Our staff recently started using the Canon EOS 1D Mk IV cameras.  I was pleased to see a rarely recognized feature of the EOS 1D line continue to make an appearance in their flagship camera.

When shooting sporting events outdoors, there are often areas of the field lit differently.  Part of the field may be in direct sunlight, part in shadow and the ball could go anywhere.  What to do?

I usually shoot in a manual exposure mode so the background doesn't affect the exposure, but it's tricky to spin the camera dial several f-stops to account for harsh lighting differences in the time the ball hits the bat and when the fielder reaches it.

This is where a seldom-talked about feature of the Canon 1D cameras comes in.  This feature has been in the lineage since the venerable EOS1D Mk I but it seems not a lot of people know about it.

I realized this when USA Today photographer Bob Deutsch was in town for the 2006 World Series; he's usually very on top of new technology but he didn't know about "the button."  I showed it to him and we joked about calling it "the Chris Lee button" since not even Canon reps seemed to know about it at the time.

No surprise as the manual only has a short description buried amongst dozens of other preferences and on the camera it was hidden in a special "personal function" menu.  For the Mk I and Mk II, there was an obtuse sequence of button pressing to activate it.

But on the new Mk IV, it's been elevated to the regular "custom functions" menu and can be found at C.Fn I: Exposure, option number 14.

Here's what activating this option does: It assigns one of the "back buttons" (where your thumb usually rests) to be a momentary exposure toggle.  Pressing it switches your exposure to a preset value, let go and you're back to the original exposure setting.

To set it up, first you register the desired momentary settings in the custom functions menu, for example a shade exposure of 1/500 at 2.8.  Then change your exposure to your primary setting (say direct sunlight, 1/2000th at 4.0).

You start shooting with your regular back button autofocus in daylight.  When the play moves to a shady part of the field, just move your thumb over to the other back button.  Every time you press it, the camera will switch exposures and autofocus at the same time.

Not only can you set manual values for aperture and shutter speed, but you can also change exposure modes.  I usually like to leave my alternate exposure at "Aperture priority, f/2.8," kind of a safe setting for ensuring you get something while favoring the highest shutter speed possible.

The "Chris Lee Button," pass it on!