What is the difference between 4K HD and 4K 2:1?

[Stephen Pruitt]

We typically shoot 4K 2:1, but with the newer builds, 4K HD is available. What is the difference between them?

Stephen

[David Didato]

HD is 16:9 ratio, but the resolution is exactly 2x 1920 by 1080. So, its 3840 x 2160. This allows you to use the _H proxies and have a precisely 1080p timeline without scaling, plus it is supposed to render out more quickly to HD. Resolution equivalent to 8.294 Megapixels

2:1 is 4096 x 2048. 8.388 Megapixels.

I usually shoot everything in 16:9 unless I know we will be cutting in with other 1080p footage, when I shoot 4KHD.

4K 16:9 is 9.437 Megapixels, so you "gain" over 1 mp of data.

[Noah Kadner]

4K HD is ideal for projects finishing on TV- such as 1080 or 720p HD because it reduces to 1920x1080 quickly and with no cropping.

-Noah

[Stephen Pruitt]

Well, then we have a redundancy, right?

My camera (Build 17) clearly has three 4K settings:

4K HD

4K 2:1

4K 16x9

So, what's the difference between 4K HD and 4K 16x9?

Stephen

[Stacey Spears]

So, what's the difference between 4K HD and 4K 16x9?

4k HD is 3840x2160.
4k 16x9 is 4096x2304.

[Dominic Jones]

Stacey's dead right, but to expand on it a little, both modes are the same ratio, with 4KHD taking a slight center-crop from the chip to give pixel dimensions that are exactly double 1080p in both directions, yielding an image exactly four times the area.

This makes be-bayering and scaling to 1080p significantly faster, and also slightly higher in quality and therefore better than 4K 16:9 for output that is intended primarily for 1080p distribution - but comes at the loss of a slight bit of FoV from your lenses and the ability to re-frame (whilst keeping said advantages - you obviously still have tons of room to re-frame, but then you lose the speed and quality boosts as you are no longer at exactly 4xHD).

Incidentally, I think it would make more sense for the mode to be called 4xHD rather than 4KHD, but there you go...

Dom.

[Joel Kaye]

4xHD rather t

You're right. That's a better name and represents what it does well. They should change it in the next firmware. They need to add it to RedCine also.

[Ravi Kiran]

How much faster is it to render 4KHD to 1920x1080 on a quad-core Mac Pro?

[James Press]

Ravi, it depends a bit on your setup, but significant enough to shoot 4KHD if your deliverable is 1080. This post is helpful re render times: http://reduser.net/forum/showthread.php?t=24634

[Gavin Greenwalt]

Yeah 4kHD is a bad term considering we already have a term for it: QuadHD (QFHD/QHD).