Prompting smiles from subjects has been a major exercise for photographers since people began snapping pictures, but it hasn't been until now that a camera maker has tried to do something about the problem. Sony introduced two cameras yesterday that have "smile shutter" technology that's supposed to automatically detect and capture a subject when they smile. The DSC-T200 ($400) and its cousin, the T70 ($300) are expected to go on sale next month. Both bytesnappers have maximum resolutions of eight megapixels, but the T200 has a larger display than the T70-3.5 inches versus 3 inches-and a larger optical zoom-5x versus 3x.