HD Pentax-DA 16-85mm F3.5-5.6

Sharpness

We start this section out with a sample photo just to illustrate the impressive center sharpness and level of detail rendered by this lens. The sample also provides a preview of bokeh which we will discuss in more detail later on.

Sharpness & BokehSharpness sample: Wide-open at 85mm | Click image for an unedited full-size crop (JPEG)

This lens is sharp in the center even when wide open. Sharpness improves further when the lens is stopped down (see the star charts below) and continues to be good until diffraction sets in at F11 or F13, depending on focal length.

The edge sharpness is comparable to the center except at 16mm, where there is a slight softness until the lens is stopped down by one stop or more.

We would expect the corners to be visibly softer particularly at the wide end, and the corners are softer, but not to a degree that one needs to worry about. At small apertures (from F11) at the wide end diffraction takes more of a toll in the corners than at the edges and center. At longer focal lengths this difference between corner and center diminishes. 

All in all this lens performs better and more uniformly at the edges and corners than the Pentax 18-135mm, which suffered from poor corner sharpness. The 16-85mm's performance is respectable considering the short focal length (16mm) at the wide end.  Subjectively, the images produced by this lens appeared just as sharp as what we've seen from premium zooms such as the DA* 16-50mm.  This lens is thus worth considering in lieu of the former if you do not need the faster aperture and are looking for something more compact.

The graph above illustartes the apertures where the lens resolution peaks. Refer to the star charts below for details.

Star Charts

We used our star chart to gauge resolution and contrast over the range of apertures. The charts for a given focal length are directly comparable (center - edge - corner). When you compare the results from one focal length to the next (16mm corner - 35mm corner for example) you should ignore the slight difference in the magnification of the center target and instead look at how far the blurred area extends.

The thumbnails represent full-resolution crops. You can also click on a thumbnail in each column to browse larger full-resolution crops for that column on the light box.

16 mm
 
Center
Edge
Corner
F3.5
F4
F4.5
F5.6
F6.7
F8
F9.5
F11
F13
F16

35 mm
 
Center
Edge
Corner
F4.5
F5.6
F6.7
F8
F9.5
F11
F13
F16

50 mm
 
Center
Edge
Corner
F4.5
F5.6
F6.7
F8
F9.5
F11
F13
F16

85 mm
 
Center
Edge
Corner
F5.6
F6.7
F8
F9.5
F11
F13
F16

Our findings are shown in the table below.

Verdict

We can conclude the following about the apertures where the lens is at its best:

Center
Corner
Best aperture
Close second
Best aperture
Close second
16mm F6.7 F4.5, F5.6, F8 F8, F9.5, F11 F6.7
35mm F6.7, F8 F5.6, F9.5, F11 F6.7, F8 F5.6, F9.5, F11
50mm F6.7, F8 F5.6, F9.5, F11 F8 F6.7, F9.5, F11
85mm F6.7, F8 F5.6, F9.5 F8, F9.5 F5.6, F6.7

This lens performs well across all the focal lengths. While there is some slight softness in the corners wide open at 16mm, it is less prominent than we would have expected from this wide of a focal length. At the other end of the aperture range the inevitable diffraction starts taking its toll at F11 to F16 depending on the focal length.

It is no small feat to achieve this kind of perfomance in a 5x zoom starting at a wide 16mm.  We can therefore conclude that the 16-85mm is among the sharpest choices among standard zooms for Pentax, even alongside the DA* 16-50mm F2.8, and it thus leaps well ahead of the kit lenses in this regard.  While the 16-85mm's maximum aperture is not a fast lens compared to alternatives such as the Sigma 17-70mm F2.8-4, it is wonderful to see that it performs so well at nearly all available aperture settings. Our findings with respect to sharpness were confirmed with a second copy of the lens.

For a direct sharpness comparison with the Pentax 18-135mm WR, DA* 16-50mm, and other lenses, visit forum member/staff writer Heie's user review.


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