Anytime you watch a rocket launch on the internet from the comfort of your home, you have incredibly precise imaging equipment to thank for the clear picture and butter-smooth tracking.
A camera operator with your typical handheld camera wouldn't be able to capture such impressive footage. It would be extremely challenging to keep the fast-moving rocket in the frame. Moreover, consumer-grade cameras don't come with the zooming capabilities required to capture footage of sky-borne rockets this clearly.
Instead, rocket manufacturers rely on specialized long-range tracking cameras mounted all around the rocket's launch pad. Most of these cameras track the rocket automatically to ensure smooth tracking. They also have the zooming capabilities required for obtaining an ultra-clear picture of the rocket despite being so high in the sky.
While these cameras indubitably provide incredible footage for our viewing pleasure, they also allow rocket engineers to study a rocket's performance. From this data, they can improve the rocket's design and make space travel safer.