I wonder why the DA 18-135 has so little credit at photozone

Photozone ratings are a little awkward. They gave the 18-55 WR a three star rating and the 18-135 one and a half. Now, look at this figures:

18-55 vs. 18-135

The green cells tell the lens has better resolution than the other, and viceversa.

It is true that beyond 50mm the corner resolution of the 18-135 drops very low, but the center resolution keeps high values. You can think of the 18-135 as a better kit lens up to 50-60mm, with an added extra tele range with very good center resolution values. You should get very good IQ at these focal lengths as long as your subject is in the center of the frame, wihch happens most of the time shooting tele.

So, appart from cost considerations, why 3 stars for the 18-55 and 1.5 for the 18-135?

P.D.: The values are from the PZ site

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Saludos, Carlos.