Bank of Hawaii (NYSE: BOH) reported its second-quarter earnings yesterday. I haven't run the numbers on it yet, but the bank is a favorite of my fellow Fool Anand Chokkavelu, because it operates in a good market and didn't make crazy loans when everyone else was.

Interestingly, B of H missed analysts' earnings estimates by $0.04, yet investors barely shrugged. That's odd. Normally, investors freak out when a company misses estimates. And this, my Foolish readers, is a sign of just how weird the world of banking stocks is right now.

For a great many bank stocks, there's a pretty clear relationship between the percentage of nonperforming loans that the bank has and the book-value multiple that investors award it. Sport a lower percentage of bad loans, and your stock will get a book-value multiple of 2 or higher. Show that you're drowning in soured paper, though, and you'll be lucky to see investors willing to pay full book value.

To illustrate:

Bank

Nonperforming Loans / Total Loans

Price-to-Book-Value

Bank of the Ozarks (Nasdaq: OZRK) 0.7% 2.4
Bank of Hawaii 0.7% 2.2
Signature Bank 0.7% 2.5
Regions Financial (NYSE: RF) 4.3% 0.6
Doral Financial (NYSE: DRL) 12.1% 0.5
Synovus Financial (NYSE: SNV) 4.8% 0.8

 Source: Capital IQ, a division of Standard & Poor's.

For the most part, the "good" banks can do no wrong -- as in B of H's quarterly earnings -- while the bad banks can do no good.

To be sure, there are other factors at play here. Hawaii is a better market to have been lending in than Florida. Banks with largely fixed-rate, low-loan-to-value residential loans are preferable to banks with huge exposure to construction and home equity loans. But if we're looking for two simple numbers to gauge bank performance and investor sentiment, these will do pretty well.

Now here's the rub: I said that "for a great many" bank stocks you can see the nonperforming loan-book value multiple relationship. But not all banks. And I think that among the bank stocks that don't fit into that relationship, there could be some good opportunities for investors.

Take Huntington Bancshares (Nasdaq: HBAN), for instance. Investors got slaughtered in the fallout of the housing meltdown as the bank reported billions in losses in 2009. Today, though, it's profitable again, trading at just above book value, and it has a nonperforming loan percentage of just 1.6%. BB&T (NYSE: BBT) is one of my favorite midsized banks, and it's trading at 1.1 times book value despite having a none-too-terrible 2.1% bad loan percentage.

Don't assume you can just blindly grab, though -- you do need to do some work. United Financial Bancorp might seem like another good example, with a price-to-book-value of 1.1 and a bad loan percentage of just 0.9%. However, a look back over the bank's historical performance shows that, credit crisis or not, this bank always had very lackluster performance.

The bottom line, though, is that you shouldn't be too quick to write off "bank" as a four-letter word. There are some great banks that are priced like great banks. There are also some pretty lousy banks. Then there are some pretty good banks that are priced like pretty bad banks that may be great performers in the years ahead.

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Fool contributor Matt Koppenheffer has no financial interest in any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or Facebook. The Fool's disclosure policy prefers dividends over a sharp stick in the eye.