Why is the EM5 so much more popular than the GH3?

I think a better statement is that with the m43 you go out with "pockets full of lenses" :-). I have a little E-PL2 that I use when I don't want to carry my DSLR around, the lenses for it are so much smaller. The camera, 17mm prime and 14-42 zoom all fit easily in my jacket pockets or small bag.

I guess to put it another way, there are days when I want to enjoy the process of photography: setting up the tripod, bringing out the big glass, fiddling with the settings, selecting the perfect spot, patiently waiting for the moment when the light is just right, etc..  On those days I love taking out the DSLR.  Then there are other days when I'm out enjoying other activities and a DSLR, even with a single lens, is just too cumbersome (restaurants, crowded markets, walking the dog, etc..), on those days, my m43 is a better option, I can toss it in a small bag or the wife's purse and not have to think about it too much.

The beauty of the EM5 is that it seems to be capable of addressing both of these situations.

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Before you can start taking good photographs, you must first learn how to recognize bad photographs.