall. To change that we can change the angle of the flash head or the subjects position. But maybe it's not a problem because it is working as a softer secondary rim light/hair light.

There really isn't a single formula that will work best, and our goals may be different for each subject. You just have to experiment a little.

Vertical Bounce


Here we have switched to vertical bounce in order to reduce the amount of light which will be adding to the background and bouncing back at us.

In frame 1 we have almost completely wasted the flash. This would only work in a small room with a powerful flash. Obviously, we could have chosen something less than completely vertical.

By adding the bounce card we will get back a good portion of the flash output, but we haven't really changed the "verticality" of the light. In fact, we may have made it worse.

To the rescue..

Backwards Bounce

By bouncing the flash behind us we fix both the issue of spill light and the verticality of the light as shown in frame 1. But we have introduced two new potential problems. First, there is a portion of the spill light bouncing off the ceiling that will travel less distance than the rest of the light. This could add secondary catch lights etc, or if the distance to the back wall is far enough it may add the only catchlight. If we find it undesirable we can lower the flash head angle as shown in frame 2 (or flag it).

The second issue is that we are wasting a lot of light output. To help with this we can add a bounce card. In this case we can add it either above or below. By placing it above we minimize the amount of non-contributing light output. By placing it below we reduce the losses and increase the directionality of the light. 

Sometimes, the distances the light has to travel is just too much for the flash. This is why they keep making stronger/better flashes such as the Nikon SB-900 and the Canon 580EX. And sometimes even they can't supply enough power.

And then there's the "softness" backwards bounce creates. Backwards bounced flash can be too soft; to the point of being "flat" with no directionality.

There are simply limits to what can be done with on camera flash.

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