Most people believe that 2160p and 4K as interchangeable terms. However, they’re actually slightly different. True 4K Ultra High Definition (UHD), also known as DCI (Cinematic) UHD, uses the full 4096 x 2160 pixel resolution. In contrast, 2160p UHD cuts off a little short resolution-wise.
To be more specific, 2160p only measures 3840 x 2160 pixels. That’s 3,840 pixels horizontally and 2,160 pixels vertically. When you round it off, its 3,840 pixels is technically 4K. However, in terms of raw pixel count, it’s about 160 pixels short of 4,000 pixels or 256 pixels short of 4,096.
Further reading: 1440p vs. 4K: Is 1440p better than 4K?
With that said, in regards to 2160p vs 4k – Why is it called 4K instead of 2160p? Keep on reading to find out.
Comparison Chart
Let’s compare 2160p and 4K. They’re technically the same, but for comparison’s sake, 2160p here refers to rounded-off 4K (3840 x 2160 pixels) and 4K refers to true DCI 4K (3840 x 2160 pixels).
| Categories | DCI 4K (4096 x 2160) | 2160p (3840 x 2160) |
| Also Known As | Ultra High Definition or DCI 4K UHD | Ultra High Definition or 4K UHD |
| Pixel Count | 4096 x 2160 pixels (DCI 4K UHD) | 3840 x 2160 pixels (4K UHD) |
| Comparison | 4K has twice the resolution of FHD or 1080p. It measures 8MP (megapixels) compared to FHD’s 2MP size. 4K UHD distinguishes itself from 8K UHD (which measures 7680 x 4320 pixels) by being more available among projectors and HDTVs. The full 4K DCI UHD isn’t as readily available in projectors compared to its 2160p counterpart. These resolutions both use progressive scan since interlaced or alternating scanning is a relic of the past for analog video. | Projectors presently can only go up to 3840 x 2160 4K resolution. Some people might confuse DCI 4K and 4K. As a rule of thumb though, DCI 4K is about as rare as 8K. Most video is instead upscaled to 2160p or 3840 x 2160 pixels. Technically, 4K UHD in projectors is rounded off and is actually 3840 x 2160 pixels. DCI 4K offers the full 4096 x 2160 pixels. It can also reach up to 8MP despite having a shorter row or horizontal size compared to DCI 4K. |
| Display Type | It’s becoming more and more common for huge HDTVs and the latest projectors from the late 2010s to the early 2020s. Digital cameras are likelier to have more affordable DCI 4K compared to projectors and HDTVs. The 2160p resolution is the more common 4K compared to DCI 4K resolution. | It’s basically the 720p HD equivalent of 4K for HDTVs. True 4K or DCI 4K is a major selling point for HDTVs. 2160p is the de facto standard for projector-level 4K at the time of this writing. True 4K DCI UHD is also available for projectors but at a much higher price point. |
Why is it called 4K instead of 2160p?
The reason why 4K UHD is called 4K instead of 2160p is because it wishes to differentiate true Ultra HD compared to “fake” or “slightly smaller” Ultra HD. 4K or DCI 4K refers to the resolution measuring 4096 x 2160 pixels.
2160p 4K, despite sharing the 4K appellation and 2,160 pixels vertical dimension, refers to the much smaller resolution measuring 3840 x 2160 pixels. 4K projectors are likelier to have this measurement instead of true 4K or DCI 4K.
In terms of display types, true DCI 4K is more available in digital cameras than HDTVs and projectors. Those extra pixels of horizontal real estate is a major selling point for HDTVs and projectors though, but at an extra high price point.
It’s easier to go DCI 4K on a still digital camera compared to uncompressed full motion video. Those extra pixels make all the difference in terms of quality and expensiveness.
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Similarities and Differences of 4K and 2160p
The difference between the two isn’t that drastic. One is just a couple of hundred pixels wider compared to the other.
They’re both capable of doing High Dynamic Range (HDR) and Wide Color Gamut (WCG) display technology, which results in sharper images and wider color variegation when push comes to shove.
So is the only real difference between 2160p and (DCI) 4K is a matter of a few extra pixels horizontally? Yeah, basically. Knowing this will definitely help you discern whether a projector or HDTV is being truthful when they claim their display is true Ultra HD or it falls a little short of 4K.
Even though 2160p and 4K has the same height, 4K is 256 pixels wider compared to 2160p. This ratio of 4K was developed by the Digital Cinema Initiative. This is the reason why 4096 x 2160 is referred to as DCI 4K or C4K (Cinema 4K).
What Does this Mean for You?
When you’re viewing 4K films at cinemas, they’re most likely using projectors that are DCI 4K instead of the slightly inferior and shorter 2160p UHD. It’s more common for people to care about true 4K in still cameras, such as the DCI 4K available in Panasonic Lumix GH5 or Sony FS7.
Naturally, true 4K projectors are available from Sony, specifically its SRX-R815P model with the DCI specification. If you’re going to buy a 4K DCI HDTV though, make sure you pay more attention to screen size in inches than pixels since those pixels count the most on larger screens.
The main thing to keep in mind with DCI is the forward march of technology. While UHD (and even 1080p FHD) is the current standard for HDTVs and projectors, it’s still the older technology. If you wish to future-proof your work, going the DCI route might be best in future purchases.
Videos
Here are some YouTube videos discussing the difference between 2160p and 4K.
- DSLR Video Shooter, “The Difference Between C4K and UHD“, YouTube.com, July 8, 2015
- ChungDHA, “4K DCI vs 4K UHD Explained“, YouTube.com, September 24, 2020
Concluding Thoughts
Comparing 2160p as the 4K version of 720p HD while DCI 4K serves as the 4K version of 1080p Full HD is an oversimplification. 2160p only falls short slightly compared to 4K. 720p is smaller vertically and horizontally to its 1080p Full HD counterpart.
Aside from smaller screen real estate, they’re basically the same 4K. They can both accommodate HDR and WCG. They work best with highly large, uncompressed video running at 60FPS to 120FPS or more. 4K DCI isn’t so much larger that it’s a rare video format compared to 8K or 10K either.
References:
- “Is a 2160p TV worth the upgrade from 1080p? Is it really a noticeable difference in quality for movies and gaming?“, Quora.com, April 8, 2017
- Liza Brown, “4K VS 1080P: Why 4K is Better than 1080P“, Fimora.Wondershare.com, March 24, 2021
- “Technical Jargon Explained: What’s the Difference Between 4K UHD & 4K DCI?“, HireaCamera.com, January 11, 2018