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This is quite simple to me, the Olympus 45 F/1.8 is not a macro lens the Panasonic 45 F/2.8 is a macro lens. This is the difference at minimum focus distance with both lenses. The Panasonic is the winner as a macro lens the Olympus 45mm is a MUCH sharper, I.E. better image quality than the 14-52 kit lens and a much faster lens. Both in AF speed and Aperture. Each would be useful for difference reasons. The 45 macro would be the better overall choice in most cases for underwater use. The Olympus 60mm macro coming later this year will be even better.What would you recommend for a macro lens, Scott? That will come after I house the e-pm1, tho.
Troy, it looks like Phil has covered this pretty well. Like he said, I'd get the Panasonic Leica 45mm macro lens, or the Olympus 60mm macro lens if you can wait until later in the year.
Scott