HD Pentax-DA 55-300mm F4.5-6.3 PLM WR RE
Distortions are unfortunately a fact of life when shooting with zoom lenses. Typically, a zoom will present barrel distortion at its widest end, then flip to pincushion distortion as it nears full telephoto. However, telephoto zooms are usually less susceptible to this issue than those that try to cover a wide-to-telephoto perspective, so we were hopeful that the HD Pentax DA 55-300mm F4.5–6.3 ED PLM WR RE would come through relatively unscathed.
Barrel distortion (left), no distortion (center), pincushion distortion (right)
The way we evaluated distortion is pretty straightforward: We took a picture of a grid printed on a piece of paper, and looked to see if and how its lines curved.
Most Pentax cameras include built-in distortion correction, which uses known distortion values to correct JPEGs and make bent lines straight. We shot this test with distortion correction turned on, but also shot in RAW + JPEG. The results below are from the RAW files.
Distortion Test Results
The 55-300mm PLM exhibits slight barrel distortion at 55mm. It's nothing to worry about for most purposes—even architectural shots won't look grossly distorted without correction. This evens out around 80mm, then flips to pincushion at 120mm. From this point, the pincushion distortion continues to worsen, but even at 300mm it isn't serious.
The DA 55-300mm ED PLM WR RE is quite well corrected for distortion, and what little curvature made it through the design process can be easily corrected for in-camera or in your editing suite of choice. We see little cause for concern here.