Viltrox AF 40mm 2.5

The Viltrox AF 40mm f/2.5 Z is a bit of an oddity as a prime lens. While it performs quite well in most aspects, it doesn't stand out overall. The lens is pretty sharp in the broader image center straight from f/2.5, whereas the outer image field is not overly inspiring at this setting. This improves when stopping down, but even at its optimal setting around f/5.6 the border/corner quality doesn't go through the roof - although a good to very good performance is far from being bad either here. Lateral CAs are well controlled, less so axial CAs. Viltrox doesn't offer profile correction for image distortions. This wasn't really an issue with most of their lenses because they were well-corrected. However, the 40mm f/2.5 Z produces medium pincushion distortion, which can be noticeable in some scenes at least. The vignetting characteristic is decent, especially when auto-corrected. Sun stars are very nicely rendered, and the bokeh is pretty good, too. On the downside, RSA/focus shift may have a negative impact in close focus scenarios. The build quality is pretty good, especially considering the very low price point of just $150 USD. The small, and very lightweight lens body is made of decent-quality plastics based on a metal mount. The focus ring operates smoothly, and the AF is fast enough. Overall, the Viltrox AF 40mm f/2.5 Z seems to be stuck between a rock and a hard place. It's not a pancake lens to benefit from a cuteness factor, and it's not fast enough to compete with the nifty fifty. So this just leaves the 40mm focal length and ultra-low pricing as differentiators.