How Can I Tell If A Softbox/Umbrella Is Truly Parabolic?

Started Sep 14, 2020 | Questions thread
MayaTlab0 Senior Member • Posts: 2,985
Re: How Can I Tell If A Softbox/Umbrella Is Truly Parabolic?

rfsIII wrote:

Is there some kind of rule of thumb or do I have to have the actual example in hand to check on its parabolicity?

A quick tip if you have an iDevice : you can take a sideways photo of the reflector from a long enough distance to avoid perspective issues, and draw a three points curve with the markup tool to follow the reflector's shape. This three point curve is parabolic by design with that tool and gives you a quick way to assess the "parabolic-ness" of the reflector.

And does the quality of being parabolic really endow any special light-throwing characteristics? S

The main advantage for me of parabolic or parabolic-ish reflectors is that they can use a slightly scattering silver material to prevent "bicycle wheel" patterns and multiple shadows while retaining somewhat decent directionality.

Personally I have no use for an expensive version of these, but I really, really like Paul Buff's older soft silver PLMs. They could combine decent directionality and efficiency with very little bicycle wheel pattern and multiple shadows effect. The newer material isn't quite as nice IMO.

All the other silver umbrellas (important note : by umbrella I mean the cheaper reflectors with an actual rod mechanism, not Bron-style paras) I've tried fail at this and the deep ones are plain stupid for plenty of reasons.

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