# 4K Resolution is Blurry and Sharp at the Same Time



## schwine

Television: LG B6 65" 4K UHD HDR OLED
Roku version: Ultra.

I have the above named tv and roku box. 
The 4k tv has been professionally calibrated to provide sharp resolution.

After watching 4k programming on Netflix via Roku Ultra, I notice that 4k resolution is blurry and sharp at the same time. For example, a person in the foreground of program may sharp (extremely sharp) but the background is then extremely blurry. In other scenes of any given 4k tv show, different parts of the screen will be sharp and content around the sharp areas are blurry. The sharp to blurry ratio always varies from scene to scene of any given tv program.

Is this interplay between sharp and blurry images normal for 4k tv? 
I find this effect to be distracting because the tv screen areas that become sharp and blurry are constantly changing frome scene to scene.

Thanks for any tips.


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## cwwozniak

Hi schwine and welcome to TSG.

You are most likely seeing the artifacts of video compression and decompression. It would very large amounts of storage to hold 4K video where every part of every frame is in sharp focus and it would take very large amounts of bandwidth to send that level of quality video at a decent refresh rate.

The video has to be compressed in order to be able to be sent to viewers using broadcast TV, cable boxes, consumer satellite systems, high speed Internet connections, or cell phones. The compression is lossy and the compression algorithms attempt to determine which areas can afford to loose more detail than others. The algorithms also look at differences between each frame and try to only send the changed data with less compression. A fast changing scene will be more blurry than a scene with little motion

You may also be seeing some depth of field limitations of the lens systems of different cameras. A far background will be blurry to some degree when the camera is focused on a actor's face.

FWiW, the compression artifacts on even a Blu-ray disc movie played on a 1080P HDTV annoy the heck out of me.


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## bassfisher6522

schwine said:


> The 4k tv has been professionally calibrated to provide sharp resolution.


By who and how?

I would run through the settings to see for myself what I like and don't like.


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## cwwozniak

schwine said:


> The 4k tv has been professionally calibrated to provide sharp resolution.


If it was done right, the person doing the calibration and adjustments was using professional test equipment to generate high quality test patterns. And those test patterns probably looked very sharp and in focus.

The problem is that the TV can't produce a sharp image if the video source feeding the TV is lacking the detail to be displayed with sharp resolution. The TV cannot reproduce what isn't there.


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## schwine

TV calibration was done by Geek Squad, they seemed to do a good job with that. If the 4k storage provider and the 4k receiver both have fiber optic cables, wouldn't that allow for the efficient transmission of 4k material that is completely uncompressed? My local neighborhood is currently being upgraded to a fiber optic cable network, so I may be able to receive uncompressed video and film on my end at least.


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## cwwozniak

Uncompressed consumer 4K HDTV would require a continuous 4.78 Gigabit-per-second data stream (3840 horizontal pixels x 2160 vertical pixels x 3 primary colors x 8 data bits per primary color level x 24 frames per second refresh rate). The bit rate goes up a bit from there to add two or more audio channels. The data rate for two such streams is within the current hardware limits for fiber optic communications over a single cable but is most likely not practical for any kind of residential service.

Should you wish to continue down this path, the minimum data rate would need to be maintained for the entire data path from reading the hard drives on the source server to the device (if it exists) that converts the stream into the HDMI feed to the TV. Assuming you manage to find a programming provider that stores their content in uncompressed format and would be able to provide you with 4.78 Gigabit-per-second streaming, you would need your fiber service provider to offer a 4.78 Gigabit-per-second data connection to the Internet backbone with no lag. Any bandwidth cap would have to allow for whatever number of hours of TV watching you would wish to do every month. One hour of uncompressed 4K programs would require moving over 2.15 Terabytes of data.


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## bassfisher6522

schwine said:


> My local neighborhood is currently being upgraded to a fiber optic cable network, so I may be able to receive uncompressed video and film on my end at least.


This is the Myth behind fiber optics that has been installed or is being installed in a neighborhood. Fact; you're neighborhood is getting the fiber optic lines installed. Fact; your house is still using copper (coax cable) which is very limited. So unless your house has been fitted or retro fitted for fiber optics you're not going to get the benefits of fiber optics. Point in case; my neighborhood....same deal and my house has coax.

Note: there are some specialty coax cables that can handle said speeds but the cost of that is enormous. My neighbor is a military SAT/COM IT guy.....he's the one that would know.


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