Pentax SMC DA 55-300mm f/4-5.8 ED - Review / Test Report - Analysis
Lens Reviews - Pentax

Distortion

The Pentax lens exhibits negligible distortion at 55m. In the 100-300mm range you can expect a medium degree of pincushion distortion which may be visible at times in field conditions.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
55mm 100mm 200mm 300mm

Vignetting

Typical for most lenses with an APS-C format coverage the Pentax lens shows stronger vignetting at max. apertures (~0.8EV). The problem is largely reduced and no longer field relevant when closing the aperture by 1 f-stop.

MTF (resolution)

The Pentax 55-300mm f/4-5.8 ED is capable of producing quite respectable resolution figures throughout the focal length range. The center performance is generally on very good level with a rather typical quality penalty towards the long end of the zoom range. The border performance is a bit soft at max. aperture but the quality can be boosted when stopping down a little. The contrast in field images is pretty snappy - surely a positive effect from the ED element(s).

The tested sample showed an optical problem (centering) at 55mm which may have polluted the figures somewhat at this setting.

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations (CAs)

Lateral CAs (color shadows at harsh contrast transitions) are well controlled (< 1px) between 55mm and 200mm. At 300mm CAs may be visible in critical situations though with a peak width of around 1.5px at the image borders.




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