This reminds me of how things went last Saturday. I was heading up to Mount St. Helens, racing the sun to get late afternoon shots from various viewpoints. I had taken several pictures along the way before rembering that I was shooting at a custom white balance that was wrong, and was set to ISO 800, which of course was wrong.
Fortunately, I was shooting in RAW, so the WB was not a problem, and with the 5D the 800 made no noticeable degredation of quality. Kind of funny in retrospect!
If anyone wants to see the outcome, check out my pbase site linked below (if you click on "Recent" at the top of my home page you will see the gallery down the list) -- Mount St. Helens makes for an awesome day trip photo op!
Tony
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Several Canon cameras, too many lenses and stuff to list 
Tony Long Photos on PBase