Even after you buy a new and tested lens, still, there are improvements that can be made. Using the Sigma docking system, Videographer Armando Ferreira gives the low-down on how to apply some of those improvements using firmware updates.
If you own a Tamron or Sigma lens, you're probably aware that each company sells their own USB docking station so that you can modify their focus settings or update their firmware. The new releases from these third-party lens makers, such as Sigma's Art range, all contain microprocessors for this very purpose. Sony users can just update their lenses firmware by connecting the camera to a computer with the desired lens attached. Unfortunately, users of older Canon and Nikon bodies need to send their lenses to their respective manufacturers to get theirs updated, while those with newer bodies can do it through the camera.
In this succinct explanation, Ferreira goes through the reasons why you might want to consider updating the firmware on your lens. For his example, he uses Sigma's USB docking station to update his 18-35mm Sigma Art lens. As he points out, it's a very simple process that can really improve the performance of your lens, and I have to agree with him on his opinion of this specific lens. Even though it's especially designed for cropped sensor, or "enthusiast" DSLRs, it's one of the sharpest lenses that I've ever uses, buttery focus ring, the fastest zoom on the market at f/1.8, and has lovely bokeh wide open.