For most working photographer, semi-auto setting (Aperture Priority, Shutter Priority and Program Mode) is the best option to freeze moment. Some ask me, “Is metering applicable in Aperture Priority, Shutter Priority and Program Mode?”
Up to my understanding, I believe it is. The key points to remember are as such: First, always bare in mind that the camera will set the exposure based on the light you point-at. Second, in even-light condition it will almost give you good exposure, provided that you know how or which metering pattern that suits to the situation or subject (light). But in tricky-light, you should know how to override the semi-auto setting into Manual mode on-fly.
When working outdoor say taking photograph of your client rafting here in very high contrast Kiulu river in one fine day (if you don’t know where Kiulu is, Google it 🙂 ) your chances to get the desired moment is merely within one single click. So if you didn’t get the exposure right or you don’t understand how your camera deal with light.. your photo would be either overexpose or underexpose, it is because the very bright white water surface will fool your camera sensor, as result your photo will become underexpose or the dark river bank will cause your photo become overexpose and here are some examples on how I experiment metering on Aperture priority semi-auto setting at Kiulu River near my house.
In white water rafting business, some of these tourists perhaps will hire you as their photographer while they are having a jolly good time bouncing along Kiulu river. Most of these tourists want the photos just before they leave at the ending point, where your time is just enough to transfer all the photos into CD and deliver it to them. So if ( I repeat) if you are thinking of using any enhancement software to correct the exposure, sorry man…but you just lost the business 🙂
Hopefully it helps. Oh FYI I’m not one of these tourist photographer. I was just wasting my bright sunny day, enjoying the company of some adrenaline junkies… after all this spot is just behind my house 😉