Pentax-DA 18-270mm F3.5-6.3 Review

We illustrate center and edge sharpness with 100% crop samples from the center and the right edge of a horizontally framed scene. These samples were shot with a Pentax K-5 IIs at ISO 200 in RAW. We used autofocus for the center shots and for the edge shots we used the setting of the center shot. Our attempts at manually focusing the edge shots came out worse than AF. No postprocessing other than conversion to JPG and unsharp mask 125% radius 1 threshold 0.

We shot all samples at full open aperture and one and two stops down. Note how the center sharpness improves sooner than the edge when stopping down.

The scene:

Click on a thumbnail to open and browse the 100% crop files:

	Center	Edge
18mm F3.5
18mm F4.5
18mm F6.7
37mm F4.5
37mm F6.7
37mm F9.5
80mm F5.6
80mm F8
80mm F11
148mm F5.6
148mm F8
148mm F11
270mm F6.3
270mm F8
270mm F11

This lens is best stopped down at least one and a half to two stops:

The center is quite sharp at all F-stops, but stopped down one stop it becomes excellent for a super zoom. The edges are soft and the lens should be stopped down at least two stops to get the edges acceptably sharp. The exception is at 270mm where we found the edges unacceptably soft even when the lens is stopped down two stops. But the center is nice and crisp.

Cropping

While the 18-270mm is capable of producing great photos, if you really like cropping, don't expect too much from this lens.  Here's a sample 100% crop of a distant subject taken at 270mm and F9.5.

The Verdict

The Pentax 18-270mm is acceptably sharp in the center, but it struggles to keep up in the corners.  Overall, it is pretty good for a super-zoom in terms of sharpness, however.