Magic button

I wonder what's that little green button for when I first got my Pentax K10D. The answers are all in the manual, but what does it really do in practical, I asked? Imagine this...you setup your K10D for a studio photography session, which is typically set at Manual Mode, with the corresponding shutter and aperture settings as per lightmeter readings. After the shoot, you head to the nearest cafe to relax...then something happen across the street, maybe an accident or some events which caught your attention. You grab the camera from the bag, and head to that direction. Turned it on, and frantically snapping away...only to find out a second later that all the shots were either severely over/underexposed. You blamed yourself for not having set the mode back to P or A, but the moment's gone. Hmmm....

Here comes the greeny little button...after switching on the camera, just press it momentarily while focusing at the scene, you'll get a perfect exposure as metered through the lens. Wow! Nice little touch, how come other manufacturers never though about this?

Well, Pentax did...;)