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Book light vs Kinos, etc...


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#1 Ryan K

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Posted 16 March 2008 - 02:43 PM

Hey guys,

I was just wondering what the difference is between a book light and, say, a kino unit of similar size or a lamp being blasted through a diff frame of similar size? Is it simply to do with the fall-off from the book light being smoother? I would have thought that seeing as the effective 'source' of the book light would be the material the light was eventually coming from, the fall off would be roughly the same as the other two units I mentioned.

I'm aware that having a lamp blasted directly into a diff or silk frame can leave a hot spot, but if the lamp is position far enough back, how would the spread differ from a book light?

Many thanks in advance,

Ryan
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#2 Sean Conaty

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Posted 20 March 2008 - 01:46 PM

I'd be interested also in hearing someone weigh in on this. I'm assuming it has something to do with the fact that the book light would be much more even, less sourcy, less spotty, etc. anyone?
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#3 Michael Nash

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Posted 20 March 2008 - 03:29 PM

I'd be interested also in hearing someone weigh in on this. I'm assuming it has something to do with the fact that the book light would be much more even, less sourcy, less spotty, etc. anyone?


Assuming the same sized diffusion frame, it all depends on the density of the diffusion material. If the material is evenly lit and dense enough to not allow a hot spot, then it doesn't matter what the light source behind it is, the falloff will always be the same. With thinner diffusion material that allows a hot spot, you've basically got two light sources -- the original source, plus the diffusion material -- each with their own falloff and softness.
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#4 Ryan K

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Posted 20 March 2008 - 04:42 PM

Thanks Michael,

If they're the same, though, where is the benefit in using a book-light setup? Surely instead of having a 4x4 book-light with all the issues of inefficiency, area taken up and flagging, you could just have a couple of 4'x2 kinos with a diff frame over them?

There must be something else about them which makes them so useful, non?
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#5 Michael Nash

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Posted 20 March 2008 - 05:44 PM

When you double-diffuse light, with a very thin diffusion closer to the subject, you can get a more complex quality of light with two types of softness and falloff at the same time. The trick is to have a bit of distance between the bounce and diffusion, so that there's distance for the two different falloffs to happen. Diffusion material flat on the surface of a Kino doesn't really do that.

I talked about it more at length here, and you might also enjoy the whole thread.
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