Thanks Richard!
Ok, here is the test:
k10d and Pentax 18-250 at 18mm, 50mm, 100mm, 250mm
k20d and Pentax 18-250 at 18mm, 50mm, 100mm, 250mm
k20d and DA* 50-135 50mm, 100mm
Not entirely scientific. Handheld (with 1/500 shutter speed and SR on however). k20d images are 20% "bigger" in dimension at 100% due to increased resolution.
All original files are here:
k10d and k20d DA 18-250 and DA* 50-135 - a set on Flickr
I am showing the crops since that is the only place I think you will see major differences. All were cropped from highest res images viewed at 100%. I think those with a k10d and/or an 18-250 lens will be pleasantly surprised.
18mm 100% crop, k10d, k20d
250mm 100% crop, k10d, k20d
50mm 100% crop, k10d 18-250, k20d 18-250, k20d DA* 50-135
100mm 100% crop, k10d 18-250, k20d 18-250, k20d DA* 50-135
It is clear that the DA* is a sharper lens, but the 18-250 is still great, and very versatile.