Which is the better digital Camera brand _ Sony or Nikon or Olympus?

Which is better...a tank or a corvette? It all depends on what you want/need.
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For high-end digital(SLRs): While Olympus has put forth a decent effort in their first attempt, Nikon and Canon are really the only brands that professionals take seriously at this point.

For basic point & shoot, and mid-to-high-end "prosumer" models: I've heard good things about all three brands. I have a friend who swears by Sony. I tend to prefer Nikon...though Fuji, Canon, and Kodak models have caught my eye too.
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Essentially among the three brands you mentioned, in anything less than a pro-level SLR camera, "better" can't be determined by a simple brand vs. brand shoot-out.
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Some have video, some don't. Some have manual settings, some don't. Some have wide/tele accessories, some don't. Some bring out white detail better than others. Some are more color-true than others. Some are smaller and more convenient than others. Some are larger, but provide better quality. Some take rechargeable AA batteries, while others take only expensive brand-specific custom batteries. Some look sleek and impressive, while others aren't meant to be noticed at all. Etc...

As you can see..."better" depends on what you want....which depends less on the brand...and more on the specific model of camera you look at within those brands.

all three are good........

SONY

although sony makes great products like t.v.s its really between nikon and olympus. i think nikon,is the better one considering they have been around longer,they would have the better reputation.but if your looking to get yourself a digital camera why not give Cannon i try they have better camaras than sony,nikon and olympus and at resonable prices too. here are a few links so you can compare features and prices. Right now Cannon,Sony,Nikon,and kodak are the top digital cameras on the market. olympus is a good camera but it falls in the 2nd best catagory which is Olympus,fuji,Minolta,Vivatar.

absolutly the best digital camera ever is CANON,
for serius shooters powershot series "G", for pros "EOS 20D" or higher