dwalden
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 p.1 #9 · p.1 #9 · A good article about Broncolor Para Reflectors | |
Paul Buff wrote:
First, it is impossible to create a true parabola using rods and fabric - the more rods and panels, the closer one can get. This is because the angle of incidence varies along the flat surface of each fabric panels and thus can only produce a true parabola in the form of "spokes". It's also impossible to produce a true parabola using a single "pivot stretching point" to bend the rods. This results in an arc rather than a parabola.
Final, a true parabola - achievable only with a round shape - i.e. a spun metal reflector, i.e. satellite dish, ...Show more →
Although Paul was correct (RIP!), achieving a true parabola is probably not even a desirable result for larger reflectors. Approximations are the way to go, and help to soft/wrap the light more. True parabolas produce the same lighting effect as a Fresnel lens, in terms of light collimation (light rays shooting out in a collinear/parallel manner). But if you've seen Fresnel-based hot lights (HMI's/tungstens) used on a film set, they are pretty much *always* used with diffusion in front of them, because the light is just too specular (virtually identical to sunlight). That's because the Fresnel lens is achieving an even more "perfect" light collimating effect. So the "imperfections" of a fabric-based parabola are actually helping to *slightly* soften the light more, and produce a more desirable effect on skin, without having to rely on nylon/paper diffusion. It's also good to have a reflective fabric that has some "pebbling" or "soft" silver finish in order to give it a softer feel.
cheers,
david
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Value is a very subjective thing sometimes; it depends on how much money you are willing to spend, how useful/functional the equipment is for you in real life, and how "good" the equipment makes you feel about your work and sets you apart from others. I liked the watch example in the comment section.