Nikon D3 Operation
Nikon D3x Live View Mode
Perhaps triggered by Olympus and Panasonic in the consumer SLR space, "Live View" mode on digital SLR cameras seems to be becoming more common. In the professional space, it's probably less driven by the convenience of framing on an LCD than it is by the need for a viewfinder display when the camera is operated remotely.
We recently saw a Live View mode on Canon's 1D Mark III model, where the mirror can be flipped up and a full-color image from the camera's CMOS sensor fed in real time to Canon's remote control software via USB, Ethernet, or even WiFi. Canon's just-announced EOS-40D and 1Ds Mark III also both sport Live View modes, with a few enhancements beyond the capabilities of the 1D Mark III.
With the advent of its CMOS sensor, the Nikon D3x and D300 both now feature Live View modes of their own. (MOS sensors appear to be a requirement for Live View in DSLRs, probably because clocking data off a large CCD is too inefficient and power-hungry.) Here again though, Nikon has gone the competition one better, by providing what seems to be the most useful and usable DSLR Live View mode yet.
What makes Nikon's Live View mode so uniquely effective are the two options it provides for autofocus operation. The first mode is the one used by everyone else. Because the traditional AF sensors are blocked when you flip up the mirror for Live View mode, you have to drop the mirror to focus, then flip it back for Live View. Canon, Nikon, and Olympus all have this mode.
Nikon Live View with Contrast-Detect AF active
The real trick comes in Nikon's second Live View (Tripod Mode) autofocus option. In this mode, the camera performs contrast-detect autofocus, just like any point & shoot digicam. That is, it reads data off the CMOS image sensor and evaluates how abruptly light to dark (or dark to light) transitions happen on the image plane. Contrast-detect AF isn't nearly as fast as phase-detect, which is why the shutter response of most digicams is so much slower than that of most DSLRs, but the camera can focus without interrupting the Live View display. As an added benefit, because it's working with data coming from the main image sensor, you can move the AF point anywhere you want within the frame area, right out to the extreme edges.
In the screen shot above (apologies for the poor quality, it's a grab from a Nikon presentation), the green rectangle shows the area being examined to determine focus. This area can be moved to any part of the frame, right up against the top, bottom, left, or right sides of the image area.
In all their discussions, Nikon emphasized that this mode was only for use with stationary objects, and with the camera on a tripod. I did get to play with a D3 in Tokyo, though, and found that this system, while vastly slower than the D3's normal Phase-Detect AF, is actually quite usable when the camera is being handheld. We'll obviously do tests on shutter lag in this mode once we get a production sample of the Nikon D3 here in our lab, but I was getting shutter delays of about 0.8 second, shooting in normal office-level lighting. That's slow (you basically turn your $5,000 DSLR into a slow point & shoot), but it didn't seem to be nearly as bad as Nikon was making it out to be. (Probably wise of them to undersell its capabilities, though.)
This is another situation where a solution seems obvious once someone's mastered it. One has to wonder why Canon didn't provide a contrast-detect AF option as part of the Live View mode on their new EOS-40D and EOS-1Ds Mark III.
The D3x and D300 also provide up to a 10x display zoom in Live View mode, providing excellent focus discrimination when focusing manually. This is key, as less than 10x magnification really doesn't do the trick for getting the focus set right; but in playing with the camera at 10x, we felt we could pretty well nail the focus every time. What's particularly interesting is that you can continue doing Contrast-Detect AF when you're zoomed: The green AF rectangle expands to cover the same area of the subject, and you can easily confirm focus on the high resolution screen.
Both the new Nikons and Canons include the ability to control the camera from a computer remotely, and that includes receiving a Live View image from the camera. You can focus, adjust settings, and fire, all from a computer. Nikon's new Camera Control Pro software is necessary to enable these functions, which work over wireless or wired connections. Price for Camera Control Pro has not yet been announced.