4K HD Question

[danbrazda]

I know this mode is exactly double 1920x1080 and recommended if you are finishing to 1080P but my question is:

Why? The Red sensor is already 16x9 and using 4K HD is using less of the sensor so why is it better? The only thing I can think of is that the down-convert is easier (ie-faster) because of the math but is the finished 1080P master actually better than a down-converted full sensor image? This mode seems to imply that shooting 4K 16x9 and finishing on 1080P is not the way to go. Can someone explain?

 

[Brandon Fraley]

The only thing I can think of is that the down-convert is easier (ie-faster) because of the math

This seems to be the answer. Easier math means faster decode. I remember reading that it helps against aliasing issue as well, although if true I'm not sure of the exacts circumstances.

 

[Paul Leeming]

Mostly I think an exact 2x downconvert makes the edges much sharper as no funky interpolation is required. We've used it on a few jobs where the client said their final output was 1080p and it seems to be doing the trick nicely.

HTH

Paul

 

[Brandon Fraley]

Mostly I think an exact 2x downconvert makes the edges much sharper as no funky interpolation is required. We've used it on a few jobs where the client said their final output was 1080p and it seems to be doing the trick nicely.

HTH

Paul

are you saying that you noticed "funky interpolation" on your 4K footage converted to 1080?

 

[Paul Leeming]

No, but the overall sharpness just seems a bit more precise when doing an exact 2x downconvert. Don't get me wrong, full 4K images still convert very nicely to 1080p!

 

[Jeff Kilgroe]

Aside from the slightly faster conversions, the H proxies as well as half-res modes out of REDCINE and SCRATCH play natively at 1920x1080. 1080p playback from camera will play at 1920x1080 without cropping the image. So with those last couple output features, this mode makes for a quick means to output 1080p via SDI to something like an HDCAM deck...