Pentax K-01 Optics

40mm Prime
Excellent performance with the Pentax 40mm f/2.8 XS kit lens.

The Pentax K-01 is usually bundled with the new smc PENTAX-DA 40mm f/2.8 XS "pancake" prime lens, providing a 60mm equivalent focal length. Sharpness and contrast are very good across the frame stopped-down to f/8, with low levels of coma distortion and chromatic aberration in the corners (though the K-01 does suppress lateral chromatic aberration in its JPEGs), and little sign of flare. Excellent results here.

Macro
Larger-than-average macro area with the 40mm lens, with slightly soft detail. Flash has trouble up close.

With the Pentax 40mm f/2.8 XS pancake lens, the K-01 captured a much larger-than-average macro area, measuring 6.89 x 4.56 inches (175 x 116 millimeters). This is definitely not a macro lens. Detail was good but a little soft in the center of the frame, and a little softer in the extreme corners. (Most lenses have some softening in the corners at macro distances.) The Pentax K-01's built-in flash didn't throttle down well in auto mode overexposing the image by quite a bit, though some negative flash exposure compensation may have helped here.

Geometric Distortion
Fairly low distortion with the 40mm lens.

The Pentax 40mm lens produced about 0.25 percent barrel distortion which is fairly low, though keep in mind that this is slightly telephoto prime lens. Geometric Distortion is the tendency for the lens to bend straight lines outward (like a barrel -- usually at wide-angle) or inward (like a pincushion -- usually at telephoto).

Distortion Correction
The Pentax K-01 offers optional Distortion Correction when using DA, DA L, and DFA lenses, as well as several of the company's FA Limited lenses.

The Pentax K-01 does not apply any geometric distortion correction to JPEGs by default. There is however a menu option to turn Distortion Correction on. RAW files are not corrected, but are tagged to have the same correction applied when using a RAW converter that supports the embedded parameters. The crop above shows a JPEG taken with the 40mm kit lens with Distortion Correction enabled. The 0.25% barrel distortion in the uncorrected file has been eliminated, with a slight over-correction to about 0.05% complex pincushion distortion.

Chromatic Aberration and Corner Sharpness
Low levels of lateral chromatic aberration from the 40mm lens, though the K-01 suppresses it in JPEGs. Slightly soft corners wide-open, but good corner sharpness stopped-down.

Chromatic Aberration. Chromatic aberration is moderately low and dull in the corners of the Pentax 40mm lens wide-open, but the K-01 suppresses lateral chromatic aberration by default (see below). There's some moderate longitudinal chromatic aberration in the center at f/2.8, but that will likely vary with focus. At f/8, chromatic aberration is much lower and hardly noticeable. (This distortion is visible as a slight colored fringe around the objects at the edges of the field of view on the resolution target.)

Corner Sharpness. The Pentax 40mm lens produced slightly soft corners at the top of the frame at maximum aperture, but bottom corners were sharper. Softness extended pretty far into the frame, though the center was fairly sharp. Corner sharpness was pretty good when stopped-down to f/8. Some vignetting was noticeable at f/2.8 as well, but negligible at f/8.

Chromatic Aberration Reduction
The Pentax K-01 offers optional lateral chromatic aberration reduction for the same lenses that are supported for distortion correction.

As illustrated in the crops above, the Pentax K-01 removed much of color fringing from the 40mm kit lens with Lateral Chromatic Aberration Adjustment enabled (default), though it still leaves some minor chromatic aberration behind, especially along diagonal edges. Note that longitudinal chromatic aberration does not appear to be suppressed (from the center crop at f/2.8).

Overall, very good performance from a pancake lens. Only macro performance is somewhat disappointing, but that's not a surprise given how compact the lens is.

Coverage
Very good accuracy from the LCD.

The Pentax K-01's LCD showed about 101 percent coverage with our Sigma 70mm f/2.8 prime lens. This is very good performance compared to most SLRs, but we like to see 100% coverage from an LCD.