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Parabolae, hyperbole, and the parabolic paradox


Time for an update: I still use film, though. Not vast quantities, but I have a darkroom, and I'm not afraid to use it.

I enjoy every image I take: I hope you'll enjoy looking at them.
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Parabolae, hyperbole, and the parabolic paradox

14 Dec 2020 8:13AM   Views : 388 Unique : 281


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.


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dudler Avatar
dudler Plus
20 2.2k 2063 England
14 Dec 2020 8:17AM
Of course, this kind of thing is much better demonstrated with a model in front: but with Level 3 precautions, that's not currently possible. But if you look back to my nude* of Aimee HERE you'll see how nicely the light works on a three-dimensional subject.

* 'Nude' is old-fashioned code for 'NSFW' or 'not office friendly' for those unused to archaic terminology.
saltireblue Avatar
saltireblue Plus
13 14.8k 92 Norway
15 Dec 2020 9:17AM
There's one word missing from the blog title, John:


Isaac Hayes
dudler Avatar
dudler Plus
20 2.2k 2063 England
15 Dec 2020 12:14PM
But I’d need a picture of Julie Andrews...
saltireblue Avatar
saltireblue Plus
13 14.8k 92 Norway
15 Dec 2020 1:34PM

Quote:But I’d need a picture of Julie Andrews...

I think you are thinking of supercalifragilisticexpialidocious, John...Wink
Isaac Hayes' song is more my taste than Ms. Andrews.Wink
dudler Avatar
dudler Plus
20 2.2k 2063 England
16 Dec 2020 6:51PM

That's my lack of musical breadth showing...


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