Thanks John,
I will try that white balance setting. It's very difficult to get away with no filter at all in New Zealand. Our UV levels are horrific - Ozone hole.
I started with a UV filter on this lens but the 1A did seem to make a little difference.
I will try your suggestion but refit the UV filter.

Cheers

Hamdala

I have used this lens for 2 years on a *istD and now on a K100D.
It's build quality is very very good but it is heavy - almost 600g - combined with the K100D it becomes a 1.2Kg brick to carry. Be prepared!!
Being a full frame lens the distortion is low on a DSLR also corner softness
is practically non-existent
Colours are a little cold (compared to the pentax 24-90) but I corrected that (almost) with a 1A filter.
Tends to over-expose ( both cameras) Seems to need correction of -0.7 most of the time (not so much at the 24mm end)
Sharpness is very good throughout the range (even wide open)
It's a bit slow but an excellent daylight lens.
Now agonising whether to take the tamron or the pentax on a 10 week trip
The pentax wobbles badly - doesn't feel like it would survive whereas the Tamron feels like you could drop it and carry on.