Pentax-DA 18-55mm F3.5-5.6 WR Review

Sharpness

To test for center and corner sharpness of the 18-55mm WR, we used the following chart:

Shown below are the center and corner crops of the test images, taken at a variety of focal lengths and apertures (click on thumbnail for actual size):

18mm

18mm Center Corner
f/3.5
f/4
f/5.6
f/8
f/11
f/16
f/22

In the 18mm focal length, the DA 18-55mm WR is relatively sharp in the center, peaking at f/5.6-f/8 and starting to diminish at f/16 due to the effects of diffraction. For the corners, they are quite soft from wide open until f/8-f/11, when it becomes barely acceptable, before diffraction again softens the image at f/16. This lack of sharpness at the corners is most likely due to the significant distortion and field curvature of this lens at its widest focal length.

24mm 

24mm Center Corner
f/4
f/5.6
f/8
f/11
f/16
f/22
f/29

When used at 24mm, the sharpness in the center is very decent from wide open until f/22. Diffraction seems to affect the image slightly less at this focal length. While the corners are noticeably softer than the centers, they are much better than at 18mm and peak in sharpness at f/8 and f/11, with f5.6 being not too far behind. At f/29mm, the effects of diffraction become very apparent so we suggest avoiding this aperture setting.

35mm

35mm Center Corner
f/4.5
f/5.6
f/8
f/11
f/16
f/22
f/32

At 35mm, the DA 18-55mm WR behaves slightly better than at 24mm. Center sharpness is very satisfactory until f/22, while the corners lag a bit behind, but are still very acceptable. At f/32, the softness is so prevalent that the image is hardly usable.

55mm

55mm Center Corner
f/5.6
 
f/8
f/11
f/16
f/22
f/32
f/40

At the top of its focal length range, we notice that the DA 18-55mm WR is a bit soft at wide open (f/5.6). Sharpness peaks at f/8 and f/11, but then it softens again at f/16 due to diffraction. At f/32 and smaller, it softens significantly, rendering the images unusable.

Verdict

With regards to overall sharpness, the Pentax SMC DA 18-55mm f/3.5-5.6 AL WR does quite well given that it's the cheapest lens in the Pentax zoom lineup. It does show noticeable weaknesses in some areas, as to be expected however. At 18mm, the corners are significantly soft at most apertures, while at 55mm, the wide-open performance leaves a lot to be desired. The focal length sweet spot of this lens happens to be around 24mm to 35mm, where performance was the best. In conclusion, we consider that sharpness is obviously not a strength of this lens, but the lens will certainly get the job done for many users.



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