What is up with LightBoost/Turbo240hz and movie squares?

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MonarchX
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What is up with LightBoost/Turbo240hz and movie squares?

Post by MonarchX » 16 Mar 2014, 14:15

My old CCFL HDTV from 2009 with 6ms response time and pretty much all other TVs do a good job at hiding those low-bandwidth/resolution or just general film artifacts that are often represented as squares in dark areas. It happens with full, non-ripped, BD content also. This is a typical example - http://i647.photobucket.com/albums/uu19 ... 9faaf5.jpg but it never happens in games or native 1080p wallpapers. I had that with LightBoost monitor and now with Eizo Foris FG2421. Its not just on my PC - its like that for everyone. My display is calibrated to 100 cd/m^2 with very accurate grayscale white balance and gamma, so calibration is not the issue. I also use madVR advanced dithering, which does help with a lot of content, and yet TVs and I think regular monitors do a much better job at hiding such artifacts. I also cannot apply madVR to Netflix SD content like X-Files...

What are they? I mean I know they are your regular film (especially SD) artifacts, but why are they so visible on light-strobed displays and not-so-visible on regular monitors and TVs? I thought it was the contrast ratio or brightness, but no - Eizo Foris FG2421 has excellent 5000:1 CR. Is it because the screen refreshes so often and light strobing removed the blur effect that hides those artifacts on regular TVs and monitors???

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Chief Blur Buster
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Re: What is up with LightBoost/Turbo240hz and movie squares?

Post by Chief Blur Buster » 16 Mar 2014, 15:51

Those are called compression artifacts.

They become more visible when:
- Contrast ratio is bigger, which means bigger difference between colors
- Player/GPU/etc and configuration (overlay/VMR/etc) uses smaller colorspace
- Your gamma is too bright at the lower end (brighter grays), wider separation between color levels
- LUTs, such as 8bit, 10bit, 12bit. The bigger, the less likely it happens
- Overcompression. BluRay will have far less of these, than Netflix does.
- Better players can help.
- Avoiding NVIDIA Control Panel adjustments can help too (use monitor adjustments instead).
- Multiple low precision LUTs (e.g. video card, monitor, player) can cause rounding errors that reduce number of colors, making these compression squares more visible.

This has been long a problem, especially on highly compressed video on high contrast ratio displays. This happens a lot on plasmas an LED HDTVs too as well, but it can be very display chain dependant, whether these artifacts become more visible or less visible.

The goal of good compression is to make sure the squares are so faint and subtle, they aren't visible.
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MonarchX
Posts: 60
Joined: 23 Feb 2014, 20:07

Re: What is up with LightBoost/Turbo240hz and movie squares?

Post by MonarchX » 16 Mar 2014, 16:46

WIth the latest madVR and high quality 1080p HD content (12Gb+) its hardly an issue, but all 3 of my TVs - one CCFL LCD, another LED LCD, and third is Samsung F5350 plasma end up hiding these artifacts extremely well for HD and SD content. However, LightBoost monitors and Turbo240 show them in their full glory using 100 cd/m^2 white point, which is really a standard minimum for dim environments.

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Re: What is up with LightBoost/Turbo240hz and movie squares?

Post by Chief Blur Buster » 16 Mar 2014, 17:17

If you are using the exact same graphics card (AMD vs NVIDIA) on the same computer on the same display at the same relative field of view (e.g. 1:1 view distance from a display versus screen width), you can isolate banding differences to the display differences.

TN panels have this problem in spades due to their usual 6bit nature, so it should be better on the FG2421 when viewed from the same FOV as a television (more commonly 2:1 ratio of distance versus screen size -- so to treat it on a relative viewing distance, you'd view a 24" monitor from approximately 4 foot away). The contrast ratio is about five to ten times as much, so that may also play a factor. Viewing lagom gradients can determine which adjustments causes banding, so that you can work to minimize them by using certain adjustments and not others. It is wholly possible the FG2421 do not have as good LUTs as your recent televisions. Nearly all gaming monitors are not well optimized for smooth gradients in darks for video. I hope this trend breaks out, with improved gaming monitors in the future.
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