HD Pentax-DA 40mm F2.8 Limited

Sharpness

The DA 40mm Limited delivers sharpness straight from wide open, both in the center and in the corner, with the latter surprisingly close to the former. One or two stops from wide open showed biting sharpness edge-to-edge, provoking strong moire in the K-5 IIs at normal testing distances.

In our real-world testing, the DA 40mm Limited always produced sharpness where it was needed. The scene below is much farther than typical lens tests, showing a worst-case scenario. The crops below are from the center and far edge of the following scene:

K-5 IIs, 1/8s, f/5.6, ISO 200

Center
Left Edge
F2.8
F4
F5.6
F8
F11
F16
F22

Compared to the DA* 16-50mm

The crops below show a typical star chart at various apertures compared to the elite DA* 16-50mm F2.8 lens zoomed to about 40mm, taken with a K-5 at ISO 200 under studio lighting.

Center Sharpness

In the center of the frame, both lenses are acceptably sharp starting wide open, with a slight edge to the Limited. Just one stop down and both lenses are excellent, with peak sharpness around F5.6. Starting at F16, diffraction starts to soften across the whole image.

Center Crops, Unsharpened (click for full size crops)
HD Pentax-DA 40mm F2.8 Limited
SMC Pentax-DA* 16-50mm F2.8
F2.8
F4
F5.6
F8
F11
F16
F22

Corner Sharpness

While the centers were closely matched, the DA 40mm Limited has markedly sharper corners at most apertures. While this isn't a huge surprise, since the simple fixed-focus design of the DA 40mm Limited should have an advantage, but at less than half the price and one-sixth the weight, the DA 40mm Limited beats the DA* decidedly.

One of the most noticeable differences is at F2.8 — but not just in sharpness. The DA 40mm Limited shows significantly less chromatic aberration, lending to the excellent results at all apertures. The DA* doesn't catch up in the corners until F5.6, which in its defense starts to get excellent.

Corner Crops, Unsharpened
HD Pentax-DA 40mm F2.8 Limited
SMC Pentax-DA* 16-50mm F2.8
F2.8
F4
F5.6
F8
F11
F16
F22

Verdict

Our real-world shooting shows the DA 40mm Limited to have good to excellent sharpness throughout its aperture range, at least until diffraction starts. Edge sharpness is remarkably close to the center. The perceived sharpness is aided by a low amount of chromatic aberrations.

Compared to the pro-grade DA* 16-50, the smaller and less expensive DA 40mm Limited is as sharp or sharper across the image plane at all apertures. The star charts show excellent sharpness in the extreme corners, only slightly softer wide open and suprisingly consistent stopped down.


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