You're going to walmart, their printers are crap.
A Frontier is a Frontier, and they're not crap. I've gotten prints made in probably a dozen Walmarts and every single one has been out of a Fuji Frontier on Crystal Archive (granted the bulk CA, but still.)
Walmart employees no nothing and chances are that printer has only been "serviced" once in the past 5 years by a "technician" who apart from a bullet point list of how to "calibrate" the specific printer Walmart uses, knows nothing about technology.
I've watched the Walmart near me run test strips more often than most mini-Labs I've used. Walmart is big enough to be good at process and procedure. and I can't imagine that one store runs a Frontier any differently than another in terms of tests or settings.
It is much more likely that the OP has their monitor set too bright- after all, Walmart will reprint bad images and you'd expect with their volumes that they don't want to reprint thousands of pictures a day because the Frontier isn't set up correctly.
A few years ago I was totally spoiled by the local Walmart because one of the techs there would print my output right after a chemical change-- but even outside of that, I have gotten prints for friends made a their local Walmarts up and down the East Coast for the last 10 or so years, and I've had to have reprints twice- and that was because the Frontier had a roller issue that left a small line on the print.
That's out of thousands of 8x10 prints. The first time was a hardware problem the store I was at couldn't fix (and they refunded on the spot and I reprinted at a different store an hour later with no issues.)
The only other issue i had was a print that *was* too dark (I was away from home and on a non-calibrated friend's system) and they reprinted that image brighter (the "rule" used to be if you didn't pay for the order online, then they'd happily reprint at the store.)
Paul
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Image
thats one of the pictures that came out really dark
http://flic.kr/p/bvbump
The whites are overexposed, it's entirely possible that the Frontier's autocorrect is hurting that- just ask them to reprint it lighter.
Paul