Anyone know of a site or other source of information on C41 processing problems from the perspective of purchasing processing services? I have been using Portra 160 and having it processed locally. I am scanning the negatives and printing on an inkjet. I am not getting the highlight through quarter tone (zone IX-IV) value separation that I want. Also my images could be sharper and I have a bit more grain than I think I should have.

I am overexposing a bit (indexed at 100) to get the shadow values I want but I think this small amount should not, if the processing is correct, create these other problems. I did have a few rolls processed by another lab and things seemed a little improved, though if so it was not dramatic.

If I were making color prints on an enlarger what kind of density would I want for zone VIII?

All of my lenses are modern multicoated and well respected brands/designs. I am using a tripod that exceeds my needs.

Any info and insight appreciated. Thanks.