kosulin wrote:
1) I managed to fill it with single 580EX (using wide panel and OmniBounce), and am getting satisfactory (to my taste) evenness of light except one exception: I am getting slightly darker area in the center. I have a feeling that this might be caused by flash or bracket preventing enough light from umbrella center. I would expect that with big strobe and 7\" reflector this effect should be much more pronounced than in my case. So, do you see something similar with strobes? The only way to avoid this is to move flash head slightly out to narrow the beam of light. Is this what you do?
Your getting \"satisfactory\" results because anything larger will produce a broader light than your small light source speedlight, even with a OmniBounce or panel. That being said, the darker center is a manifestation of the fact you are not making use of the parabolic design of the PLM and further evidence that the fresnel of the speedlight is not able to fill the box. I suspect most of the energy is coming predominantly from the center of the reflector and creating a shadow from your flash unit. If you were to use a bare bulb flash tube (found in studio strobes or Quantum flashes), light would eminate omnidirectionally to fill the box, make use of the parabolic design to collimate the light and eliminate hot spots and shadows produced by your highly directional light source.
In many ways parabolic reflectors don\'t simply even out the light but rather magnify and direct the eveness of the light source itself. Speedlights are not a very good match with parabolic reflectors. To get the most out of this modifier you will need to use a omnidirectional light source.
Good luck.
Aug 22, 2009 at 02:22 PM
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