This limited-edition Pentax fixed lens that came out in 2009 is a pancake lens with a focal equivalent of 24mm on a full-frame camera… so it isn’t a very wide-angle lens. Compact, it measures 39.5mm long and weighs in at 212g. It will certainly adapt very well to the upcoming Pentax K01 that we hope to be able to test quickly.

The optical formula of this 15mm lens integrates a low-dispersion (ED) glass element to limit chromatic aberrations, and an aspherical element (AL) to correct distortion.

Note that this limited edition has benefited from particular attention to quality and finish. Although it’s difficult to verify the ways in which its manufacture is different, the number of lenses produced per day has been deliberately limited to better control per-unit quality.

Measurements

Pentax SMC DA 15mm F4 ED AL Limited mounted on a Pentax K5

The strong points of the Pentax smc DA 15mm F4 ED AL Limited:

  • Very well-controlled distortion for this type of lens.
  • At full aperture, vignetting darkens only the corners.

The questionable points of the Pentax SMC DA 15mm F4 ED AL Limited:

  • Not a bright lens.
  • Despite the ED glass element, chromatic aberrations are visible.
  • The resolution is rather disappointing.

Comparison

Pentax SMC DA 15mm F4 ED AL Limited mounted on a Pentax K5 vs Nikon AF Nikkor 20mm f/2.8D mounted on a Nikon D7000

The Pentax 15mm achieves a DxOMark score that is four points lower than that of the Nikon 20mm. What makes this comparison even more pertinent is that both cameras use the same Sony sensor.

The advantages of the Pentax SMC DA 15mm F4 ED AL Limited:

  • Better correction of distortion.
  • Better correction of chromatic aberrations.

The advantages of the Nikon AF Nikkor 20mm f/2.8D:

  • Better sharpness.
  • A brighter lens.
  • Better correction of vignetting.

For more information, see the complete DxOMark results for the Nikon AF Nikkor 20mm f/2.8D.

Pentax SMC DA 15mm F4 ED AL Limited vs Pentax SMC PENTAX DA 14mm F2.8

Pentax offers two choices at nearly the same price, this 15mm f/4 lens and a 14mm f/2.8 lens. Photographers who prefer compactness will want to seriously consider the 15mm f/4, even though the 14mm f/2.8 is slightly brighter.

In terms of image quality, the two lenses are fairly close. Although the 15mm f/4 better controls both distortion and chromatic aberrations, its overall results are hampered by its weak resolution and its serious lack of uniformity in the field.

For more information, see the complete DxOMark results for the Pentax SMC PENTAX DA 14mm F2.8.

Conclusion

The SMC DA 15mm F4 ED AL Limited is an interesting lens that we wish were brighter. While its control of distortion is remarkable, its resolution is a bit weak, which is a shame, since it means that photographers will not be able to take full advantage of the Pentax K5’s 16Mpix sensor. In short, this lens could be improved to better appeal to those looking for a compact wide-angle.