Going to Wal-Mart is the first problem. In my experience they pull
some guy out of the stockroom and say, "You are running the photo
department today!" This is an exaggeration, but I don't find
photo-processing gurus there, more like clerks. I have found some
good people at some Ritz and Walgreens stores though, who do a
pretty good job with their Fuji Frontiers.
Actually, nowadays with the Frontier (and similar), printing
systems, you can get very good, consistent results from Walmart.
Actually, in some cases, because they do a high volume, you can get
better prints, because their chemicals have to be changed
regularly. Assuming the store does this, it is amazing what can
happen, even with totally unqualified people running things.
Now, things are so automated, it takes the processor out of the
equation to a large degree. What counts more is how regularly they
change their chemistry and how diligent they are in their upkeep.
I actually know a pro wedding photographer in Vancouver who has
moved away from her pro lab and gone to Costco, simply because with
the proper profiles, she is getting more consistent results at
Costco. Of course, while she is having prints made, she can also
get an oil change, buy a BBQ and pick up condoms for the weekend