Positives

• One of the largest aperture lens in the Pentax lineup and still one of the cheaper ones even though it has increased in price over the years.
• Versatile lens thanks to the aperture ring, full frame coverage, approximate short telephoto focal length, and wide aperture.
• A good overall size for any Pentax camera body.
• Provides the sweet spot effect on APS-C cameras.
• Is very sharp in the center of the frame around f5.6.
• Holds sharpness well at small apertures.

Negatives

• My copy isn't the easiest lens to achieve perfect focus with. I had to perform the chart test twice with this lens and only once with the others.
• Overall construction is just okay. Tolerances with the inner barrel are a bit wide, the materials used are not Limited quality, serial number is a sticker, and the manual focus ring is thin.
• Not the best lens at handling chromatic aberrations.
• Corner sharpness is lacking for a good part of the aperture range compared to the DA 40mm and Mamiya 55mm.

Compared to Other Pentax Lenses

The DA* 55mm f1.4 SDM competes with the FA 50mm as an equivalent lens for tight portraiture (meant to replace the 85 f1.4 of old for APS-C). While I don't own a DA* 55mm, in my opinion it has an optimal focal length and has been described by others to have better sharpness and bokeh. In an interesting turn of events, the new DA-L 35mm f2.4 is the true successor of the FA 50mm f1.4 in focal length and intended audience, but it falls short when comparing aperture versatility. If your intention is to have a normal focal length prime. The last two options I feel are in the same ball park are the DA 40mm f2.8 limited (small portable quality) and FA 43mm f1.9 Limited (aperture ring and extreme quality).