Here are two images, of the same model, each lit with a pair of Paul C Buff PLMs (Parabolic Lighting Modifier). The PLM comes in various sizes: 51, 64, and 86 inches in diameter (130, 163, and 218cm). I’m using the largest, so its a little over seven feet across, taller than my models.
The PLM was used in a couple of ways here: the bare silver umbrella, and with a white diffusion material stretched across the front. Can you tell which is which? Answer at the end of the article.
The umbrella modifier attaches via either a speedring for compatible flash units, or an umbrella shaft for universal mounting. The umbrella shaft will leave the modifier slightly off-center; this is not a concern when using it with the front diffuser. For the bare umbrella, a speedring is advised so that the light is centered and focused properly. Speed Rings are available for Paul C Buff (including Alien Bees) and Elinchrom. One of mine is mounted to a Paul Buff Zeus Bi-Tube head, the other a Speedotron 105 quad-tube via shaft.
With the diffusion material, the PLM becomes an “umbrella box” or “brolly-box”. The effect is softer light, spread over a less restrained area. There will be fewer specular highlights. The white fabric fits over the face of the umbrella. A donut-hole accommodates the flash unit and a drawstring to tightens around the face of the flash. A second drawstring tightens around the edge of the umbrella.
The bare, silver umbrella concentrates the light from the strobe (flash). It produces a tightly focused, narrow shaft of light with sharp, pronounced falloff, creating a dramatic effects. The extreme size however, still provides shadow wrapping as long as it’s not too far from the subject. There is a lot of specularity (sparkle) that you would expect from a silver reflector. Catchlights in eyes (can’t be seen in these) show the ribbed umbrella.
So which image uses the bare umbrella? Its Image “B.”
Image “A” uses the diffusers to turn the umbrellas into umbrella boxes.
Here are what the lighting units look like:
PLMs with front diffusion fabric
Shot with Nikon D3.