The D4 body gains more curves than the D3S, but remains a muscular looking camera. The top plate arches into the hood more gracefully, and the red triangle below the shutter button has been streamlined into a single line. The camera has a good grip and heft, sitting comfortably in the hands. The shutter release button now sits at a lower angle and rests on a convex instead of a concave surface, which feels more comfortable. Even though its dimensions are roughly the same as the D3S, it's a little lighter with 60g shaved off. Portrait grip is more comfortable and useful, thanks to some changes made in button placement (more on that below).
The buttons on the D4 can now light up, as well as the LCD screens. It's a big help for photographers shooting in dark environments and it's an improvement so obvious we wonder why nobody has thought of it before. To turn on the lights, push the On/Off switch pass 'On'.
The D4 gains the focus-mode selector lever first seen on the D7000. The lever switches between auto and manual focus, while the unmarked button on top of the lever lets you switch between the different AF modes by pressing down and turning the command dials. While we originally didn't love it on the D7000, we've since grown used to it, and it does allow you to change AF modes by feel easily.
The port covers have undergone an interesting change: Instead of several ports covered by a single rubber cover, there are now four separate port covers for the six ports. Now you won't get a huge piece of rubber jangling over every exposed port while you're only using one or two. While seemingly a small thing, it shows that Nikon paid attention to the details while designing the D4.
Speaking of ports, the D4 gains a headphone jack to monitor sound levels, and a gigabit LAN port to connect the camera to a network. The LAN port is compatible with the new WT-5 wireless transmitter optional accessory, which can create a wireless network on which to share images from the D4 and establish remote control of the D4 via an Internet browser. This means you can gain (limited) control over the D4 using any computer with a browser, including tablets.
The top plate has also undergone a few welcome changes. The front-facing part of the release mode dial is now covered, making the camera look cleaner and less cluttered. While that might mean less of the mode dial to grip, we find that it doesn't degrade the user experience in any way.
The D4 gains a new dedicated video Record button, to the right and back of the shutter release button. It's smaller and sharper in feel than the Mode and Exposure Compensation buttons which share the top right of the D4, making it easier to distinguish. Should you accidentally press it while shooting stills, nothing will happen – it will only start movie recording if the D4 is in video mode and in Live View. The Record button can also be customized to trigger a limited selection of commands, like ISO sensitivity, in stills mode.
The back of the camera sees the most changes. The D4 has two joysticks on the back of the camera, which add as new sub-selectors. Just like on high-end Canon DSLR cameras, the joysticks are used for AF point selection, similar in function to the bigger d-pad, so you can use either to shift the AF point. The joystick also serves as a focus lock – once focus has been achieved with a halfway press of the shutter, pressing the joystick down will lock focus. Whether you use the d-pad or the joystick will be a matter of preference, but as reviewers who have used both Nikon and Canon cameras, we quite like using a joystick to move the AF point, as we find it easier to shift than the larger d-pad.
While some long-time Nikon users might not like the joystick situated above the d-pad, we think they'll welcome the one found lower on the body for use in portrait mode. While holding the camera vertically, you no longer have to reach for the d-pad, as the second joystick is easily in reach of your shooting hand's thumb, helping you shift AF points easily. A thumb-rest on the bottom of the camera makes holding the D4 in portrait mode much more comfortable, and there's an additional Fn button to the back of the vertical shutter release. The only gripes we have with the vertical grip are that the Fn button is rather small, and the front command dial is quite stiff.
Instead of two ConpactFlash card slots, the D4 has one CF and one XQD memory card slot. While XQD cards are smaller and have read/write speeds faster than CF cards, Sony is the only company producing them at the moment. SanDisk, Lexar and Kingston have publicly announced that they have no plans to make XQD cards at this time, making Nikon's decision to include it in the D4 look premature. As it is, it forces professionals to switch from an existing inventory of memory cards to a new standard if they wish to make the full use of the D4's dual card slots.
Due to new battery regulations in Japan, the D4 comes with a new battery model, which is different from the one found on the D3S. Nikon says it performs better than previous batteries at low temperatures and is rated for 2600 shots per charge according to the CIPA standards (the D3S' battery was rated for 4200 shots).
The D4 comes with two auto-focus modes and four AF-area modes. They’re switched by pressing the unmarked central button on the focus-mode selector level besides the lens and turning the command dial. Because the changes will be reflected in the viewfinder, photographers can now change AF modes without taking their eyes off the scene.
AF-S (Single) is best for stationary subjects, the focus locks when the shutter button is pressed halfway. AF-C (Continuous) is best for moving subjects; the camera will focus continuously as long as the shutter button is pressed halfway.
The four AF-area modes are Single-point AF, Dynamic-area AF, 3D-tracking mode and Auto-area AF mode. Single-point AF is best for precision focusing on still subjects. Dynamic-area AF lets you choose from nine, 21 or 51 AF points. The selected AF point and its surrounding points will cover the wide, specified area to limit focus to. 3D-tracking AF maintains tracking of subjects by automatically shifting focus according to the subjects’ movement. It can also compensate for the camera’s movement, making it an ideal AF-area mode for users who like to center focus and recompose; the D4 will shift the AF point automatically to ‘track’ where you focused on. Auto-area AF uses all focus points to focus automatically.
We found the D4's auto-focus to be highly dependable, focusing quickly and accurately in almost every situation we threw at it, from stationary subjects in bright daylight to fast moving subjects in low-light. While Nikon says the new AF system should put priority on faces, we found that the camera's AF will, in some situations, place priority on near subjects over further subjects with recognizable faces. The D4's ability to track faces is more obvious in Live View, where a focus box will appear over a subject's face.
Unlike the Canon EOS 5D Mark III which we reviewed recently, the D4 doesn’t clutter up Live View with unnecessary info. Unlike the Mark III however, while you can monitor and change audio levels before recording, you cannot change audio levels after you hit record.