Image Quality

The HD Pentax-D FA* 50mm F1.4 SDM AW offers excellent resolution at all apertures and focal lengths, and is nicely flare-resistant. It also creates attractive-looking sunstars, and depending on conditions, beautiful bokeh. The only serious weakness is green / magenta fringing in front and behind of the point of focus, which - depending on subject choice shooting conditions - can get seriously distracting.

Key takeaways:

  • Excellent sharpness at all apertures
  • Excellent consistency across the imaging area
  • Practically no distortion
  • Lovely bokeh (most of the time)
  • Longitudinal chromatic aberration (LoCA) is fairly severe and can be distracting

Clearly a major draw of any lens of this kind is its wide maximum aperture, so it’s good to discover that sharpness in the center of the frame at F1.4 is excellent. Central sharpness continues to improve as you stop down, until you hit F2.8 where the lens achieves its best result. While consistency across the frame at wide apertures is excellent, corner sharpness does improve considerably as you stop down, appearing very sharp at F2.8 and achieving its best result by F4-5.6.

At these apertures, resolution at infinity is absolutely excellent. The Pentax lens even holds its own against the Canon RF 50mm F1.2L, another high-performing, modern 50mm lens, and one that costs considerably more. Explore the scene and you'll see the results are very impressive.

Ricoh claims that this lens has zero curvilinear distortion, and that appears to be true.

ISO 100 | 1/160 sec | F8

Mild vignetting is more obvious, but this is easily dealt with either in camera or later when processing images. Beyond F2.8 it's effectively gone.

Some green and magenta lateral chromatic aberration can be seen towards the peripheries of the frame when there are subjects with defined edges or high-contrast details, but this is minor and can be quite easily corrected in post, if you're shooting Raw.

What’s not so easy to deal with, however, is longitudinal CA, which is where this lens is weakest. Many images captured at the widest apertures display fringing around defined edges, although this can also be seen in images where the is a more gradual transition between focused and defocused areas. Unlike lateral CA, longitudinal CA is virtually impossible to correct.

Bokeh is typically nice and smooth in the centre of the frame, and very natural in appearance when the points of light are completely defocused. There’s just the faintest, very occasional, onion-ring pattern if you’re really looking for it, but overall, assuming your background consists of relatively low-contrast elements, you can expect really beautiful bokeh from the Pentax 50mm F1.4 at wide apertures - one of the benefits of a relatively simply aspherical design.

Moderate 'cats-eye' bokeh is visible at the edges at F1.4, but out of focus highlights are almost perfectly circular from F1.8 to F2.8.

Open this image at full size and look at the transition are between areas in front and behind of the plane of focus, just in front of our subject's nose. The green fringing behind the focus point - and the magenta fringing in front of it - is longitudinal chromatic aberration, or LoCA.

ISO 100 | 1/2500 sec | F1.8
Picture by Wenmei Hill.

Flare is well-controlled but fairly easy to introduce when the sun is low in the sky, sometimes appearing as a faint handful of blotches that can be easily cloned out but occasionally taking on a more prominent shape that might not always be desired but could still be used creatively.