Tuesday, 16 September 2014

How to get soft diffused light out of small flashes and strobes

In the previous article about fill in lighting we discussed that the best choice of lights to act as fill are big soft lights. Now in this article let us see how we could convert our tiny little flashes and strobes into really huge light sources producing soft light which wraps around furniture and fixtures producing little or no shadows.

Hard Light Vs Soft Light

Shadow produced by hard and soft lights
Shadow produced by hard and soft lights

We judge a light as hard or soft based on the definition of the shadows. If the edges of the shadows are well defined (like a chiseled edge) we call the light hard light 

hard light
Hard light

and if the edges are soft and the dark areas gradually turn to light (like a gradient) we call the light soft light.

soft light
Soft Light

Factors that affect the Quality of Light

There are two factors that affect the quality of light they are:

1. Size of the light source in relation to the subject and
2. The distance of the light source from the subject.

Well actually the two points given above are just one and the same, it is not the size of the subject or the size of the light source that matters; it’s the relative size of the light source i.e how large or small the light source is when compared to the subject. If the light source is tiny when compared to the subject result will be hard light with well-defined shadows and a lot of contrast. And if the light source is huge when compared to the subject we will have soft lighting which wraps around the subject producing much less contrast and soft shadows.

Then why did we put it up as two different points, the reason is simple, no matter how large a light source is, the farther it gets from the subject, the smaller is its effective size and thus the harder the light gets. A good example to illustrate this point will be Sun. we all know that sun is a gigantic light source which has a diameter of thousands of miles, but still sunlight on a bright sunny day is hard, it is because sun even though a very large source is thousands of kilometers away from earth. Now let us consider what happens to sunlight on a cloudy day, we all know for a fact that sunlight on a cloudy day is soft. This happens because the clouds above acts as a giant diffuser, softening the sunlight. The clouds now become our new light source, which is large and is not that far away…. Result… soft, diffused light.

Increasing the Effective Size of Light Source by Bouncing Light off Walls and Ceilings

The simplest way of converting our flashes and strobes to huge light sources is by bouncing them off walls and ceilings. Turning your light to the opposite direction of your subject and making the light bounce off some surface (walls or ceilings) will allow you to create a light source several times bigger. The farther the light is from the surface from which light is bounced the greater will be the effective size of light (lesser will be the power, so you’ll need to increase output) if you have the room to move the light several feet from the surface you can effectively create a light source which is as big as the wall or the ceiling (the wall or the ceiling is now our light source).

Take a look at the images given below, the first one is taken with the flash 12" (1 foot) from the wall, notice the size of the highlight area.

bounce flash tips
bounce flash tips

Now see how the highlight area enlarges as we move the flash back. The flash is now at 36" (3 foot) distance from the wall. The further we move the flash away from the wall the larger the highlight area becomes (which is now the effective size of our light).

bounce flash technique
bounce flash technique

Some Practical Tips

Always remember that light catches the color of the surface from which it bounces back. So bouncing lights work well in case of white walls and ceilings but one needs to be careful when bouncing off colored surfaces.

When bouncing flashes it is better not to deploy the wide panel as it causes the light to travel in a much wider angle (approx. 14mm) and as a result in certain situations some direct light might enter the scene.

Similarly when bouncing strobes use the standard reflector or even a small softbox with the outer diffusion panel removed. The diffusion panel will ensure even more diffusion but at the loss of a lot of light.

Other Light Modifiers

Umbrellas, both bounce and shoot through, softboxes etc could all be used to modify our light source. But there is one particular modifier that requires special mention. For architectural and interior photography a scrim could be a very handy tool to have. Apart from its main use as a very large diffusion screen, It could be used to cover doors or windows to make the light coming from it very soft, it could even be used as a huge reflector if need be. 

DIY Diffuser Scrim made of pvc pipes in action
DIY Diffuser Scrim made of pvc pipes in action

The picture given above shows our 12 foot by 8 foot diy scrim in action.  It is made of pvc pipes and fittings and it uses the lee filters 460 grid cloth as the diffusion material. As you can see the ceiling there is not ideal for bouncing lights and the back wall is simply too far. The large scrim produces light unlike any other.

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