When choosing the best video lens for the Sony FX30, you have several excellent options to consider, such as the Sony E 16-55mm f/2.8 G lens, the Sigma 18-50mm f/2.8 DC DN Contemporary Lens, and the Tamron 17-70mm f/2.8 lens.

The Sony E 16-55mm f/2.8 G lens is a high-quality, versatile lens that offers a wide-to-standard zoom range, making it perfect for various video shooting scenarios. The constant f/2.8 aperture ensures excellent low-light performance and beautiful bokeh. Additionally, the lens features linear response MF for precise manual focus control, which is essential for video work.

The Sigma 18-50mm f/2.8 DC DN Contemporary Lens is another strong contender, providing a slightly longer focal range than the Sony. It also boasts a constant f/2.8 aperture and delivers sharp, high-contrast images throughout the zoom range. The lens is compact and lightweight, making it ideal for handheld shooting and gimbal use.

Lastly, the Tamron 17-70mm f/2.8 lens offers the most versatile zoom range among the three, covering wide-angle to short telephoto focal lengths. Like the others, it has a constant f/2.8 aperture for consistent performance. The lens also features Tamron's VXD linear motor focusing mechanism for fast, quiet, and precise autofocus, which is crucial for video work.

Ultimately, all three lenses are excellent choices for the Sony FX30, and your decision should be based on your specific shooting needs and preferences.

Tamron 17-70mm f2.8 is a good choice.

I use Sirui Cinema lenses for my fx30, works great.

Sigma 18-50mm f/2.8 DC DN C.