Hi, there are several options for video production and it depends on your desired use-ability and end-results. There are several servo-zoom lens options (both APS-C and Full-Frame format) that can be used with your a6400. Look for a lens model starting with SELP to ensure that the lens has a Powered Zoom. These will also usually have a rocker switch on the lens barrel for consistent zooming speed. Truth is, you could use any of the E-mount lenses to produce fine looking video, primes can give you very shallow depth of field and greater light gathering ability, and zooms give you that flexibility if you're unable to move around much. Other considerations could be: weight, minimum focusing distance and AF motor noise (if you're capturing audio on-camera).
