But there are also image artifacts caused by rolling shutter, anamorphic lens distortion, focus changes on anamorphic lenses, or even footage where the action is happening in a mirror or on the other side of a glass window.
In every case, Yannix has developed a VFX pipeline that can model and reconstruct what is happening when the live action footage is captured so that the CG elements match as tightly as is possible.
While VFX is done on digital images made up of rows of pixels, the images are captured from the real world where rays of light bounce off of objects, pass through a lens and are focused onto an image capture plane (previously film, but nowadays a digital image sensor such as a CCD or CMOS).
In order to understand image artifacts such as “lens distortion” or “rolling shutter”, it helps to think about what is happening at the moment of the image capture.
“Rolling shutter” is a method of image capture where the image is scanned (normally top to bottom) such that different rows of pixels in the resulting digital image are captured at different times.
This is in contrast to “global shutter” where all pixels of the image are captured at the same instant in time. Rolling shutter may be either mechanical or digital, but the effect on the images is the same. When creating VFX for footage captured with a rolling shutter, any camera motion or objects moving in the plate will result in skewing or stretching which can have a significant impact on the VFX pipeline.