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Anamorphic stretch/crop math


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#1 Steven C. Boone

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Posted 27 November 2016 - 06:15 PM

Hello,

 

I'm shooting a microbudget short with a couple of old 2X anamorphic lenses. I would prefer to use the crop sensor (APS-C) Nikons and Sonys at my disposal but recognize that the 2X squeeze would un-squeeze at a much wider than standard 2.35:1 ratio.

 

What I'd like to know: Cropping the sides to 2.35:1 in post from the un-squeezed footage, exactly how much resolution would I lose? And is there a resolution figure (i.e. 1080p, 720p) one could draw from the resulting crop?


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#2 David Hessel

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Posted 27 November 2016 - 07:09 PM

The crop horizontally we would be aprox 1.5 assuming a 16:9 source. Basically you need to crop away about 1/3 of the horizontal resolution if shooting with a 16:9 camera and a 2x anamorphic at 2.35:1.
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#3 David Mullen ASC

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Posted 27 November 2016 - 08:49 PM

Let's say that you did an HD recording, standard 1920 x 1080 pixels (1080P), which is a 1.78 : 1 (16x9) aspect ratio... but you had a 2X anamorphic lens on the camera.

 

You can figure it out a couple of ways, the math is easy, but if your image has a 2X horizontal squeeze to it and you want the final unsqueezed image to be 2.40 : 1, then that means the unsqueezed image area is 1.20 : 1.  So ignoring the squeeze for a moment, you can think of this as only using a 1.20 : 1 area of your 1.78 : 1 recording.

 

Another way to think of it is if the vertical remains 1080 pixels, then the width used to get 1.20 : 1 is 1080 x 1.2 = 1296.  So this means you'd be cropping 1920 pixels to 1296 pixels.

 

Of course, at some point, 1296 x 1080 pixels has to be converted to a standard format and unsqueezed -- for example, maybe a 1920 x 1080 HD recording with a 2.40 letterbox.  Or maybe a scope 2K DCP, which is 2048 x 858 pixels.


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#4 Steven C. Boone

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Posted Yesterday, 02:54 PM

Let's say that you did an HD recording, standard 1920 x 1080 pixels (1080P), which is a 1.78 : 1 (16x9) aspect ratio... but you had a 2X anamorphic lens on the camera.

 

You can figure it out a couple of ways, the math is easy, but if your image has a 2X horizontal squeeze to it and you want the final unsqueezed image to be 2.40 : 1, then that means the unsqueezed image area is 1.20 : 1.  So ignoring the squeeze for a moment, you can think of this as only using a 1.20 : 1 area of your 1.78 : 1 recording.

 

Another way to think of it is if the vertical remains 1080 pixels, then the width used to get 1.20 : 1 is 1080 x 1.2 = 1296.  So this means you'd be cropping 1920 pixels to 1296 pixels.

 

Of course, at some point, 1296 x 1080 pixels has to be converted to a standard format and unsqueezed -- for example, maybe a 1920 x 1080 HD recording with a 2.40 letterbox.  Or maybe a scope 2K DCP, which is 2048 x 858 pixels.

 

Thanks to both of you for the very helpful answers.

 

It sounds like I'd end up with an image that would still hold up on large displays and moderately sized cinema screens. As enthusiastic as I am about using modest equipment to deliver a cinematic look, I still want to leave my director with as many options as possible in the finish.


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#5 Stuart Brereton

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Posted Yesterday, 03:50 PM

Although you are going to lose some resolution by cropping left and right , it's not actually that much more than you would lose by shooting spherically, and then letterboxing to 2.40:1

 

Spherical Crop. 1920 x 800 = 1.53 MP

 

Anamorphic Crop 1296 x 1080 = 1.39 MP


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