You may have heard the term “4K” when doing some research on video production, but do you actually understand what it means? While it is not necessary for your video, it does offer benefits as well as a few drawbacks that are worth considering.
First off, what the heck does 4K mean? 4K, also known as Ultra High Definition, or UHD, refers to the resolution of the image, almost 4,000 pixels (3840x2160). For reference, 1080p, also known as Full High Definition or HD, is 1920×1080. 4K has a higher resolution than 1080p, and therefore produces a more defined, higher quality image. It essentially comes down to the details of the image when viewing up close.
Besides the image quality, there are benefits on the post-production side when working with 4K footage. More than likely, your video will not be viewed at 4K. Online playback will generally be at either 720p or 1080p. However, there are benefits of working with 4K footage in a 1080p sequence.
The benefits of working with 4K footage in a 1080 sequence revolve mostly around reframing the shot. Because you now have “more” material to work with than what will be seen, you are able to zoom in, or scale up, on a shot (to a certain degree) without sacrificing quality. Being able to reframe the shot gives the affect of different angles. For example, you can shoot an interview with one camera in 4K and in the edit, you can create a second camera angle by “punching in” for a pseudo close-up. While this won’t give you a true second camera angle, it is a solution when editing a one-camera interview. Other benefits include the ability to create camera moves, stabilize footage, and better position graphics.
You now may be thinking, “Wow, this all sounds great! Why not shoot everything in 4K?” There are some drawbacks to keep in mind. Most of the disadvantages revolve around time and money.
Hunter Kallenbach, Motion Source senior editor, offered his insight:
“The process of working with 4K footage is time consuming. A 4K file is 4 times the size of a 1080 HD file. This means transcoding the footage and ingesting it into an editing program is a longer process. From a client end, this means more editing hours will accrue. Some computer systems can not handle 4K well. This can cause stuttering in playback, loss of image quality in the viewer, and potentially crash your whole system. If your video is going to stream online, 4K is usually not an available option. Shooting in 4K also takes up a lot a space. This means you will need a large hard drive to store the project which could, again, lead to additional costs.”
Craig Bass, Motion Source creative director, provided his opinion and goes into more detail on the technical and aesthetic disadvantages:
“4K, in the majority of applications, is only useful for practical reasons, like those that you have listed above. As stated by Stu Maschwitz, in an article dated from way back in 2013, ‘If you bought a 60” television, you’d have to sit about four feet away from it before you’d perceive the full benefit of 4K over good old 1080p.’ (https://prolost.com/blog/2013/1/22/4k-in-the-home.html). To my line of thinking, this says it all. For most applications, 4K is entirely useless in terms of perceptual improvement of the image. In most client applications--video for the web, or even for television broadcast--it is entirely extraneous.
Apart from this, 4K is extremely resource intensive. Due to the amount of data that is recorded when filming in 4K, working with it can be somewhat laborious. For one thing, the media that you record onto is going to fill up much faster due to larger file sizes. Depending on the amount of cards (media) that you have on set, this can necessitate transferring the footage over to a computer or hard drive, so as to free up cards for further filming. This can be unideal for two reasons: 1.) it takes time out of the shooting schedule for a footage dump; and 2.) you will then be overwriting cards, meaning that if, by some horrible twist of fate, the computer and/or hard drive(s) that you are transferring to have issues, you no longer have the original media to pull from. I have never experienced this potential tragedy, but that does not preclude it as a possibility.
The increased data rate can also makes post-production a bit of a headache. 4K files, due to their sheer size, require relatively powerful computer processors to play in real-time. If your processor is not up to the task, the video itself will either freeze, or stutter, when playing back. One way to deal with this is to create proxy files--lower resolution copies--that are utilized while editing, and only replaced with the original files once the cut has been locked. As you can imagine, this increases the amount of time required during post-production.
Up until this point, all of the arguments that I have made for avoiding 4K if possible have been from a purely pragmatic perspective--let's get into aesthetics. Many people extol the value of 4K in, essentially, providing you with two shots in one. The idea is that, if the footage is going to be released at a lower resolution--for instance, traditional 1080 HD--it can easily be scaled up without losing quality. If we look at the 1080 HD frame as a postage stamp, 4K would be a notecard. To fit the 4K image into the 1080 frame it must be scaled down--again, think of the postage stamp to notecard size differential. But, what if you were to leave the notecard at its current size, and view it through the window of the postage stamp? Well, whatever portion was fit within the frame would be at full 1080 resolution, and you could therefore take a single shot and cut it up into a variety of shots via resizing the image. Right? Not so fast. While this is technically true, there are two major issues here. The first issue is that the apparent sharpness of a lens works in conjunction with the size of the image that it is intended to display. What may look razor sharp at its full size, may not appear anywhere near as sharp once you hone in on a certain portion of it, regardless of the increased resolution that 4K offers. This means that, while 4K should technically allow for you to scale an image up to 200% while retaining full resolution, the result is often anything but sharp and clear. Instead, you are generally confined to increasing the size of the image approximately 25% before you begin to compromise apparent sharpness--a far cry from the 'technically' promised 200%.
Apart from this, you must keep in mind that filmmakers select different lenses for different effects. This means that when a shot in a piece goes from, say, wide to close; there are certain visual markers that should change with perspective: field of view, shallowness of the focus, etc. If one were to use 4K to simply pull a close-up from a wide shot, these changes of perspective will not occur, and can leave the audience subtly feeling like something isn't quite right. The correct way to capture a sequence of shots like this would be to change the lens and or physically move the camera--depending on an increased resolution to do this for you in post is, frankly, lazy.”
Final thoughts: Don’t assume your video needs to be shot in 4K because it’s “bigger” and “better”. Consult your production team to discuss and determine how your video should be shot. While 4K isn’t going anywhere (cameras have already moved on to 8K capability), consider the time and cost compared to the benefits. Most times, “good old 1080p” will do the trick.