Pentax DA* 60-250mm F4 Review

Aberrations

On this page, we will take a look at how well the Pentax DA* 60-250mm lens handles aberrations, such as the darkening of corners or fringing.

Vignetting

We evaluated this lens's vignetting by photographic a clear blue sky at three focal lengths and at all aperture settings.  The following figure summarizes the results for wider aperture settings, at 1-stop increments:

Vignetting is well controlled even at wider apertures. It is more pronounced at 250mm, which is to be expected. It becomes a non-issue at F5.6 is virtually indiscernible at F8.

Distortion

As can be seen from the images below, barrel distortion is very moderate at 60mm. Distortion is almost absent at longer focal lengths, although some pincushion can be perceived at 250mm.

Chromatic Aberration

Chromatic aberration is hard to find on most images produced by the 60-250mm. The worst we have observed can be found on this image, shot at 250mm and F5:

A crop of the image is necessary to see the effect at the back of the white shirt:

Chromatic aberrations can creep up under rare circumstances but are generally not a problem with the 60-250mm. Crops are necessary to observe the presence of aberrations.

Flare

Flare occurs when a light source is placed near the edge of the frame in a picture. Every lens will exhibit some flare but its impact on the image will vary from one type of lens to the next. While it can be used to create artistic effects, in general flare is not desirable and should be minimized.

Pentax uses their SMC (Super Protect Coating) to help reduce flare (among other benefits). The DA*60-250 also has a Super Protect Coating on the front element. This coating is designed to protect the lens from grease, dirt and water, but its presence will impact the flare resistance of the lens.

The following images were captured to evaluate the presence of flare with and without a hood. The light source was placed right inside the frame and just outside of it. Click on thumbnails for larger versions.

Light source inside the frame, no hood	Light source inside the frame, with hood
Light source outside the frame, no hood	Light source outside the frame, with hood

As can be seen from these pictures, flare is very well controlled with the lens. With the light source inside the frame of the image, a red-pink patch can be seen and is the only visible manifestation of flare (this patch is caused by internal reflections between two lens elements). Using the hood in this case will not affect the result, obviously. With the light source bordering on the outside of the frame, flare is not readily observable, no internal reflections are visible. However, some blooming is apparent, and is decreased by the use of the lens hood.

Verdict

Overall, the 60-250mm lens does an exceptional job of controlling all kinds of aberrations, which is impressive.  It's only noticeable flaw is the pincushion distortion that is exhibited at the long end.