One of the first things you will note when you search and download stock footage is that the clips come in different image definitions.
Most stock footage agencies organize their libraries, and usually their prices too, according to video resolution, and they all detail the available image quality formats for each clip they offer. The typical resolutions available at most of them are SD (Standard Definition), HD (High Definition) which has variants, and the Ultra HD that is known as 4K and 4K+ (getting to 6K and sometimes even 8K).
If you're not very savvy in technical aspects, you might wonder what's the difference in this image definition specifics, other than the obvious that the higher the definition, the better the image. Which video resolution is more suitable for certain usages? Which is the most versatile? Which resolution makes more sense using in your projects? Here we will answer those questions.
Image Definition Explained
Before we dive in to each resolution quality available in the stock footage market, it's worth to clarify how image definition is calculated.
Of course, you know the quality scale goes from less defined and detailed, to sharper and livelier quality, but how is that determinated? Well, it's all in the pixels.
The more pixels the camera captures, the more detail the image will have. More details make the human eye perceive a sharper image. But when you're downloading and using footage, you will come across different technical terms referred to image definition. And they are:
This refers to the number of pixels displayed in the video, width by height. For example, when you see “1920 x 1080” in a video description, you can know it's saying the image is 1920 pixels wide, and 1080 pixels tall. In general lines, the quantity of pixels displayed by height (or vertically) are the ones used to point the video's definition, so in our example this would be expressed simply as “1080”. As you likely can guess, the higher the number of height pixels, the better the image quality.
It points the proportional relation between the width and the height in the image. For example, a 16:9 aspect ratio means that for every 16 inches wide, the image must be 9 inches tall. Often times, you will find the aspect ratio expressed dividing width by height – in our example, 16:9 would be expressed as “1.77”. The aspect ratio tends to be wider than taller as the definition is sharper. You can easily notice this just by looking at TVs and monitors: the latest and most advanced screens are wider and less tall, whereas old models are more square-ish.
Interlaced or Progressive
Beside the number of vertical pixels (informing of the definition of the image) you can also find a letter “p” or “i” next to the number. This letter refers to the method in which the video has been recorded (and displayed). Some cameras use a system of “interlacing”, capturing and displaying images by alternating lines of video resolution, separated in odds and evens, but scanned so fast that the human eye perceives the image as complete at all times. Other devices record video one line of pixels after the other, sequentially and without alternating, which is known as “progressive” scanning. So if you see “1080p” or “1080i” you know it refers to the scanning being progressive or interlaced. Progressive method delivers a better resolution in general, as the motion appears more fluid.
Storage and Bandwidth
Another basic concept is regarding to how much space the footage files occupy, and how much bandwidth they consume to reproduce.
In blunt, it's simply logical: the more details the image contains (the more pixels it has) the larger and heavier the file will be. For example, 1 hour of HD footage is in average an 8GB file. 4K and higher are bigger.
And if you intend to put your content online, you must consider the bandwidth needed to view it. HD videos need an average of 2.1 mps (megabytes per second) to load and play live. 4K needs as much as 100 mps, so most of people supporting it (like Netflix) compress it to roughly 15 mps (downgrading quality as well), which at the moment less than 25% of the end users have. If your video takes too long to load or buffers all the time, you will lose your viewers even if the image resolution is superb. More if you take into consideration that most home connections in North America are limited to around 30GB of data allowance per month.
Now that you have the basics clears, let's have a look at the different resolutions available:
As its name states, this quality status refers to the standard for most of distribution/reproduction channels and screens, like TV and film. In present day this is considered a bit “dated”, since recording and reproducting devices have improved to capture and play higher-than-standard images.
SD usually has a display resolution of 720 x 480, being 480 pixels tall. In North America it's only available interlaced, and tends to have a square-ish aspect ratio, commonly of about 4:3. Generally speaking, SD quality tends to look blurry and much less defined, particularly when compared to HD. While it's still a decent image resolution, it's being more and more surpassed by edge resolution technology.
Here's how you can identify SD reading footage specifications:
- 720 x 480
- 4:3 or 1.33
High Definition (HD)
Also given away by its name, HD offers a high image resolution, particularly compared to SD. Video and film in this quality is been around since many years, and it's popularity scaled up as end-user technology improved to support it. TVs, monitors and cinema screens, as well as broadcasting, online reproduction and projecting technology now support high definition images that modern camcorders (and even newest smartphones) are able to capture.
HD has two definition variants, 720 or 1080 pixels tall, each with its correspondent display resolution. It's available in both progressive and interlaced scanning (sometimes depending solely on the method supported by the reproduction system), but these are classed separately due to the differences in final quality (progressive is superior resolution, interlaced causes blur and the image ends up looking not much different than SD).
Its aspect ratio displays wider than taller on screen, like a rectangle. However, in many cases you are able to modify the aspect ratio, adjusting the image. For example, many HD tv's and dvd players let you switch between “wide screen” (naturally rectangular) and “full screen” (which will show a squarer image in a black background).
HD delivers more details per pixel, and so the image is much sharper, with a much more “real” feeling. Progressive HD is particularly good for sports or other high motion images, as the movement appears smoother and more realistic.
You will identify HD when you read this:
- 720p, 720i, 1080p, 1080i
- 1280 x 720 or 1920 x 1080
- 16:9 (or 1.77), and for motion pictures sometimes 16:8.51 (or 1.85)
Ultra HD (4K and 4K+)
As like in everything else in our times, image quality technology goes nowhere but further. A superior video definition, Ultra HD, has been around for a while, but became stardarized a few years ago, and it's starting to reach the masses.
Ultra HD is popularly known as “4K”, referring to one of the resolutions, that is around 4,000 pixels wide (a significant difference with SD and HD that are denominated by their height pixel count). There's variants in 4K as well as higher versions, up to 8K.
Many TV broadcasters, and cinema projecting companies have adopted this definition already, but 4K-capable viewing devices are not yet massively used. However, it's expected that within the next 10 years, Ultra HD in all its variants will be the new standard, just as HD is the most popular format now.
4K variants depend on industry standards. For film industry, 4K is usually 4096 px wide, and 2160 tall. That's almost 4 times higher display resolution than HD, and it's what it's known as the DCI (Digital Cinema Initiatives) 4K. Its aspect ratio is of around 256: 135.
For TV, the standard 4K (called UHD-1 or UHDTV) is a bit lower, at 3840 x 2160, and keeps the HD aspect ratio of 16:9. Most TV broadcasters, and online media channels like YouTube, have adopted and support this definition.
But technology doesn't stop there. There's cameras capable of producing 6K and up to 8K footage. 8K has an average of 7680 x 4320 display resolution. Imagine how sharp and extremelly realistic those images are compared to HD!
So, this is how you'll recognize Ultra HD:
- 4K: 4096 x 2160, aspect ratio 256:135 (or 1.89) – 3840 x 2160, aspect ratio 16:9 (or 1.77)
- 8K: 7680 x 4320, aspect ratio 16:9 (or 1.77)
- Progressive scanning
Let's Talk File Formats
Here's another important point to consider when buying stock footage and editing it. Most of stock footage agencies sell their clips in MOV or MP4 formats (some have all clips available in either). For SD, they have them in NTSC (the standard for American television) and PAL (for the UK and Europe).
Now, with 4K and higher, some agencies also allow you to download the RAW file. This is the file straight as it comes from the camera, with no edits. Being such a high resolution file, RAW gives you a much wider range of editing possibilities, which is a great advantage to make the footage merge in to your content smoothly.
What Resolution to Use to Meet your Project's Goals
As we said initially, higher resolution footage is always the best choice, because it's more versatile and gives you greater flexibility in edition and in final cut, resolution and format.
If your project is an advertising video for social media or other small web placement, then SD might be ok, as you don't need the super sharp look for something that will be viewed in a small square within a page.
For YouTube, Vimeo or similar, you are better off using 720p HD resolution: HD videos are popular, it's what most viewers prefer, and at 720p it shows a sharp image in most PC and laptop screens. Plus, most users have enough bandwidth allowance for their viewing experience to be optimal. 1080p wouldn't be sharper anyways, because most screens don't support such definition at the moment.
For TV or film content, HD or higher is the way to go. Again, most systems still support SD, but that's something of the past when it comes to consumer trends, and you want to be up to date. Blu-Ray technology also allows to reproduce HD and 4K without degrading quality (although if the screen used is not 4K-capable some of that will be lost anyways), so if you are producing Blu-Ray ready content, this is your best choice as well.
But here's the thing: even if your final product won't be at the highest resolution, it still makes sense to buy the highest resolution available (or the highest you can afford) of the footage clips you want to use.
Why? Because this will give you room to work with editing and versatility to adapt the content to different purposes and placements. If you buy an SD clip (which are the cheapest in the stock footage market), you are stuck with that resolution. If you run a successful social media video and want to expand it for TV or other media, you likely will need to buy a higher resolution version of the clip. Upscaling is possible to a certain level, but it requires skills, software and time that you won't always have at ease.
The other way round makes much more sense: 4K clips give you a great advantage, specially if you get the RAW files. You can edit in different ways (zoom, grade, mask, etc) without losing image quality, and then you can downscale to the best resolution for your intentions, as needed. For example, you could create a promotional video and scale it to 720p for YouTube, but if it goes viral and you want to take it to TV or other media, you will be able to, as you will own the file in a higher definition already.
If you will be sticking to online reproduction, you could go for HD clips, and downscale whenever you need it. This is cheaper than 4K, but you won't get as much editing possibilities with the MOV or MP4 files.
And keep in mind that technology is in constant movement. Ultra HD keeps spreading and more industries are working in building the support for it to reach the masses. Within the next decade you can expect 4K-capable TV screens to be accessible to most homes, and that coding for 4K streaming/playing online improve to need 10mps only, as well as home Internet service to provide such bandwidth allowance to most users.
With that perspective it makes sense to invest, when possible, in the highest resolution.
So now you know. That's how video definition goes, and those are the points you must consider when browsing, buying and using stock footage in your creations.