when they chop onions they don't stand over them like other food.. they step back a little so they don't breath in the smell/ stopping the crying!! also a very well air conitioned/ventilated room as per shown on tv will ease the tears.
or if tht fails just good editing!! another tv trick to make us real chef's at home feel lousy!
It's due to having very, very, very, very, very, very, very sharp knives - they start by taking off the ends then put 2 cuts down then slice across......at least that's how it's taught at catering college....with a very, very, very, very, very sharp knife!! That's all there is to it.......
If you soak onions in water for some time, they lose the gas(?) that makes your eyes water. This also makes it easier to chop the softened onions, given you have a very, very, very sharp knife in hand.