Here is some of the Nikon D4 Q/A's
@IR_Lab Nikon D4 Question: Minimum increments of aperture change during video recording?
(Steve Heiner) - For video, this is where the D4 will really impress. When recording to the internal memory cards, the same option to change aperture exists, changing the aperture in 1/3 stop increments. We've added a new feature called Power Aperture, in Live View mode, though: Using the Preview and Fn buttons on the front of the camera, you can smoothly and steplessly open and close the aperture in Live View mode (prior to recording). If you're recording to an outboard recorder via the HDMI port, you can do this smooth aperture change during recording. (Note that Power Aperture only works during Live View mode.)
Is there any improvement over the D3s in terms of ISO in the range of 3200-12800?
(SH & Lindsay Silverman, Nikon) - I can't tell you quantitatively that it's better by a given amount, but based on what I've seen from a pre-production camera it's every bit as good as what we've seen from our D3S camera, and possibly even better. The processing in this camera is the most sophisticated we've had in a camera to date. Based on the input from the photographers who shot our brochure, they were really impressed with all aspects of the camera, including shooting in low light at high ISO.
@IR_Lab Why is the new D4 battery rated to so few shots compared to D3, D3s, D700, etc ... via @nikonrumors
(SH) On the battery, I don't know the specifics, but do know that regulations in Japan have changed, so the maximum amount of energy that can be stored in a camera battery is less than was once allowed. The D4 is very energy efficient, though. My own experience is that the D4 performs really well in battery efficiency; I haven't felt at all limited by it.
Can you have a histogram up in live mode?
(LS) Yes there's a histogram in both live view for stills and live view for video and it's easily selected using the info button.
From Pyriphlegethon: Every video enthusiast is wanting to know: How is the scale of FX video to 1080p accomplished? Is any line-skipping involved? Noticeable quality drop from the direct-pixel for pixel crop? Only an 8-bit HDMI out?
(SH): The exact details of what we do the distilling down from FX to 1080 is proprietary at this point. I can tell you that there is also a new mode that crops the sensor to give 1080 video using actual sensor pixels. (It's about a 2.7xcrop factor, so you also get a nice "digital tele" effect; potentially handy for sports and nature photography.) (SH) Another comment on video quality is that with the EXPEED 3 processing, we're using real-time noise reduction during video recording (a first for Nikon), and we're also employing "B-frames" in the H.264 codec to improve video quality overall. This applies to all modes and crop factors.
Why the decision not to store the still images from the timelapse feature?
(SH) If you use the interval mode, you can save full-res images, then face a ton of post-production workflow. Intervalometer function speeds this up and automates it, but doesn't allow you to save the stills as well.?. (LS) D3 was a groundbreaking camera because subject tracking was used for the first time to track a subject's color using the 1,005 RGB sensor. D4 improves on this by using 91,000 RGB pixels to subject-track. Additionally, the 91K RGB sensor improves on auto-exposure, auto WB, and i-TTL Flash. According to the photographers who shot for our brochure, they thought the overall performance was improved.
Do you expect to offer more video codec options, such as intraframe-only compression and possibly even uncompressed video to the XQD cards?
(SH) - Sorry, can't speak to future products, but think that the option of offering uncompressed 4:2:2 is an important first step in placing the D4 in a professional filmmaking environment. This is an option not offered in any other HDSLR.
Can the D4 be powered by an external battery source, like AntonBauer or V-mount?
(SH) - You'd have to adapt it somehow, and we don't make a provision for that, so you'd have to ask those battery manufacturers. (We do provide an AC power supply that someone could probably hack something up around. - But that'd of course be an "unsupported" usage. :-)
The D4's HDMI is 4:2:2 8bit as stated by Nikon, -but what does "uncompressed" mean? Exactly how is 1080P output via HDMI port?
Uncompressed means that you're not using the in-camera H.264 compression, instead allowing the external device to record in the desired or supported format for editing. In order to get full 1080p output from the HDMI port for external recording, both memory cards must be removed from the camera. That's what triggers the full 1080p output from the HDMI port for recording. When recording to either of the two memory cards, the HDMI output for monitoring is only for monitoring purposes, not suitable for recording.