Instantly Switching 1Ds Autofocus Modes

One of the biggest technical challenges in photography is focusing; choosing what element of the image should be the center of focus and locking focus on that element quickly and accurately. The 45-point autofocus system of the 1Ds is fast and usually accurate, but at times it will lock focus on something other than the intended center of focus, especially if there is an obstruction in front of the main subject. In that situation, autofocus can still be used, but it needs to be limited to a single focus sensor so that the camera knows exactly what the intended subject is. In other situations, manual focus may be necessary to achieve the desired effect. Additionally, in low light situations the autofocus system requires more time to lock focus on the subject and the delay this causes can result in missing the desired shot. If the distance to the main subject is not fluctuating, it can be desirable to lock focus and then take multiple shots quickly without any intervening focus delays.

The Canon EOS-1Ds has numerous custom functions that can be used to configure the way the camera works, and they can be set to accommodate all of these situations easily. The first thing to do is to "register" the center autofocus sensor by pressing the AF point selector button (just to the right of the * button), rotating the command dials to select the center autofocus sensor, then simultaneously pressing the X and Flash Exposure Lock buttons. Then set Custom Function 4 to option 1 so that autofocus with all 45 focus sensors is initiated when the * button on the back of the camera is pressed (it's under the tip of your right thumb when holding the camera normally), and exposure lock occurs on shutter release half-press. Next, set Custom Function 18 to 2 to autofocus with center sensor only by pressing the X button. (This button is just to the left of the * button.) With this combination of settings, you can instantly switch between manual focus (don't press any button and turn the focus ring on the lens) autofocus with center sensor only (press X button) and autofocus with all 45 sensors (press * button). The X and * buttons are right under the tip of your right thumb, and with a little practice you can switch between them instantly by touch without having to take your eye from the viewfinder. Not having autofocus tied to the shutter button takes a little getting used to, but the control and flexibility it offers is well worth the time it takes to learn.

If this doesn't seem to work, press X, then press the AF point select button (the button to the right of the * button) and select all focus sensors; the entire outer circle of focus points will light up. Then press the * button and you should be focusing with all 45 AF sensors. You can also use this technique to manually select a single non-center focus sensor and instantly switch between the non-center sensor and the center sensor with the * and X buttons.

UPDATE: This functionality can be duplicated on the Canon 10D by setting Custom Function 4 to 1 and Custom Function 13 to 2.

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The 1Ds and E-TTL Flash.

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