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square, out of focus highlights


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#1 F Bulgarelli

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Posted 21 August 2009 - 07:34 PM

Hello,

Does anyone know how to obtain this effect?



about 39 seconds into the trailer

It's in the movie "the Sister Keeper"

The car headlights and other highlights appear square

Could be a special iris or maybe just one of those filters with square grids,

any thoughts?

thanks

Francisco
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#2 Chris Millar

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Posted 21 August 2009 - 09:28 PM

square iris, yes.

Modify a lens (open it up and replace the iris) or at least on a Bolex both the PTL and POE zooms have a two blade design that will achieve similar effects although oriented 45deg into a diamond shape ...
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#3 Jim Hyslop

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Posted 21 August 2009 - 09:46 PM

Does anyone know how to obtain this effect?



about 39 seconds into the trailer

[...]

Could be a special iris or maybe just one of those filters with square grids,


If by "square grids" you're referring to filters like this

Posted Image

then no - those are called star filters.

You can create your own custom bokeh effects. Have a look here.

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Jim
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#4 Sherman Johnson

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Posted 21 August 2009 - 09:48 PM

Looks like it's perhaps a hard matte in the matte box... Probably a matte size that's smaller than the diameter of the front element...
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#5 Tom Jensen

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Posted 21 August 2009 - 10:00 PM

Out of focus practicals?
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#6 Chris Millar

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Posted 21 August 2009 - 10:18 PM

You can create your own custom bokeh effects. Have a look here.

--
Jim


With those you'll get out of focus effects on highlights that should otherwise be more in focus... And in all likelihood would look quite nice, but unpredictable. Basically Im saying that you can no longer trust your lens to operate/focus as you would normally.

By replacing the iris as I have suggested you'll still be able to pull focus and have expected results (to a point) - exposure you'll have to nut out either with a bit of fore-thought or experimentation.
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#7 Chris Millar

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Posted 21 August 2009 - 10:20 PM

Out of focus practicals?


I think the edges are too sharp for this - but yes its an option huh ;) - time consuming !
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#8 Richard Vialet

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Posted 21 August 2009 - 11:43 PM

Yea it seems like a hard matte on the mattebox effect.

Aren't there some anamorphic zooms and telephoto primes that have square bokeh like that as well?
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#9 F Bulgarelli

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Posted 21 August 2009 - 11:44 PM

yeah, it might be a square/rectangular iris? interesting
the thing is, they are shooting night which would have required an open or almost wide open aperture
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#10 Bruce Greene

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Posted 22 August 2009 - 01:50 AM

yeah, it might be a square/rectangular iris? interesting
the thing is, they are shooting night which would have required an open or almost wide open aperture


I haven't seen the clip, but this is usually caused by a hard matte in the matte box at wide aperture. Try making some mattes in the shape you want and experiment. You can see the effect in the viewfinder. It only shows on out of focus highlights like headlights and such.

It drove me crazy, until I figured it out, when I didn't want it:)
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#11 Satsuki Murashige

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Posted 22 August 2009 - 02:40 AM

Hey Francisco,

Here's a thread that explains the two causes: http://www.cinematog...hl=square bokeh.
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#12 Leo Anthony Vale

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Posted 22 August 2009 - 01:39 PM

The car headlights and other highlights appear square

Could be a special iris or maybe just one of those filters with square grids,


One often sees that bokeh with Cooke zooms.
Because they usually have the square matte at the front of the lens.

usually the 20-100mm, also the 20-60mm & some of the 25-250mm models.

http://www.redrental.....images/zoom2

q=tbn:9dzeGcon91YXtM:http://www.abelcine.com/store/image.php%3Fproductid%3D1001102"]http://tbn2.google.com/images?q=tbn:9dzeGc...uctid%3D1001102[/url]
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#13 F Bulgarelli

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Posted 22 August 2009 - 10:03 PM

Thanks guys, anamorphic zooms, sounds like that's the answer
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#14 Nathan Martin

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Posted 23 August 2009 - 05:59 AM

I was playing around with this effect today actually. The way I do it is to make an additional iris. I cut a piece of black card to sit over the rear element of the lens, then cut the desired shape out of the card and tape it to the back of the lens. If shooting on filM
you will need a bit of testing to check your exposure compensation
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#15 boy yniguez

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Posted 28 August 2009 - 05:29 AM

Hello,

Does anyone know how to obtain this effect?



about 39 seconds into the trailer

It's in the movie "the Sister Keeper"

The car headlights and other highlights appear square

Could be a special iris or maybe just one of those filters with square grids,

any thoughts?

thanks

Francisco


hello, francisco,
sherman is correct about the mattebox. it happens when the ac puts an 85mm mask on the mattebox when shooting with a telephoto thinking " hey the angle of acceptance of the 85mm is wider than longer telephotos so it must be fine". WRONG! the diameter of the front element has to be taken into consideration, a smaller mask actually is cutting light that's supposed to enter the outer edges of the lens thus decreasing exposure. since objects very near the telephoto lens disappear, you won't see this cut-offs in the sides of the image, only in the bokeh!

boy
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