Originally posted by Fluegel If Pentax macro lenses perform well at that longer focusing distances or infinity it means performance at close range can be improved.
Well, the performance of any lens 'can be improved', but if you are saying that a lens performing well at infinity means that it is optimized for long focusing distances and therefore will perform worse at close range, then that is not true. It may be optimized for close range, but still perform well enough at long distances to perform 'well'.
Since you have the means to check this yourself, why don't you try it? You have heard from lots of people here who have, and who dispute what you are saying. I am another. We are not going to be swayed by theoretical arguments when our own experience says different.
My (uninformed) belief has always been that it is harder to engineer a lens which performs well at extreme magnifications than at infinity, so macro lenses are generally made to higher specifications in order to get good quality at close range, and this has the side benefit of increasing quality at long range also, even if it is not
optimized for long range. This is really just an educated guess though, which I have arrived at through using lots of these lenses. If it was easy to make lenses perform well in the macro range, then I would have expected to see some manufacturers producing a cheap macro option which is not over-engineered to give good results at longer ranges also, but I never have.