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Circle of confusion for 2 perf super35


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#1 James Rydings

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Posted 26 August 2008 - 02:53 PM

what is the COC for 2 perf s35mm?
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#2 Dan Goulder

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Posted 26 August 2008 - 05:39 PM

what is the COC for 2 perf s35mm?

There is no 2-perf super 35, thus the circle of confusion.
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#3 Allen Achterberg

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Posted 26 August 2008 - 06:26 PM

You need to learn to ignore what the lens is projecting its image onto, and pay attention only to the size of the image the lens itself is projecting. thats where all your DOF science happens.

So it will be the same as whatever format the lens is.
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#4 Bruce Taylor

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Posted 26 August 2008 - 08:07 PM

Interesting question. As Mr. Goulder points out, there is not officially a 2 perf Super 35 format, but a full aperture gate would give you a 2.66:1 aspect ratio with a 2 perf pulldown, if memory serves.

Mr. Achterberg's statement is true too. I am wondering if it is effective , perceived depth of field that you are after? That's going to vary with the presentation format/media/size as well as the capture media.

Or am I out to lunch here?

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#5 Patrick Neary

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Posted 26 August 2008 - 10:13 PM

what is the COC for 2 perf s35mm?


Panavision's cool little calculator uses 0.001" for all of the 35 DOF calcs, so I would guess it would work for 2-perf as well.
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#6 James Rydings

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Posted 30 August 2008 - 02:49 PM

We are shooting Panavision 2 perf super 35mm. Our aspect ratio is 2.40:1. I dont know what size the gate is, but there is no room on the sides, and very little room on the top and bottom. Of what I do understand about circle of confusion, I realize its in reference to the size of the image being projected, not the size of the image being recorded. However seen as a smaller part of that image being projected is being recorded, and then blown up, wouldn't that decrease the depth of field. The DP seems to think it is increasing our depth of field. Pananvision however has told me the COC is 1/2 1000 of an inch, which is therefore a smaller depth of field than standard 35. Anyone have any ideas?

Edited by James Rydings, 30 August 2008 - 02:51 PM.

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#7 Mitch Gross

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Posted 30 August 2008 - 09:39 PM

THe more you need to magnify the image, the smaller the CoC needs to be. A 35mm anamorphic shoot uses far more negative so it will therefore have a larger CoC than spherical 35mm. Likewise, Super-35 which is spherical but will be magnified to a widescreen anamorphic projection -- which generally is a projection larger than a spherical one -- has a tighter CoC. 2-perf is quite close to the negative area of Super-35 when finished to anamorphic print, so you can probably go with this.

It's this same numerical theory that claims that HD lenses for 2/3 cameras must be 2.5 times sharper because they need to yield a tighter CoC. In reality it's all a bit of hokum because the projection size for any of these format is never a constant. You can project a 1.85 image far larger than a 2.40 image if you choose to. On a 4:3 TV the 2.40 image within a letterbox has an effectively huge CoC because the image is so small. Possibly the only place where a dead-on accurate CoC can be applied is in closed-loop systems such as ride films or IMAX, where the exact projection standards are known quantities from the outset.

All this goes to say that you can use your regular 35mm CoC guides for depth of field calculation without concern.
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