14 terms you need to know by heart before you buy a 4K Ultra HD Blu Ray
A journey into what really makes 4K Ultra HD colors stand out from the pack
4 February 2019
by Edoardo L'Astorina
So you just got your brand new 4K TV and an Ultra HD Blu Ray player
You’re an avid movie fan. And you just can’t wait to play Blade Runner, Inception, 2001: A Space Odyssey and many, many more outstanding and crisp 4K titles
But how are you going make your 4K UHD Blu Ray collection truly stand out?
How do you know which movies are true 4K and which are a 2K upscale?
And what about HDR? Dolby Vision??
We’re here to help you navigate these waters and learn everything - or close! - there is to know about what makes an outstanding 4K UHD Blu Ray stand apart from the rest of the pack
We are going to start from generic concepts you’ve already heard a million times - like 4K and Ultra HD
Then we’re going to go more specific and explain what HDR, Dolby Vision and Wide Color Gamut are
And for those of you who stick with us to the very end and want to get their hands dirty, we’re going to get into the nitty gritty of 10-bit color and 4:4:4 chroma sampling
Sound exciting? Are you ready to begin our journey?
Here we go!
Let us start our journey with the easiest and most widespread buzzword of our list: 4K
What is it?
4K is a resolution of 4096 x 2160 pixels. As simple as that
It is the resolution that your local movie theater uses in their projectors, and as far as digital goes it is considered the industry standard
You may be wondering:
This is the resolution of my TV, right?
And the answer is… no!
The resolution of your TV - and mine - is actually…
Ultra HD refers to a similar but different resolution: 3840 x 2160 pixels
Whenever your TV, or Netflix, Amazon and a Blu Ray disc advertise themselves as 4K, they are actually Ultra HD
It’s just the format that home video ended up settling for. Still amazing resolution and still 4 times as detailed as HD!
Now that we got the easy part out of the way, let us get more specific and dive into what makes our 4K UHD Blu Rays as amazing as they are
We’re gonna start with explaining the difference between a true 4K source and a 2K upscale
True 4K is also referred to as Native 4K. In the case of a 4K UHD Blu Ray it tells us that the resolution of the source material used for our disc was actually 4K
Maybe the movie was shot with a digital 4K camera. Or maybe it’s a film shot on 35mm and the original film was scanned in 4K and then transferred to our disc
True 4K is by far the method that makes our 4K UHD Blu Rays shine the most and makes full use of our resolution
The results, like 2001: A Space Odyssey and Blade Runner: The Final Cut are stellar
What happens when the source is not 4K?
When the source used for our disc is not 4K then it was a 2K Digital Intermediate. That intermediate was then upscaled to 4K and transferred to disc
Upscale you say? Isn’t that what my player already does?
Yes and no
Let me explain
While it’s true that your 4K UHD Blu Ray player will upscale a 2K picture, the quality of the work carried out by the technicians who are doing the upscale for the release will far outweigh the performance that any player will ever be able to achieve
On top of that, a lot of other features affect picture quality just as much as resolution does
A 2K upscale is still going to benefit from fantastic improvements like HDR and Wide Color Gamut. So while the source resolution is not optimal, a disc like Sicario: Day of the Soldado and Ant-Man and the Wasp is going to look incredible
Let’s get ready to get a little more technical and have a look at those features - okay?
That means High Dynamic Range. HDR is a process that results in a higher contrast between the darkest blacks and the brightest whites of each image
That range in contrast makes pictures feel more life-like to our human eye
4K UHD Blu Rays are all HDR mastered, as are many 4K releases by Netflix and Amazon
But there’s more
There are different kinds of HDR available, and our next sections will focus on the most popular three
HDR10 is the most common form of HDR and is what people really refer to - most of the time! - when they address High Dynamic Range
HDR10 is an open standard and you are going to find it on all 4K UHD Blu Rays, in many Netflix and Amazon releases and on the majority of 4K UHD TVs that are produced
What standards does a disc - or a TV - need to meet to qualify for HDR10?
A color subsampling of 4:2:0, a 10 bit color depth and the REC.2020 color space
You are probably wondering: what do all these mean?
Don’t worry! We cover all those in our sections below
In the meantime, let us take a look at two more HDR types - shall we?
Dolby brought their own name to the game in the form of Dolby Vision HDR - usually referred to as just Dolby Vision - and they did so by enhancing standard HDR10
What did they do?
Dolby added metadata about contrast in every frame and they called it dynamic metadata, as opposed to the static metadata of HDR10 which changes only scene by scene, not frame by frame
The results does offer a better picture quality - although support for Dolby Vision is not as widespread as HDR10
4K UHD Blu Rays that come with Dolby Vision include The Matrix, Star Wars: The Last Jedi and Transformers: The Last Knight
Newer TVs from LG, Panasonic and Sony also support the new format, although maybe not every TV will, as Dolby as decided to make the license for Dolby Vision expensive
And what about Samsung?
For that, let’s talk about the third most popular type of HDR
Samsung just had to do something different to stand out from the pack didn’t they?
Instead of paying Dolby for a Dolby Vision license Samsung developed and released their own HDR based on dynamic metadata - and they called it HDR10+
As opposed to Dolby Vision this is an open format - though Samsung asks manufacturers to pay an annual fee
You are going to find HDR10+ in all flagship Samsung and Philips TVs - and Panasonic recently jumped on the small HDR10+ bandwagon via a simple firmware update
What about content?
Amazon has adopted HDR10+ and the first 4K UHD Blu Rays to sport the format are Bohemian Rhapsody, Alien and Bad Times at El Royal
Now that we have covered HDR - that was an adventure, wasn’t it? - let us take a look at a fundamental aspect that sets some 4K UHD Blu Rays on a whole different scale from others: color
Wide Color Gamut
Wide Color Gamut - also known as WCG - represents all colors you are able to see on 4K UHD and brings the number of colors from the 16.7 million of HD to over 1 billion colors
That is something, right?
On top of that it allows for deeper red, green and blue colors - the core colors knows as RGB - and richer secondary colors like magenta, cyan and yellow
All this makes the colors on screen feel more lifelike and vibrant
You can count on almost every single 4K Ultra HD Blu Ray you are ever going to purchase to sport a Wide Color Gamut
10 bit color
And how do we get to see all those colors?
For that - we are gonna have to get a little more technical. Again. Just for awhile. Warning: Math is involved!
Ready for that?
10 bit color is the range of possible color values per RGB subpixel in each pixel of a 4K UHD panel. There are three RGB sub-pixels per full pixel and each of these subpixels can be 8-bit or 10-bit. 8-bit pixel means 256 shades per color. Either Red, Green or Blue. 10-bit means 1024 shades per RGB color
Now for a little math:
256 x 256 x 256 = 16.7 million
That is what we get on our 8-bit HD panels
And 1024 x 1024 x 1024 = 1.07 billion
Which is what we said in our Wide Color Gamut section. Over 1 billion colors for our 4K Ultra HD pictures
Note: Wide Color Gamut and 10-bit color are sometimes bundled together and referred to as HDR Color
H.265 - also known as Highly Efficient Video Coding and HEVC - is the successor to... You guessed it: H.264 - also known as Advanced Video Coding or AVC
As opposed to its predecessor - which we all enjoyed watching in our beloved HD Blu Rays - H.265 is able to compress video down to a much smaller size. But not just that. H.265 also produces a better picture quality - at the same file size
Sounds amazing right?
The codec is so good that - along with 4K UHD Blu Rays - Netflix and Amazon also use it for their 4K HDR streams - as it allows them to save a lot of precious bandwidth and preserve a strong quality
4:4:4 and 4:2:0
Chroma subsampling is a process by which a few bits of color are removed from the original source
Well, it turns out our human eye perceives changes in brightness a lot more than it does in color, therefore color is where some releases elect to cut corners when they feel like they want to save a little space
Chroma subsampling is a neat trick that allows us to see a compressed image - which takes up less space and is easier to deliver - and make us feel like we are looking at the original thing
4:2:0 is the kind of subsampling we find on HD Blu Rays and all HD content. Also - again for bandwidth reasons - you are going to see it on all 4K HDR Releases by Amazon and Netflix
4:4:4 means no subsampling. Full original chroma. And that is the kind of sampling we find in our 4K UHD Blu Rays
So - did you make it to the end?
In one piece?
And if I ask you how many shades of color there are in each subpixel of a 10-bit color range? Are you able to answer that??
Whether you remember everything or you don't, what matters is that I hope that from now on you are gonna have a better understanding and better tools to choose which 4K UHD Blu Rays are going to make it into your precious collection
And if you ever need a refresher before you make a purchase… Well you can always come here and refer to this guide can't you?