Hey does anyone in here using the XSI know how to use the BULB shutter speed setting so you dont have hold down the button....

I thought you could just press it once to open and then press again to close but for some reason I have to hold down the button which seems useless... is there an option in the menu for how BULB works that I can change or does it have to be in a certain mode?

oh and... XSI 50f1.8 , kit18-55, next lenses in order --> 70-200f2.8, 24-70f2.8, 10-22f3.5, 100f2.8 macro