Viltrox AF 28mm F4.5 XF Review – Casual Snappy Slim for Fujifilm X-mount

By Keith Wee on March 19, 2025

Introduction

It has been a while since I have done any Fujifilm X-mount equipment reviews, with my last being the Fujifilm X-S20 in May 2023, and boy, it does feel nice to get in touch again with a brand that marked the beginning of review writing for me.

This time around, the focus of the review will be the Viltrox AF 28mm ƒ4.5 for Fujifilm X-mount, a lens that was made available to Sony full frame last year and known for being the lens as thin as a lens cap with auto-focus capabilities.

Whle 'lens-cap' lenses have been available for Fujifilm X-mount for years, the Viltrox AF 28mm marks the 1st with auto-focus capabilties.

Being one of the smallest APS-C autofocus lenses on the market, the Viltrox AF 28mm ƒ4.5 weighs only approximately 60 g with a 15.25 mm thickness. Its compact size allows smaller cameras, such as the Fujifilm X-M5, X-E4, X-S20, etc-cetra, to be much more compact or even pocketable when attached.

*an NP-W126S battery weighs approximately 51 grams compared to this 60-gram lens.

Let us take a deeper look.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, Classic Chrome

Technicalities

APSC Fujifilm X-mount, with auto-focus
28mm at ƒ4.5 fixed aperture (42mm full-frame equivalent focal length)
Viewing angle of 52 degrees
6 elements in 6 groups, including 2 ED lenses, 2 Aspherical lenses, and front lens water-proof coating.
Minimum focusing distance of 0.34 meters
Quiet VCM (voice-coil motor) focusing motor, which we see more commonly in Canon lenses
Built-in USB-C port on the lens mount for firmware updates
Diameter X Length at ⌀60.3 x 15.25 mm, at approximately 60 grams.

Source: Viltrox

Holding it was a pleasant surprise for myself noticing how thin the lens is, especially knowing that it was originally designed for full-frame.

Handling, build and performance

Despite the Viltrox AF 28mm ƒ4.5 priced at a quarter of the Fujifilm XF 27mm ƒ2.8, it feels reasonably solid with a metal bayonet. The design of the lens is really straightforward, with only a switch for one to slide open the lens cap when using it and nothing else on the lens's exterior. There is no focusing ring for manual focusing, either.

There is hardly 'anything to handle' as the Viltrox AF 28mm ƒ4.5 comes only with a physical switch to open/close the lens cover. There is no focus ring, no other switches nor buttons.

The Viltrox AF 28mm ƒ4.5 uses a voice-coil motor (VCM) autofocus system that only holds the lens element magnetically when powered on, which means that one does hear a rattle if you shake the lens while it is powered off. With this design, the entire lens unit moves together during focusing, though one is not likely to notice it, given the simple optical design.

One of the sacrifices Viltrox had to make for the compact size was, of course, maximum aperture, and that is also why the Viltrox AF 28mm ƒ4.5 was designed with a constant ƒ4.5 aperture. Let me be clear that the aperture value is fixed, and you cannot make any adjustments to it.

The lens's minimum focusing distance is clearly marked at 0.34 meters on the front. The Viltrox AF 28mm ƒ4.5 does not have any threads or means for the user to mount a hood, UV or ND filter, meaning that one is strictly limited to adjusting shutter speed and ISO values for exposure when in use. A USB-C port for firmware updates is at the back of the lens, near the mount.

On the Fujifilm X-mount system, the effective focal length is approximately 42mm, an increasingly popular focal length that we see in the Ricoh GR IIIx, Leica Q3 43 and, of course, Fujifilm's own XF27mm ƒ2.8 lens which comes with more functionalities such as a variable aperture from ƒ2.8 to ƒ16 and a focusing ring for manual focusing.

Working with a fixed aperture and a very good amount of depth of field, I simply set the camera in P mode, especially given that the Viltrox AF 28mm ƒ4.5 was probably designed for the street photographer keen on candid snaps.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, Classic Chrome

Haivng auto-focus capabilities is a real convenience and a huge plus in this lens-cap design Viltrox AF 28mm ƒ4.5 lens.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, Classic Chrome

A plus I was looking forward to is improved optical performance in this lens on the Fujifilm system versus the Sony full-frame system, based on the fact that on APSC sensor cameras, one should expect reduced vignetting and probably sharper images across due to the corners of the image circle not being used.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, Classic Chrome

Autofocus was as expected of the Fujifilm X-T50 camera; it was snappy and mostly on point, though this was nothing to shout about from the rooftop. The focus was also silent in continuous autofocus, which is a plus.

One habit I have is to use the focusing ring to manually override autofocus when the system fails to grab focus and I was unable to do so with this lens.

Working with a decent amount of available light, the Viltrox AF 28mm ƒ4.5's output is quite pleasant colour and contrast-wise, with nothing much to pick at, especially at the USD99 price point of this lens.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, ACROS (further edited)

There is a small amount of chromatic aberration and minimal distortion, which can be easily corrected in post-processing.

However, one might need to note that once one hits either a low-light situation or a strong back-lit situation, the output quality drops significantly in contrast or noise.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, ACROS (further edited)

The lack of a hood also leads to easier flaring, but I will say that this was pretty much expected given the lens design is not primed towards optical excellence but towards a balance of minimal price, small size and decent performance.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, ACROS (further edited)

Conclusions

In all, I have to say that Viltrox provided an interesting offering here with the AF 28mm ƒ4.5, where it is really fun to work with snapshots in a well-lit situation but presents its own set of limitations. It will surely attract a fair share of niche users who appreciate its balance of price, size, auto-focus capability and useful focal length.

Viltrox AF 28mm ƒ4.5 on Fujifilm X-T50, Classic Chrome

For these type of lenses, my take is take it for a fun creative spin once a while with no expectations.

The Viltrox AF 28mm ƒ4.5 is a lens hard to find fault with, given how decently it performs for the size of a lens cap and, well, similar to the price of a Fujifilm NP-W235 battery. It is a fun, lightweight addition to anyone's photography bag, and in fact, I might even forget about it and one day be pleasantly surprised to find it snuck in a corner of my camera bag and use it again.

Thank you for reading.

Disclaimers:

All product photos and samples here were photographed by me. I believe any reviewer with pride should produce their own product photos.

2. All images were shot with a loaner set of the X-T50 and my personal set of the Viltrox AF 28mm ƒ4.5. I might purchase an X-mount camera again if I have more X-mount lenses to test.

3. The Viltrox AF 28mm ƒ4.5 was provided for the review, and I was allowed to keep it.

4. I write as a passion and a hobby, and I appreciate that photography brands are kind enough to respect and work with me.

5. The best way to support me is to share the review, or you can always help support me by contributing to my fees to WordPress for the domain using the 'Buy me a Coffee' button at the bottom of the page.