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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 02 Jul 2015 (Thursday) 05:28
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How much parabolic are parabolic light modifiers ...

 
Ulysses01
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Jan 23, 2016 14:27 |  #46

absplastic wrote in post #17868535 (external link)
My conclusion is, that while the RB-120 is a great deal and a fantastic light source when used as intended, I don't see any reason to adapt it for indirect mounting or focusing. It's simply not parabolic enough to have a focal point and function like a Broncolor para 133. I'm going to revisit my idea of making a fully DIY deep parabolic.

No, but we figured as much, based on your informal examination of the shape of the Ricebowl, as mentioned in your earlier post.


absplastic wrote in post #17868535 (external link)
The one thing I would like to try with the RB-120--since I find that the Broncolors are the most magical when defocused to the point where they are a large ring light source--is replacing the inner white diffusion screen with a round silver reflector (homemade or a popup disc type), ideally black on the non-silver side, snapped in place of the diffusor with the silver side facing the strobe at the rear. If I can get all the light coming from the outer rim of the softbox, perhaps it will have a similar look to the Bron?

I'm curious. Why would you build your own when there are some good tools readily available? Is it for curiosity's sake? The bold adventure of it all? The mountain you need to climb? :-)




  
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absplastic
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Jan 23, 2016 15:18 |  #47

Ulysses01 wrote in post #17869844 (external link)
I'm curious. Why would you build your own when there are some good tools readily available? Is it for curiosity's sake? The bold adventure of it all? The mountain you need to climb? :-)

Cost. A Broncolor Para 133 is about $3000, and the Briese equivalent is more than twice that. The only affordable true focusable para that I know of is the Fotodiox 88" at $800, which is way too large for location shooting. Other solutions like the indirect mount for the Westcott Zeppelin look the part, but as you can see from the shape analysis of these cheaper softboxes in this thread, they are not parabolic. I have a Cheetahstand Ricebowl 120 and my own testing showed me that moving a light back and forth along the axis of the rice bowl does not give the effect of a focusable parabolic, it only results in a uniformly hard light. Interesting, but not the effect I'm looking for. I'm experimenting now with other ways to modify the ricebowl to get a unique look, I'll be posting about it in the DIY section shortly.


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PhilF
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Jan 24, 2016 14:15 |  #48

absplastic wrote in post #17869899 (external link)
ape analysis of these cheaper softboxes in this thread, they are not parabolic. I have a Cheetahstand Ricebowl 120 and my own testing showed me that moving a light back and forth along the axis of the rice bowl does not give the effect of a focusable parabolic,

That sucks. I actually emailed the owner of cheetahstand when the RB thread started in this forum and told him about the idea of using the RBmodifiers as indirect and focusable paras and he strongly suggest to get the Broncolors. I was a bit of dissapointed thinking RB modifiers were the inexpensive replacement to the pricey paras.


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nixland
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Post edited over 3 years ago by nixland.
     
Mar 04, 2016 18:39 as a reply to  @ absplastic's post |  #49

Well, first of all, the light spread of a speedlite even with dome diffuser is still not evenly spread enough (to the front, side and to the 45 degree back).

From my test results, the the Canon 580EXII with the dome gives 1 1/3 stop less light to the side and 2 stop to the 45 degree back.

I did a test on my Rime Lite 120cm and you can see the result below. From the look and the design of the modifier I just guess that it could be similar to the Rice Bowl, but only Scott can confirm this :)
As you can see, with barebulb strobe, we can have a ring light effects if the strobe at a defocus position. BUT, yes, it's a very weak ring light effects :)
Using speedlite will give even weaker effects.

By the way, the focus and defocus effects are work great on my Rime Lite 180 and SMDV 110. I will post the result later, including the effects on model's face.
And if my assumption is right about similarity between Rime Lite and Rice Bowl, the RB180 can give the same effects too.


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nixland
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Mar 04, 2016 18:44 |  #50

I use this mount so that 45 degree light to the back is not blocked at all.


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nixland
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Mar 04, 2016 18:50 |  #51

This is the focus and defocus effects on SMDV 110.
From the side, the SMDV 110 rod curve is close to parabolic, but unfortunately it only has 12 rod and that makes the reflective surface uneven and gives a "bicycle frame wheel" light to the front :)


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absplastic
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Mar 04, 2016 19:17 |  #52

Hmm, so maybe worth repeating my tests on the RB-120 with an actual strobe head? I could do that. The results you're getting are an improvement over what I saw with the speedlite, but they still have a pretty significant hotspot in the center that you can get rid of with a Broncolor para. It's because these parabolic-like softboxes are quite a bit flatter across the back (more spherical) than a parabolic shape, so light from the flash bounces straight back no matter where the bulb is along the center axis. Perhaps a small blocking disc or cup could eliminate this?


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nixland
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Mar 04, 2016 19:42 |  #53

absplastic wrote in post #17923869 (external link)
Hmm, so maybe worth repeating my tests on the RB-120 with an actual strobe head? I could do that. The results you're getting are an improvement over what I saw with the speedlite, but they still have a pretty significant hotspot in the center that you can get rid of with a Broncolor para. It's because these parabolic-like softboxes are quite a bit flatter across the back (more spherical) than a parabolic shape, so light from the flash bounces straight back no matter where the bulb is along the center axis. Perhaps a small blocking disc or cup could eliminate this?

Agree with you. I am thinking the same way of blocking the center area. Good luck :)




  
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Mar 24, 2016 06:54 |  #54

Hello there. Very interesting thread. I did some testing with speedlights in one 146cm parabolic silver umbrella and created this cheatsheet on my blog (flopix.de):

http://flopix.de …rne-parabolreflexschirme/ (external link)

Direct link to the image:
http://flopix.de …6/03/146cm_PLM_​flopix.jpg (external link)

Maybe it's interesting for you. I also started experimenting with various parabolic umbrellas. I have no studio strobe or bare bulb flash so I can't test these umbrellas with other light sources (maybe someone can donate me one cheap barebulb flash for testing :-P).

So I ended up with a four square flash bracket and 4 speedlights. I tried different positions for the focus effect like the true Briese or Broncolor system.

At the moment some other users joined the club on the German forum and discussing about these modifiers: http://www.dslr-forum.de/showthread.ph​p?t=1624857 (external link)

I just want to share with you my experiences.


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nixland
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Mar 24, 2016 08:01 as a reply to  @ Ultrazauberer's post |  #55

Thanks for the contribution.
Any kind of parabolic or "looks like" parabolic modifiers are welcome :)
Speedlite are welcome too, so that we can find the tips or technique to get the best way possible.




  
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nixland
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Mar 24, 2016 08:13 |  #56

CononMK has released their para with focusing rod included.

http://flashhavoc.com …bolic-softboxes-released/ (external link)




  
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DetlefG
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Mar 24, 2016 18:01 |  #57

Hello all,

I´m a German based photographer which is also infected from DIY Para solution.

In the past I played mostly with Auroa deep octa and the rimelite Grandbox (you get an rebranded Version in Germany from mikrosat) .

From time to time I has the opportunity to work with the Para and I have to say, The light of my DIY solution is realy good, but not as good as the original Para.

-- > Therefore im searching for more parabolic SB.

And it seems at the moment; you can find more and more. (like the http://mikrosat.de …krosat-Para-Dise-120.html (external link))
But I would like to verify upfront the parabolic shape which seems the way from nixland is very easy.

@ nixland,
What tool you are using for calculation he parabolic shape.

Thanks for your help
Detlef

If some one is interested about my DIY para, you can find a document under this link:
http://www.schwarzweis​sart.de/ebook/ (external link)




  
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PhilF
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Mar 24, 2016 18:15 |  #58

nixland wrote in post #17946768 (external link)
CononMK has released their para with focusing rod included.

http://flashhavoc.com …bolic-softboxes-released/ (external link)

I saw this in Ebay... $350-$400 for a para....not bad.


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Mar 24, 2016 19:40 |  #59

PhilF wrote in post #17947387 (external link)
I saw this in Ebay... $350-$400 for a para....not bad.

If it works anything at all like a Para 88, it's a good deal.


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nixland
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Post edited over 3 years ago by nixland. (2 edits in all)
     
Mar 24, 2016 22:40 as a reply to  @ DetlefG's post |  #60

Thats interesting. Thanks for sharing.
It will be more accessible if you can write the English version :)

Previously I use the tools on the link in my first post, but unfortunately the content has changed.
I found the alternative link to draw a parabola curve in here :

http://mscir.tripod.co​m/parabola/ (external link)

But you have to download the app.

It needs more image editing to overlay the curve to the para modifiers image :)




  
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How much parabolic are parabolic light modifiers ...
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