The Viltrox AF 28mm f/4.5 is an ultra-compact wide-angle prime lens from the Chinese manufacturer Viltrox. It was specifically designed for mirrorless system cameras with full-frame and APS-C sensors. Due to its extremely flat design, it is barely thicker than a body cap.
Construction and Optical Design
The physical dimensions of the Viltrox AF 28mm f/4.5 are the most striking features of this optical system. With a depth of only about 15.3 millimeters and a weight of just around 60 grams, it is the flattest and lightest lens in the manufacturer's portfolio.
Despite these minimal dimensions, the optical construction consists of six elements arranged in six groups. Among them are two aspherical lenses and two elements made of ED glass (Extra-low Dispersion) to minimize aberrations and chromatic aberrations.
Due to the extremely compact design, the engineers had to forgo some classic features. The lens has no filter thread, making it impossible to use conventional screw-in filters such as ND or polarizing filters without special adapter solutions. There is also no lens cap; instead, there is an integrated sliding shutter on the front. This slider serves as physical protection for the front lens and makes a separate lens cap unnecessary.
The housing is solidly built despite the low weight and features a sturdy metal bayonet, which also includes a USB-C interface for future firmware updates.
Fixed Aperture
A technical special feature of the Viltrox AF 28mm f/4.5 is the fixed, non-adjustable aperture of f/4.5. The lens has no mechanically adjustable aperture blades, so the aperture is rigidly set to this value. Neither on the lens itself nor via the camera menu can the aperture be adjusted. This limitation simplifies the construction but restricts creative control over depth of field and exposure management in difficult lighting conditions.
The rigid, octagonal aperture opening, however, has a striking optical side effect: In night shots or backlit situations, the lens tends to produce a very pronounced eight-point star effect on point light sources, which is appreciated by many photographers as a creative stylistic tool. The minimum focusing distance is 32 centimeters.
Autofocus
For automatic focusing, Viltrox relies on a modern linear drive of the Voice Coil Motor (VCM) type. This focus motor works quietly, quickly, and precisely in everyday photography.
Another unusual feature for an autofocus lens is the complete omission of a manual focus ring. This means that manual focusing is not possible with this lens; the photographer is entirely dependent on the camera's autofocus performance.
Mount Compatibility
Viltrox has released the lens for four different mirrorless camera systems. It is available for Sony E-mount, Nikon Z-mount, Fujifilm X-mount, and the L-mount system (including Panasonic Lumix, Leica, and Sigma). On APS-C cameras such as Fujifilm models or smaller Sony bodies, the angle of view corresponds to a focal length of approximately 42 mm due to the crop factor, which is close to a classic normal focal length.
Sample Images
The sample photos were taken with the Fujifilm X-T20. The images were edited in Adobe Lightroom.
