Parabolae, hyperbole, and the parabolic paradox

Parabolae, hyperbole, and the parabolic paradox

Sorry – I couldn’t resist that as a title – and it lets me pick up on a Karl Taylor rant I saw on YouTube about parabolic softboxes.

Now, I’ve written about a parabolic brolly, and I like it: and that’s unaltered by the rant. A parabola can be a very useful thing, photographically, and if you go back to the physics and ray diagrams you’ll see why – a sort of spotlight effect. If you use a parabolic reflector, you’ll see the benefits of that narrow beam, giving a bright, sparkly sort of light, with the rays more or less parallel. Often, there’s a way of adjusting the position of the flash unit inside the reflector to get the best focus: in the largest Broncolor units, that’s motorised!



The crucial thing is which way the light source is facing inside the parabola. If it’s facing into the reflector and away from the subject, with no baffles or internal panels, it’s a reflector, and a scrim across the front is a courtesy detail, making the light a bit softer. But if the flash is at the back, facing forwards (possibly with a couple of baffles and a scrim at the front) it’s just a softbox, and (within fairly wide limits) the depth doesn’t matter. The sides are simply there to stop light going all over the place sideways – the baffles soften it, soften it and soften it again.

Why is the difference between a reflector and a softbox significant? Well, one reason is that a parabolic softbox will probably be bigger and heavier than a more conventional light modifier – and with large sizes, we’re talking serious inconvenience getting it in and out of rooms. I have a large octabox, which is slender by comparison, and gives beautifully even light – but it feels a bit on the big side for an Edwardian semi. No chance in a small terraced house with low ceilings! There may also be a bit of a difference in cost – my parabolic reflector brolly cost under £20, but a similarly-sized parabolic softbox will cost around ten times that, and maybe more, depending on the brand.



The Yves Saint Laurent book in the picture is for sale, by the way, complete with slip cover and posting box – please make me an offer if you’re interested. Its purpose here is to help show the soft but directional light that the reflector gives when it’s close in to the subject.

The lead image shows you about as much as you need to know about the structure of the reflector, though it’s interesting that the ‘handle’ is very short when folded down, and you have to take the light off the stand to put the stand through the zippered slit at the bottom of the device. There’s a diffuser to attach over the front if the brolly, totally enclosing the flash unit, and softening the light a bit further – but sheer size makes for a good deal of softness (along with the brightness that the shape gives.