In VFX video composition is rarely done in actual video formats like MOVs or AVIs because when using these formats it one of the frames corrupts or breaks the whole video is rendered useless and must be re-done not to mention the lengthy time it takes to render with this format in the first place. So VFX compositing is done as still frames/renders, then written together as a video. This way if a frame corrupts it is easy to find a re-render without affecting any of the other frames.
Common file formats
Openexr (.EXR)
The .EXR format is an incredibly powerful format that has both a high dynamic-range (HDR) and is very space efficient. .EXR can hold 1023 channels and also supports 16 bit and 32 bit depths. It is the most common render format due to the space effective HDR.
Targa (.TGA)
Same as an .EXR however doesn’t have a HDR. It is used in place of .EXR for normal mapping as .TGA can support 24 or 32bit and RGB/RGBA.
Tagged image file format (TIFF)
A method of lossless compression very space consuming.
Portable network graphics (PNG)
Very good at handling and storing transparency so it is commonly used for alpha maps.
The .JPEG format is very very rarely used due to its easy corruption / datamoshing and compression method that destroys a lot of data however it is very fast and simple with the compression.
Blobstersincorporated 