HD Pentax-DA Fish-eye 10-17mm F3.5-4.5

Vignetting

In simple terms, vignetting is the darkening of the corners of an image that occurs at wider apertures. Every lens, wide open, will exhibit some. Most of the time, 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. Advanced software also often incorporates lens profiles which can seamlessly correct vignetting. Last, it is always possible to purchase higher-quality lenses that will show milder vignetting.

A fast lens is somewhat more likely to show vignetting than a slow one, although this is not a hard rule. A full frame lens also benefits from a sweet spot on APS-C, but shows its flaws more visibly on full frame cameras. A zoom is more likely to show vignetting at its wider focal lengths.

This section presents how the HD DA 10-17mm performs in regards to vignetting.

Vignetting Test

The test was performed by pointing the lens at a blank wall. In-camera correction was de-activated; results with lens correction active will be significantly better. Resulting files were scaled down, converted to grayscale for improved visibility, then exported. The following settings were used:

The following chart summarizes the findings with the HD DA 10-17mm.

It is expected that vignetting will be stronger at the widest angle, where distortion is also more prominent. Such high values will be noticeable. However, given the extreme field curvature, viewers will be much more likely to notice the distortion than the vignetting. Moreover, it is very difficult to obtain a uniformly lit scene, so in most occurrences, vignetting will be hard to notice.

At 14mm, vignetting is still strong wide open, but becomes much more manageable at F5.6. At 17mm, vignetting is not absent but should not be a problem as it will be hard to notice in the field.

The next images show the vignetting at various apertures. Click on any thumbnail to compare the vignetting at the given focal length.

	10mm	14mm	17mm
F3.5
F4 or F4.5
F5.6
F8

Verdict

Vignetting is important at 10mm. Luckily the extreme field of view and distortion are likely to make it hard to notice. Wide open at 14mm, it is still present. Vignetting will be hard to notice at 14mm and apertures equal or smaller than F5.6, and in general at 17mm.