A reader asks: "I have a problem with my digital camera. When I shoot an off-center subject, the camera focuses on the wall behind them. How can I make the camera focus on what I want?"

Many digital cameras focus on whatever is in the very center of the viewfinder or LCD screen. So, if your subject isn't there, the stuff behind (or in front) of them will be nice and sharp, but it won't.

One time to really watch out for this is when you're photographing two people cialis prescription online standing side by side. You have a person on each side of the viewfinder, but the sensor is busy focusing on the wall behind them.

For example, take this photo of two chairs I just shot in the basement (sorry, I was the only one around, so I couldn't get any actual people to pose):

In this close up, you can see how the camera focused on the wall behind them (gasp!):

Ah, but not to worry. There's an easy way around this little problem!

Most digital cameras have a feature called "focus lock." The vast majority of these activate when you press the shutter release half way down and hold it there. Usually, there's some sort of light to indicate you have sharp focus (and this light is usually located next to the viewfinder and glows green when the image is properly focused).

So, all you do, again with most cameras, is move the camera so your subject is temporarily centered, press part way down on the shutter release to lock in the focus, hold the button in position as you recompose and finally, press the shutter release the rest of the way down.

In this instance, I just centered one of the chairs, held the focus lock, moved the camera back to the composition I wanted and shot.

Note that if you let up on the shutter release at any point in this procedure, you'll lose the focus lock and have to start over.

As always, consult your owner's manual for specifics, but this is one procedure that seems universal for most digital cameras. Happy shooting!