4K Displays: Is That the Cost or Something Else?

4K-0713By Steven J. Thorburn, PE, LEED-AP
Co-founder, Thorburn Associates

In a word — yes! It is both a cost and a reference to resolution. In the world of film and video, 4K resolution is a picture that has 4096 pixels side-to-side by 2160 pixels top-to-bottom. In the world of flat panel displays, a 4K display or ultra HD has a resolution of 3840×2160 pixels.

So what does all of this mean? It is a reaction to “bigger is better.” Your flat panel TV at home most likely has 1920 pixels side-to-side and 1080 from top-to-bottom. The ratio of 1920 by 1080 is part of the HDTV standard for a display to have an image ratio that is 16 units wide by 9 units tall.

In terms of camera resolution, this would be a 2-megapixel image. A picture or image with this resolution looks great on 30-, 40-, 50-, 60- and 70-inch displays. When we move into 90-inch and larger displays, some people say there is not enough information for a display that large; they say it seems fuzzy.

This discussion about pixels vs. display size is reminiscent of an article we authored on digital cinema a number of years ago when 4K projection was just coming out. As it was then and still is now, it’s all about pixel density. If you do the math, a 45-inch diagonal display is about 40 inches wide and 22 inches tall. That 45-inch display, in HD format has a pixel density of about 50 pixels, or dots per inch (if you are old enough to remember dot matrix printers) side-to-side on the display. If we were to look at a 90-inch diagonal display, it is about 80 inches wide and 45 inches tall and has a pixel density of about 25 pixels or dots per inch. Pixel density and the distance to the display provide you with the clarity factor. If you are so close you can see the display process, that is not good. It is like looking at an image through a screen door.

If we were to look at that same 90-inch display with an ultra HD signal with 3840 pixels across rather than the 1920, then you would be back to looking at about 50 pixels per inch.

So where is this extra information needed? It’s needed anywhere we need images that need to be close to photo realistic, including remote medical diagnostics, map making, CAD/CAM or direct view displays larger than 100 inches. History is a great teacher. This is the same challenge that digital cinema went through: How many pixels do they need to put on the screen to make an image that is good enough, not equal to film, but good enough in the consumer’s view? Digital cinema is stuck at 4K resolution right now, on a 20 to 40 foot if not wider screen. A 4K image on a forty foot screen is about 8 pixels per inch… so it is all about what you want to see: 8 to 16 pixels per inch for the movies, 25 to 50 for TV at your home, or 100 on your laptop. The question is how much information do you want and where?

As to the price, You should be able to get a 4K display at your favorite box store for about $6,000 right now. The price should be down to about $4,000 dollars for the holidays and definitely for the Super Bowl. Ultimately, the questions we always ask is, what are you looking at, what do you need to see, how much resolution is needed to support your computer desktop, or is a life at stake? These are the questions that will help you decide if 4K is needed or if it is just the next wow factor. A 4K image on a screen less than 80 inches just to watch movies or sports… you will have the bragging rights of the neighborhood, but will you see the difference? Most experts would say no.

Steven J. Thorburn, PE, LEED-AP is co-founder of Thorburn Associates, Inc., an acoustics, technology and lighting design firm with offices in California, Florida and North Carolina. He is a recipient of InfoComm’s Educator of the Year award and is active in the design and development of projects around the world.