Pentax-D FA 100mm F2.8 Macro WR
Vignetting
Vignetting is a fact of life. In simple terms, it is the darkening of the corners of an image that occurs at wider apertures. Every lens, wide open, will exhibit some. Luckily, it need not be a problem for modern photographers. First, it is always possible to shoot at smaller apertures, mitigating the effect. Second, cameras released in the last few years often have built-in tools to remove vignetting in a way that's invisible to the user. Last, it is always possible to purchase higher-quality lenses that will show milder vignetting.
The D FA 100mm macro WR is, in theory, such a lens. Let's find out how it performed.
Vignetting Test
The test was performed by pointing the lens at a blank wall, taking advantage of the close focus capabilities of the lens. In order to avoid the bias of the in-camera corrections, we shot each image both in JPEG and in DNG RAW, then used Lightroom to develop the RAW files (using default settings to develop the files). JPEGs and RAWs were scaled down, converted to grayscale for improved visibility, then exported. The following settings were used:
|
|
|
f2.8 JPEG |
f2.8 RAW |
|
f4 JPEG |
f4 RAW |
|
f5.6 JPEG |
f5.6 RAW |
|
f8 JPEG |
f8 RAW |
Verdict
As can be expected, JPEG files with in-camera correction show no visible vignetting, which is more a testament to the quality of the JPEG engine than to the lens. RAW files show slight vignetting at f2.8, with a difference of about 0.4 EV between the corners and the center. It is still barely visible at f4 (about 0.3 EV), and disappears at smaller apertures. Being a full-frame lens, it is somewhat expected to get such good vignetting performance on APS-C. Vignetting will be almost unnoticeable in everyday shooting.
