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Old 04-11-2009, 06:19 PM
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troypiggo (Troy)
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troypiggo is offline
 
Join Date: Nov 2008
Location: Brisbane, Australia
Posts: 4,846
The difference between f/2.8 and f/4 is one stop. That's double the exposure time for all the other setting remaining the same. But if you want to keep your exposure time the same at 30secs, you'd need to double the ISO. Like I said, the 5DII should handle that. Plus, keep in mind the exposures will be comparable to the f/3.5 you were using anyway. Plus plus, not many lenses are sharp as a tack wide open, so you probably could/should have stopped the 16-35 down to f/4 or so anyway. You might stop the 17-40 down to f/5.6 for sharper image? You'd need to test that. Playing with the ISO's is the solution, because you're locked in on max times, and you're going to be f/4 or f/5.6 or in between.
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