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Anamorphic lenses and rolling shutter effect


stefanmedia
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Do anamorphic lenses (on CMOS cameras) reduce or worsen the rolling shutter effect?

 

I'm thinking that anamorphic lenses should reduce the effect. Because the lens compresses the horizontal dimension, objects appear thinner as they are recorded so there is less horizontal movement (as objects move horizontally) during the rolling shutter's operation. This would imply that as a vertical object passes by the lens (quickly), the rolling shutter effect isn't too pronounced when you stretch the footage to a widescreen aspect ratio.

 

But on a forum post (on this site), someone wrote, "rolling shutter being exaggerated by the horizontal stretch." So maybe my thinking about this is missing something?

 

Has anyone done a test? I searched online for "anamorphic" and "rolling shutter effect" but I don't see any (immediate) answers.

 

Thanks in advance for any insights people can give.

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Imagine a perfect straight vertical line with a white background. Let's say that at a given rotation of the camera the line will have a certain amount of horizontal displacement, Dx (the horizontal distance between the top and the bottom). Since this deformation comes from the sensor and the line is one dimensional, the image and therfore the displacement Dx will be exactly the same with or without the anamorphic lens.

Once you unstretch the anamorphic (2x stretch) one you will get 2*Dx. The effects of rollinshutter in this case would be 2 times worse.

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