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Thread started 17 May 2011 (Tuesday) 07:16
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Can someone explain what a Parabolic umbrella is?

 
digital ­ paradise
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May 17, 2011 07:16 |  #1

Thanks in advance.


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eduardofrances
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May 17, 2011 07:47 |  #2

digital paradise wrote in post #12425332 (external link)
Thanks in advance.

Today what´s called a parabollic umbrella is a 16 panel umbrella that´s being offered by various vendors, these umbrellas offer a way to have a big modifier for not so much money, the discussion of wether or not these are parabolic has been ensued since these came to the market, regardless of that discussion this product has become pretty popular among many shooters.

There are tons of different parabolic umbrellas though, Profoto, Briese and other manufacturers do parabolic umbrellas that are different than the ones sold by Paul C. Buff, Viewfinderphotography or Costwoldphoto (to name a few).

I recently bought one from Costwoldphoto and I have been impressed with the umbrella packs a punch (silver version is really efficient) and it is really well made, Now is it parabolic? I dunno and also I don´t care much :P (In Spain there´s a saying that goes "soy de letras" which means I didn´t studied a math related career) All I wanted is a huge *ss umbrella for full body shots :D! And this does the trick regardless if it is really parabolic or not.

There are tons of examples shot with these umbrellas here and in Fred Miranda´s site, Google Images is going to be your best friend


http://flickr.com/phot​os/eduardofrances/ (external link) :D

  
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bdp23
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May 17, 2011 08:25 |  #3

Parabolas are technically 'conic sections'. Get a perfect cone, slice through it down to the base, the edge of the cut is a parabola.

The important thing photographically about parabolas is they have a focal point.
You put lots of light at the focal point and it bounces off all the umbrella surface at different angles, but when it leaves the umbrella ALL THE RAYS ARE PARALLEL.
(the reverse theory is used to receive satellite signals)

Why is this good?
More light reaches the subject. More control.

Also, by the time the sun's rays reach the earth (90million miles or more) any ray of light that wasn't pointing directly in our direction has veered off and completely missed the planet.
So? well, parabolic umbrellas don't cast convergent or divergent light, so the shadows are (technically) more natural like they were coming from the sun.

So it's kinda got a built-in snoot?
Yeah, I spose. But the fact true parabolic reflectors fire all the light perfectly in one direction means you have more control over it. Even if you add a diffuser, more light reaches the diffuser.


Here's the ultimate truth: Photography isn't accounting, it's art. If it looks good, it looks good. I doubt you can tell the difference between a perfect parabolic umbrella and anything reasonably close to parabolic, but you might notice your speedlite pops are a little brighter than non-parabolics (ahem, although when using ETTL the camera might just turn it down a touch to compensate!)


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May 17, 2011 08:56 |  #4

Thanks for the explanations.


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peabody2468
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May 17, 2011 10:51 |  #5

It seems to me that the focal point effect works only to the extent that the reflector is "perfect." But if the reflecting surface itself bounces an incident ray off in all directions, rather than just one like a perfect mirror would do, you're going to get a lot of dispersion. Whether a parabolic umbrella is noticeably better than a regular one is beyond my pay grade.




  
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May 17, 2011 11:38 |  #6

bdp23 wrote in post #12425570 (external link)
Also, by the time the sun's rays reach the earth (90million miles or more) any ray of light that wasn't pointing directly in our direction has veered off and completely missed the planet.

I like this explanation. When you understand the physics of light all this becomes so much easier. Tough to make well thought out purchases when you don't understand the basics, particularly on camera diffusers.


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dmward
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May 17, 2011 12:17 |  #7

PCB points out that a good parabolic umbrella reflects the light source in such a way that the rays are not parallel but that the light emanating from focused with fast fall off outside the diameter of the reflector. That's what makes the wrap possible.

What I like about parabolic reflectors is the punch they offer along with wrap to provide a smooth transition from highlight to shadow.

Here are two examples.

The model on the bike is lit with a 64" silver PLM V2 about 10 feet away. A 64" white PLM was used for fill. It was configured for shoot through with black back. it was about 5 feet away.

The second shot was with an 86" Silver PLM about 6 feet to camera left and a 64" silver PLM for fill just camera right.


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CincyTriGuy
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Sep 16, 2013 13:17 |  #8

Stumbled across this old thread and had another question. Regardless of what is and is not a true parabolic per the definition, at what point do photographers generally start calling modifiers "parabolics"? It seems like up to about 48" or so, most photographers will say umbrella or brolly, and then anything larger is called a parabolic. Is the point being that a parabolic is generally considered anything capable of lighting an entire subject?


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abbadon31
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Sep 16, 2013 13:25 |  #9

Its not based on size; its the shape and how it focus the light like a spot light


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FlashZebra
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Sep 16, 2013 18:19 |  #10

abbadon31 wrote in post #16301204 (external link)
Its not based on size; its the shape and how it focus the light like a spot light

To define the shape of a parabola and the focus specifically:

http://en.wikipedia.or​g/wiki/Parabola (external link)

A parabola is the shape generated and defined by this general equation:

y = ax
2 + bx + c (x2 is the square of x))

Enjoy! Lon


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PacAce
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Sep 17, 2013 09:05 |  #11

FlashZebra wrote in post #16301927 (external link)
To define the shape of a parabola and the focus specifically:

http://en.wikipedia.or​g/wiki/Parabola (external link)

A parabola is the shape generated and defined by this general equation:

y = ax
² + bx + c

Enjoy! Lon

There, fixed it for you , Lon. ;)


...Leo

  
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Can someone explain what a Parabolic umbrella is?
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