Light Loss with Translucent Fabric

The first step in this lesson is to set up the RUD umbrella onto the studio strobe unit we have chosen for the lesson. We set the power of the strobe to 300 watt/seconds or, for this unit, 1/3 power.

It is important that you choose the proper reflector for this purpose to maximize the output of the light source. To illustrate this, we will first use a translucent umbrella that allows light to both bounce off and pass through. Once we had the light put together, we positioned it at a 45-degree angle on the set. We then set up a white LiteDisc reflector opposite the umbrella on the set (figures 1 and 2). We will not touch the LiteDisc for the balance of the lesson. It is there only to help us see all the effects of our light changes.

With our lighting in place for the first shot, we used the light meter to get our base starting exposure, 1/60 @ f/11 (figure 3). We set the camera according to the meter's reading and made our first shot.

In figure 4, we see a clean look. The bounced light off the RUD umbrella has rendered a soft look to our subject and the cast shadows.

Umbrella efficiency is measured by the amount of light that is reflected or bounced. When we employ a white translucent umbrella, we are using an inefficient light because much of the light is passing through and not bouncing back onto the subject.

In the following figures we made some light meter readings behind the umbrella to show just how much light is lost through the umbrella (figures 5 and 6).

As you can see from our meter reading, 1/60 @ f/16, we are loosing at least as much light out the back of the umbrella as we are bouncing onto the subject.

This loss of light means loss of depth of field as you open up the aperture to reach the proper exposure level or the increase of the power out put of your light units to make up for the light loss. It also can cost dollars and cents as you are using more power than is needed and applying more wear and tear on your equipment, slowing down the shoot waiting for the lights to recycle.

Light Control with a Black Cover

To improve the efficiency of the lighting for this shot, we replaced the white umbrella with a our RUT umbrella. The RUT is the same basic product but with a black removable cover that fits over the backside of the product. Without moving our light, we first switched off the modeling light for safety, then removed the white umbrella and installed the RUT with its cover in place (figures 7 and 8).

We made some major changes to our lighting set up, so we took another meter reading (1/60 @ f/11.7). As you can see, we have gained 1/2 a stop more light by changing the umbrella to a more efficient product. We made our changes to the exposure settings and shot the next image.

Our results in figure 10 show very little change. The bounce light from the umbrella has a clean, soft look, and we have improved the softness of the cast shadow and the wrapping effect of the light around the subject.

In the next few figures, we checked the light at the back of our umbrella to see how much, if any, light was coming through. We took a reading from the back with the cover in place and found we cut the light loss by 4 1/2 stops, (from f/16 1/2 to f/3.5 1/2) (figures 11 and 12).


However, this has not completely translated to the subject because the black cover has acted as a light sponge absorbing some of the light rather than bouncing it back onto the set.

Light Control and Efficiency with Laminated Fabric

For our last improvement to the lesson, we replaced the RUT umbrella with an ADW umbrella.

The ADW is an adjustable umbrella with a very efficient laminated white reflective surface. In a later lesson we will go into the shape adjustability of this product.

Again, after switching off and without moving the light, we replaced the RUT with the ADW umbrella (figures 13 and 14).

Again, since we have made changes to our set and lighting, we took a meter reading on the set, 1/60 @ f/16.0 (figure 15).

We found that we have gained about another 1/2 stop light due to the more efficient surface of the ADW umbrella. So we made the changes to the exposure setting and shot our last result shot (figure 16).

Again, we do not see many changes to our results on the subject, but we have improved the softness of the cast shadow. This again shows how the efficiency of the reflector broadens the light pattern giving us an improved wrapping effect.

So that we can fairly compare the efficiency of the ADW, we will take readings from the back of the umbrella to see how much light loss the ADW has (figures 17 and 18).

We see that we have cut the light loss by another stop by using the ADW umbrella, and we saw this on the efficiency of the ADW in lighting the subject.

All this may seem unimportant, but you will find that using the right tool for the job will improve your results, as we have illustrated in this lesson. And you can extend the life of your lighting gear by applying these principles when you set up your shots or get ready to buy new gear.