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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

4K HD and 4K 16:9 difference

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PabloMCV

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Hello

Can you explain what is the difference between 4K HD and 4K 16:9

Sorry I don´t understan

Thanks

Pablo
 
One is 4096 x 2160 and the other is 3840 x 2160.
 
"4K" is no longer 16:9, 4K HD is. There used to be (RED ONE) both 4K HD and 4K 16:9 resolutions available. The difference was 4K HD was evenly divisible by 1920x1080 which made transcoding faster but both were 16:9 formats. Now on the Epic/Scarlet cameras 4K is 4096x2160 and has an aspect ratio slightly wider than 16:9, effectively 256:135. The 5k, 3k and 2k resolutions are also 256:135. To scale and fit height to say 1920x1080 you will crop information from the sides.

Does anyone know why there doesn't seem to be 2/3/4/5k resolutions that are 16:9 on the newer cameras?
 
4K: 4096x2160 (a.k.a. 2160p)
Aspect Ratio: 1.9:1
Used in cinema.

4K HD: 3840x2160 (a.k.a. Quad HD)
Aspect Ratio: 16/9 (1.78:1)
Used when the delivery format will be 1080p. 4K HD (QHD) is exactly four times larger than 1080p, so it resizes proportionally down to 1920x1080.
 
PabloMCV said:
Hello

Can you explain what is the difference between 4K HD and 4K 16:9
Click to expand...

A little history:

4K 16:9 was the original 16:9 resolution offered in the Red One. It is 4096x2304. It is not, at present, available in Epic/Scarlet. (I have no idea if it ever will be.)

4K HD is 3840 x 2160. It was developed to provide a setting that is sharper and less processor-intensive for downsampling to 1920 x 1080 HD. It is, as Brian says, "Quad HD" or exactly 2x the resolution of 1080HD in each dimension, so the math is simpler for the downconverter, resulting in better, faster downsampling (especially in programs like FCP that are not the best down-samplers on the planet). This resolution is available in Epic/Scarlet.
 
Brian Iannone said:
4K: 4096x2160 (a.k.a. 2160p)
Aspect Ratio: 1.9:1
Used in cinema.

4K HD: 3840x2160 (a.k.a. Quad HD)
Aspect Ratio: 16/9 (1.78:1)
Used when the delivery format will be 1080p. 4K HD (QHD) is exactly four times larger than 1080p, so it resizes proportionally down to 1920x1080.
Click to expand...

Correct ...
 
I suppose they dropped it for other sizes since for a delivery in HD 1080 it doesn't make much sense to use anything else but Quad HD.
You might say that you'd like 5K 16:9 for getting a bit wider from the same lens, but that's about all I can see as useful. In most other cases you'd shoot for multiple delivery formats anyway and would need to frame accordingly. BTW, 5K is great for re-framing in post, but then your original ratio doesn't matter that much.
 
Think of what happens to individual pixels when you scale down. In 4K HD a four pixel square is combined into one final pixel. This is not true of the other formats: when combining the 'edge' pixels have to be handled in terms of percentages. Think of 3K HD where 1.5 pixels in each direction get combined into one pixel. 5K HD is much more complex.

If final delivery is 1080p I think I'd shoot 4K HD, unless I needed a wider shot than my widest lens could deliver.

Bob
 
Chris McKechnie said:
So if you're wanting to acquire in 5k but have a 1080p deliverable, what would be the ideal aspect ratio to not lose too much of what you're seeing on the monitor when recording?
Click to expand...

Personally like 5K WS as that is 5120 x 2160 pixels which means I can crop to 3840 x 2160 for Quad HD or crop to 3840 x 2160 and scale 2:1 for 1080p HD, or scale 5:4 for 4096 x 1728 (DCI Scope) or crop to 4096 x 2160 or 3996 x 2160 (DCI Flat) and still have some room to reframe for 3D...and I can still record as high as 120 fps ...
 
Seems people missed the OP's exact question. 4K 16:9 is *NOT* 4096x2160, it's actually 4096x2304 and is a 16:9 aspect ratio.

RED One "4K" modes are as follows:

4.5K = 4480x1920 | 2.33:1
4K 16:9 = 4096x2304 | 16:9
4KHD = 3840x2160 | 16:9 (this is commonly known as quad-HD or 4xHD 1080p)
4K2:1 = 4096x2048 | 2:1

The differences between 4K 16:9 and 4KHD are that the 4K 16:9 frame is actually "4K" in that it's 4096 pixels across. Being slightly larger, it is closer in size to the full Super35 frame, but not by much -- it's very close to 35mm Academy format. The 4KHD mode has some advantages as it provides quicker scaling to 1080p HD since it is even 2X scale in both linear directions or a total of 4 times the number of pixels.
 
Stuart English said:
Personally like 5K WS as that is 5120 x 2160 pixels which means I can crop to 3840 x 2160 for Quad HD or crop to 3840 x 2160 and scale 2:1 for 1080p HD, or scale 5:4 for 4096 x 1728 (DCI Scope) or crop to 4096 x 2160 or 3996 x 2160 (DCI Flat) and still have some room to reframe for 3D...and I can still record as high as 120 fps ...
Click to expand...
+1 5K WS seems to provide the most delivery options for the buck and the simplest 5K workflow.

for 1080P delivery... it should also be noted that 4K HD transcodes much faster than 4K 16:9 - because the math is perfect - no rounding. either and faster with our without Red Rocket
 
Uli Plank said:
I suppose they dropped it for other sizes since for a delivery in HD 1080 it doesn't make much sense to use anything else but Quad HD.
You might say that you'd like 5K 16:9 for getting a bit wider from the same lens, but that's about all I can see as useful. In most other cases you'd shoot for multiple delivery formats anyway and would need to frame accordingly. BTW, 5K is great for re-framing in post, but then your original ratio doesn't matter that much.
Click to expand...

It does make sense - it gives you a field of view that is much closer to standard academy.
 
Bob Gruen said:
Think of what happens to individual pixels when you scale down. In 4K HD a four pixel square is combined into one final pixel. This is not true of the other formats: when combining the 'edge' pixels have to be handled in terms of percentages. Think of 3K HD where 1.5 pixels in each direction get combined into one pixel. 5K HD is much more complex.

If final delivery is 1080p I think I'd shoot 4K HD, unless I needed a wider shot than my widest lens could deliver.

Bob
Click to expand...

This is terrible advice.
 
Steve Sherrick said:
Which part are you saying is terrible advice?
Click to expand...

It is advice that is from the Brute Force Academy of Cinematography.

A wider field of view will look different if filmed by a 35mm lens at 5K than it will from a 24 mm lens at 4K. Not just sharper, but different focus falloff, not to mention signal to noise on final image is much higher at 5K - you are using more light to create your image. AT 4K you are zooming in on noise, however nominal that noise may be on MX. Also, side-by-side, even on Red One, 4K 16:9 looks creamier and less digital than 4KHD.

This kind of simplistic, vaguely brutalist advice bugs me - it's like when people say "just adjust your iris if you want less light".

There is more to all this than counting pixels...
 
Jeff Kilgroe said:
Seems people missed the OP's exact question. 4K 16:9 is *NOT* 4096x2160, it's actually 4096x2304 and is a 16:9 aspect ratio.

RED One "4K" modes are as follows:

4.5K = 4480x1920 | 2.33:1
4K 16:9 = 4096x2304 | 16:9
4KHD = 3840x2160 | 16:9 (this is commonly known as quad-HD or 4xHD 1080p)
4K2:1 = 4096x2048 | 2:1

The differences between 4K 16:9 and 4KHD are that the 4K 16:9 frame is actually "4K" in that it's 4096 pixels across. Being slightly larger, it is closer in size to the full Super35 frame, but not by much -- it's very close to 35mm Academy format. The 4KHD mode has some advantages as it provides quicker scaling to 1080p HD since it is even 2X scale in both linear directions or a total of 4 times the number of pixels.
Click to expand...

Thank you Jeff! A buddy of mine needed to know what aspect ratio matched 4096 x 2160 on the RED One... your post gave me the closest aspect ratio.
 
Seriously though, if there's no realistic route to a piece being seen theatrically, then it will live its life as a piece of 1080P rec709 media (at best) destined for compression to less than 8mb/s in MPEG-2. For that pathway I think the slightly crunchier edges in the "brute force" full integer downscale might actually provide more usable metrics for the encoder's algorithms. If so, that would typically (some high contrast or extreme exposure samples excepted) improve the IQ of the encoded media the viewer will see.

On the flip side, for any narrative or "glossy" piece that lends itself to a creamier look I'd shoot the biggest frame I can (love that 5,120 by 2,700 on the Epic) with a 16x9 guide for reference and manage the scaling filter type, contrast distribution, saturation, curves and other values during grading to reveal as much or as little of the true resolution of the base image as suits creative intent/cosmetic imperatives/etc.

Cheers - #19
 
Rob Ruffo said:
It is advice that is from the Brute Force Academy of Cinematography.

A wider field of view will look different if filmed by a 35mm lens at 5K than it will from a 24 mm lens at 4K. Not just sharper, but different focus falloff, not to mention signal to noise on final image is much higher at 5K - you are using more light to create your image. AT 4K you are zooming in on noise, however nominal that noise may be on MX. Also, side-by-side, even on Red One, 4K 16:9 looks creamier and less digital than 4KHD.

This kind of simplistic, vaguely brutalist advice bugs me - it's like when people say "just adjust your iris if you want less light".

There is more to all this than counting pixels...
Click to expand...


Simplistic? I believe I stated exactly why 4KHD came to be, it's benefits, and pointed out that I could also get that little bit of extra width if I were up against a wall and needed it.

Brutalist? Are you serious? What planet are you from where switching between 4K 16:9 to 4KHD is some kind of violent behavior?

I hardly think that a few wide 4K shots are going to jump out of a film that is otherwise 4KHD. As someone who is focused on the entire production process (pre-prod, prod, and post) I stand by my advice. Not everyone has a RedRocket card and all the wonderful support hardware in their workstation, and there is a significant difference between the two when editing and rendering.

There are reasons that Red created the 4KHD format. One is the math gets easier for the computer and oh, BTW: it's more accurate too. Scaleing in any other fashion creates "creamyness" or as others would call it "softness" due to pixels being unevenly divided and added to each other.. If you want softness you can add it in post easy enough (oh dear!). I have yet to see a sharpening algorithm that actually worked.

Hey Rob, I actually have 4K 2:1, 3K 2:1 and (horrors!) 2K 2:1 in the same film!!! I had to because I needed slow motion... Had to do it. Guess it's not worth watching... Too brutal...

Sheesh...

Bob
 
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