Nikon D300S Live View

The Nikon D300S retains the Live View functionality previously featured in the D300 and is almost unchanged. The only significant differences are found in the physical controls, and the available information displays.

A very welcome enhancement to the Nikon D300S's Live View mode is its one-touch activation, via the Live View button. On the D300, Live View mode had to be selected via the Drive Mode wheel on the left side of the camera's top panel; a somewhat cumbersome arrangement. By contrast, the Nikon D300S sports an Lv button on its rear panel, in somewhat cumbersome reach of your thumb. Press it at any time and the mirror flips up and the camera enters Live View mode. It's an arrangement we've previously seen on the D90, and it does a lot to make Live View a much more fluid part of your photography than it was in the past.

The second feature carried over from the D90 for the Nikon D300S's Live View mode is the optional full information display. The Live Mode shooting info display shows you a lot of what you'd normally see looking through the viewfinder, yet manages to keep most of the information out of the way of the live image area. Information displayed includes current metering mode, shutter time, aperture, exposure compensation, ISO setting, shots remaining, exposure mode, file mode (RAW or JPEG), and white balance setting. It also shows microphone status and minutes/seconds of movie recording available at the current resolution and quality settings. There's also an optional gridline display that helps in precise subject alignment, and a newly added virtual horizon overlay that assist in getting the camera perfectly level in two axes.

Nikon D300S Live View Data Displays

The Nikon D300S's Live View display includes a good bit of relevant shooting data, including shooting mode, autofocus mode, image size, image quality, white balance, audio recording, time remaining, metering mode, shutter speed/aperture, exposure compensation, ISO, and more.

Pressing the Info button cycles through the four available display modes. This display shows the minimum amount of information, only overlaying the focus area. Not shown are "no card" and low battery warning overlays, which appear on all displays when active.

New additions include framing guides...

...and the nifty virtual horizon function.

One thing we miss in the Nikon D300S, though, is the live histogram display that's an option on the Nikon D3 and on some competing SLRs from Nikon's arch-rival Canon. A live histogram would have been especially useful because the D300S's Live View display does not actually simulate exposure. Live View will show the effect of exposure compensation applied to Program, Shutter, and Aperture priority modes, but you get no preview of over or underexposed settings, nor is an analog exposure meter shown in the Live View display. The aperture and shutter speed shown at the bottom of the display are the values that were set when Live View mode was enabled; they are not continuously updated in response to lighting changes like they are in the viewfinder or LCD panel when Live View mode is off (if Live View is active, the top Status LCD is also not updated with new automatic settings as lighting changes). This implies the D300S always uses the dedicated 1,005-pixel RGB metering sensor for determining exposure regardless of Live View mode, and doesn't attempt to meter using image sensor data (except while recording video). In Hand-held mode, the exposure values are updated after autofocus, because the metering sensor is briefly active during AF. But in Tripod mode, exposure values remain static even after focusing. Tripod mode assumes the lighting has not changed, so it really is designed to be used in a studio environment where lighting is controlled. This means it is possible to capture improperly exposed images even though they looked fine in the preview, if you're not careful. Of course, the aperture and/or shutter speed values will update in response to the user changing them via a command dial.

Like the D300 before it, the Nikon D300S provides two modes for autofocus operation. Handheld mode uses the camera's dedicated phase-detection sensor. Tripod mode, meanwhile, uses contrast detection on a feed from the image sensor. As Nikon's naming clearly suggests, Handheld mode is the more useful of the pair for shooting handheld and/or moving subjects, since the AF operation itself is faster. Tripod mode is more useful for static subjects with the camera mounted on a tripod, offering two main benefits: you can move the AF point anywhere you want within the frame area, and front- or back-focusing issues shouldn't come into play. Unlike the D90 and some of the competition, the Nikon D300S does not offer a face-detection focusing option.

Nikon D300S Live View Contrast-Detect Autofocus

One advantage of contrast-detect AF is that you can put the AF box wherever you like it. When focus is locked, the focus box changes from red to green.

By way of explanation, the phase-detect/contrast-detect distinction is one of the fundamental differences that separates digicams from digital SLRs, and is the core reason that SLRs focus more quickly. Contrast-detection autofocus involves looking at the image from a camera's main image sensor and evaluating it to see how abruptly brightness values change from one pixel to the next. If an image is soft and fuzzy, brightness changes between adjacent pixels will be relatively slight, but if it's sharply focused, they'll be much greater. The point of ideal focus is found by moving the lens elements back and forth and determining whether the contrast signal gets stronger or weaker. Achieving focus this way necessarily involves some back-and-forth hunting, which can take a while to accomplish, since there's no indication as to how close the camera is to focus nor which direction focus needs to be adjusted.

Hand-held mode. The phase-detection AF array is shown in Hand-held mode, very similar to the optical viewfinder. Unlike contrast-detect mode, the red focus area box does not turn green when focus is achieved. Otherwise, the displays available in this mode are very similar to Tripod mode.

By contrast, phase-detect AF uses a system of prisms, lenses, and a secondary sensor to determine not only whether the image is in focus, but by how much it's out of focus and in which direction. The camera can then adjust the focus setting to exactly the position needed in a single step. As a result, phase-detect AF systems are generally much faster than contrast-detect ones. The catch with phase-detect AF, though, is that it requires some of the light passing through the lens to be diverted to the focus sensor. This is fine in an SLR when the mirror is down between exposures, as part of the mirror is typically partially transmissive, with the light passing through it deflected by a secondary mirror down to the AF sensor, usually located in the bottom of the mirror box. When the mirror is raised in Live View mode, though, light from the lens can't get to the separate AF sensor. This makes Handheld mode's AF operations rather lengthy (and noisy): To focus the camera the mirror has to be dropped, focus determined, and the mirror raised again, adding several tenths of a second to the normal non-Live-view shutter lag.

As an example of the relative speed of each mode, when we tested the Nikon D300S in the lab, we measured a shutter lag of 0.225 second when using the optical viewfinder and a single AF point. This increased to 0.473 second in Live View mode, all other settings being the same. In contrast-detect AF mode, it took an average of 2.5 seconds for Tripod mode to determine that the lens was in focus, even when starting with the lens already focused on the target. (It can easily take several seconds for the camera to slew a lens from infinity to close focusing in this mode.)

In Tripod mode, the Nikon D300S provides up to a 13x magnification in Live View mode, centered around the focus area, providing excellent focus discrimination when focusing manually. This is pretty important, as less than about 10x magnification really doesn't do the trick for getting the focus set right, but at 13x we could nail the focus every time. In Hand-held mode, the amount of magnification available is limited to 3x.

The Nikon D300S also offers 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. What's more, you can do it via cable or Wi-Fi connection, with the optional Wi-Fi adapters. The D300S requires Nikon's optional Camera Control Pro software to enable this feature. Software for a similar feature comes bundled with Canon's SLRs.

Despite the improvements over the D300, we think the Nikon D300S is still lagging some of its rivals when it comes to its Live view implementation.

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