The Viltrox 15mm f/1.7 is an ultra-wide, rectilinear prime lens designed for APS-C cameras, specifically for Fujifilm X, Sony E, and Nikon Z mounts. It's part of Viltrox's "Air" series, known for being lightweight, compact, and affordable, while still offering good image quality and autofocus performance. 

Here's a more detailed look at its features:

Wide Angle:

The 15mm focal length provides an 84.9° field of view, which is equivalent to 22.5mm on a full-frame camera. 

Bright Aperture:

The f/1.7 maximum aperture allows for shooting in low light and creates a shallow depth of field for background blur. 

Autofocus:

It utilizes an STM stepping motor for fast, accurate, and quiet autofocus, including support for eye and face tracking. 

Optical Design:

The lens typically features 12 elements in 10 groups, including ED, HR, and aspherical elements to minimize aberrations and improve image quality. 

Lightweight and Compact:

The lens is designed to be very portable, making it suitable for travel and everyday use. 

Affordable Price:

It's positioned as a budget-friendly option compared to native lenses with similar specifications. 

Other Features:

It typically includes a 58mm filter thread, supports electronic aperture control, and has a USB-C port for firmware updates.