HD vs. SMC Pentax-DA 18-50mm F4-5.6

Chromatic Aberration

Chromatic aberration occurs when colors do not all have the same focal point. It results in a slight shift between the red, green and blue channels, visible mainly at the boundary between contrasted areas (black and white, for instance). It occurs to some extent with all lenses, and can be controlled by the use of achromatic elements. It can also be corrected fairly easily in post-processing. Modern cameras have an automatic correction mode that can effectively remove any pronounced chromatic aberrations.

Chromatic Aberration Test

For this test we used a well-lit, sharp transition from dark to bright, in order to demonstrate any chromatic aberration present in the image. The K-3's automatic CA correction was disabled. Various apertures were used. The lenses were set at 18mm since wider focal length usually show more CA. The image is tilted at approximately 45° of the focal plane of the camera.

We then looked at three parts of the image: the focus point, the top, and the bottom (beyond and before the focus point). You can click on the images to see larger views, and navigate each aperture image set by using the left-right arrows.

Focus Point

18-55mm DA L 18-50mm HD 18-50mm
F3.5 18-55 f3.5 Center
F4 18-55 f4 Center DAL f4 Center HD f4 Center
F5.6 18-55 f5.6 Center DAL f5.6 Center HD f5.6 Center
F8 18-55 f8 Center DAL f8 Center HD f8 Center
F11 18-55 f11 Center DAL f11 Center HD f11 Center

Performance in the central, in-focus area are above our expectations, showing no discernible chromatic aberrations for either of the three lenses.


18-55mm DA L 18-50mm HD 18-50mm
F3.5 18-55 f3.5 top
F4 18-55 f4 top DAL f4 top HD f4 top
F5.6 18-55 f5.6 top DAL f5.6 top HD f5.6 top
F8 18-55 f8 Top DAL f8 Top HD f8 Top
F11 18-55 f11 Top DAL f11 Top HD f11 Top

The top shows a strong color shift visible as a green on the black-to-white transition. None of the lenses tested differentiated from the others, though the new 18-50mm design might have a small edge. The HD coatings did nothing to improve CA control.


18-55mm DA L 18-50mm HD 18-50mm
F3.5 18-55 f3.5 bottom
F4 18-55 f4 bottom DAL f4 bottom HD f4 bottom
F5.6 18-55 f5.6 bottom DAL f5.6 bottom HD f5.6 bottom
F8 18-55 f8 bottom DAL f8 bottom HD f8 bottom
F11 18-55 f11 bottom DAL f11 bottom HD f11 bottom

Aberrations show themselves mainly as purple fringing in the bottom of the frame. The absence of such a behavior in the top part suggests that, in this case, PF is caused by the lenses. Again none pulls ahead; the three lenses show fringing at all apertures.


The lenses perform very well for in-focus subjects, showing no visible chromatic aberration. Things are different in the out-of-focus areas, however, with all three lenses exhibiting both chromatic aberration and purple fringing. All three versions showed about the same amount of fringing, which is moderate. It could still be visible in highly contrasted scenes. Luckily third-party softwares can remove many chromatic aberration effects, and in-camera corrections can also fix CA for JPEG files. This correction slows down the camera's operation, but we recommend using it if you do not wish to spend time post-processing your images.

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