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Anamorphic FOV with Red Dragon

anamorphic red dragon arri alexa fov

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#1 Alex Stone

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Posted 01 August 2016 - 11:56 AM

I'll be shooting a short soon and we're planning on using a Red Dragon at 6K with a set of Hawk C-Series anamorphics.

 

I'm aware that, due to the aspect of the Dragon sensor, the resulting field of view using any given lens will be narrower than if it were shot with a 4:3 sensor such as on the Alexa.

 

The widest focal length in the C-Series is 40mm, which on the Alexa would produce an image with a roughly equivalent FOV that a 20mm spherical might on Super 35.

 

My question is, roughly how wide would the 40mm anamorphic appear when using the Dragon? I'm trying to work out if the 40mm will be wide enough for my needs.

 

The reasons for choosing Dragon is for maximum resolution, given that it's a vfx heavy sci-fi. Would it be better to shoot on Alexa for maximum FOV? Or try using a set of diopters?!


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#2 Alex Stone

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Posted 01 August 2016 - 01:12 PM

Ignore the comment about diopters; brain fart. Close focus is 1 metre on the C-Series and is another consideration I'm thinking about.


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#3 Alex Stone

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Posted 01 August 2016 - 03:46 PM

I've made a graphic to illustrate my question - and in doing so, answered it myself.

Posting here for others to see and perhaps learn from in the future if they were searching for the same thing.

 

A x1.13 crop isn't nearly as severe as I anticipated.


Edited by Alex Stone, 01 August 2016 - 03:51 PM.

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#4 David Mullen ASC

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Posted 01 August 2016 - 04:33 PM

Yes, you basically just use the two vertical height dimensions to calculate the crop factor.

Also, there is a 30mm and 35mm C-series lens.
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#5 David Mullen ASC

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Posted 01 August 2016 - 08:04 PM

Actually I calculate the crop factor to be only 1.11X using the vertical height figure of 17.5mm for 35mm anamorphic print projection area and 15.79mm for the 6K 6:5 (ANA) height of the Dragon sensor.

 

So you'd need a 36mm anamorphic lens on the Dragon to match the view of a 40mm anamorphic lens on a 4-perf 35mm camera.

 

The thing is that you could always cheat and use a spherical wide-angle lens when you needed to go much wider in view -- "Monuments Men" did that.  When shots get that wide in view and that short in focal length, the bokeh is harder to judge unless you are focused very close so that the background goes soft.


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#6 Alex Stone

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Posted 02 August 2016 - 02:19 AM

Thanks David. Interestingly, after creating this graphic someone else linked me to this thread in which you also come to the answer of x1.13! My exact calculations came closer to x1.125... but x1.11 to x1.13 is just splitting hairs and equates to less than a millimetres difference in focal length anyway.

 

The Hawk C-Series only consists of 40, 50, 60, 75 and 100mm; perhaps you were thinking of the V-Series?


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#7 David Mullen ASC

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Posted 02 August 2016 - 11:22 AM

I was thinking of the Panavision C-Series, sorry... you did say Hawk in the original post.

 

Not sure how I got 1.13X the first time I calculated it.  If you use the anamorphic camera aperture height, not the projector aperture height, of 18.59mm then you get a 1.17X figure.

 

Maybe I had a different figure before for the 6K 6:5 dimensions. Or maybe I trimmed the resulting 2.40 : 1 image on the sides down to 2.38 or something.

 

Oh, I see, looking at the thread before, I was comparing the Alexa sensor area to the Red Dragon sensor area, not comparing 4-perf 35mm to Red Dragon.

 

The Alexa sensor height is 17.82mm.  The 4-perf 35mm anamorphic projector gate height is 17.5mm. 

 

Comparing 17.82mm (Alexa) to 15.79mm (Red Dragon) you get 1.13X.


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#8 Alex Stone

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Posted 02 August 2016 - 12:03 PM

It's an interesting technical exercise (for my brain), though we've now decided to shoot Alexa XT anyway!


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