Live View
In addition to their reflex viewfinders, both cameras offer live preview via 3-inch LCDs. The “Set” button on the Canon activates its live preview. The Nikon is a bit more cumbersome – live view is lumped with drive modes on the D3X, so the user switches between single shot, continuous, mirror up and live view. When the D3X is in live view mode, the LCD is activated when the user presses the shutter release. The Nikon offers two flavors of the feature, which the user chooses between in a menu.

Canon 1Ds Mk III - Live View Button	Nikon D3x - Live View Button

Unavoidably, live view imposes a significant shutter lag on both cameras, because they add additional mechanical steps. Both cameras can magnify the live view for focus check, and use the same magnification controls for preview as they do for image review. Again, the Nikon is a bit more cumbersome, because the user has to press a button to activate the magnification control. On the Canon, the magnification increase and decrease buttons work directly.

Nikon's live view “Tripod” and “Hand-Held” modes call on different autofocus technologies. Hand-Held uses the camera's regular autofocus system. To focus, if flips the reflex mirror down, blacking out the LCD view while the user holds either the autofocus-on button or shutter release halfway down. Releasing either button restores the view. Pressing the shutter release takes a shot, most of the time. In single-servo mode (when the camera is supposed to focus once, then stay put) the D3X won't shoot if it can't focus. The problem is, with the mirror flipping up and down, the camera makes the same noise and the LCD blacks out the same way, whether it takes a frame or not. Image review is the only way to tell if a shot was taken in single-servo, and that might get confusing if there are only slight differences between exposures. In continuous focus mode, the D3X shoots whether or not it registers focus.

In Tripod mode, the D3X uses data from live view to analyze image contrast as a criterion for focus. The user can choose any spot on the image as the focus point, though Nikon warns that the D3X needs lines parallel to the long edge of the frame to focus, and it can be confused by repeating patterns and other pretty common phenomena. (It seemed to do okay for us.) Nikon also points out that the contrast system is slower than the camera's conventional one.

Here's a point where it's fair to ask if the technology on offer is just a halfway measure. When the D3X is being used in tripod mode, it has many of the drawbacks of a view camera: it will only function properly on a tripod, it must have a static subject, and it's slow. Then why isn't the technology being used to offer more of a view camera's benefits? Why don't these cameras sort out depth of field? Sinar's decades-old film cameras do. Why can't the user tag two focus points, and have the camera determine a maximum aperture and an ideal focus point for getting both points sharp? Why not take another step, and have the camera offer guidance in setting the angle on tilt lenses? This would not be simply a stunt: with focal lengths of 20 mm up to even 100 mm, the smallest apertures available on Canon and Nikon lenses are small enough to degrade image quality. Setting up the cameras to optimize the aperture setting would have a noticeable effect on image quality.

The D3x live view display can show the same information as the viewfinder, plus a histogram and a larger indicator for its built-in level.

Canon offers a single live view mode, and it recommends using it on a tripod. The Canon 1Ds Mark III doesn't autofocus in live view. The users' manual recommends using the 5x or 10x magnification settings while manually focusing. The 1Ds shows shooting data on the LCD in live view mode, with the same control feedback as the viewfinder. Pressing the “Info” button cycles through a range of data displays, including a histogram.

Both the Canon 1Ds Mark III and the Nikon D3X can display their live views on external screens. Canon uses a computer monitor in tethered shooting mode, while Nikon has set up the D3x to feed video via a HDMI cable.

Canon cautions the user about heat build-up in live view. Heat can increase image noise, throw off color and screw up Microdrive memory cards. Canon's manual raises the alarm more than Nikon's literature, but there isn't any reason to think Canon has more of a problem. Both the Canon and the Nikon have thermostats, and can shut down live shooting. The shutdown routines are geared to preserve the cameras' components, not to prevent users from taking shots with too much noise or bad color. Live view requires plenty of power, so the cameras need battery swaps much more frequently in live mode.

Live view has drawbacks that can affect workflow and image quality. We don't envision using it as the primary viewfinder on either camera, even in studio shoots on tripods. There are times when an optical viewfinder is limiting or inconvenient, though: when the viewfinder is hard to reach, when a couple people collaborate on a shot and want to look at it while making an adjustment, and so on. We expect most photographers to rely on the viewfinder, and flip on live view only briefly and that's what we recommend.