Pentax-FA 43mm F1.9 Limited (APS-C)
Vignetting
Vignetting refers to the darkening of the corners of an image. For this test, we took photos of an uniformly-lit sky with the FA 43mm f/1.9 and a Pentax K-5 IIs body (with its vignetting correction feature disabled). It can be observed that, for practical purposes, there is no vignetting at apertures of f/2.8 or smaller (corner pixel values at more that 95% of center). At f/1.9 and f/2.0, there is some vignetting, but it is not intrusive in real world usage. We can conclude that the FA 43mm f/1.9 behaves very well in regards to vignetting.
| F1.9 |  | F2 |  |
| F2.8 |  | F4 |  |
| F5.6 |  | F8 |  |
| F11 |  | F16 |  |
Verdict
Shortly told, vignetting is a non-issue with this lens on an APS-C body. Even the small amount of darkening wide-open is insignificant.
