Author Topic: Acer XF240H Review & Viewsonic XG2402 Review: 144hz 1080p Matte TN Panels with AMD-Free-Sync  (Read 7948 times)

NCX

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Inspecting The Wounded
« on: August 10, 2018, 02:03:10 am »
Preset Color Accuracy

DSC_0031 by Deepinthesky Teslastorm, on Flickr

Both monitors suffer from contrast, gamma and black uniformity loss at 144hz versus 60hz, and both monitors need to use different gamma settings to raise the gamma at 144hz to prevent them from looking washed out.  I also tested two inputs for each monitor, those being Displayport (assuming PC use @144hz) and HDMI (assuming console use @60hz).  The Acer's preset color accuracy is slightly different while the Viewsonic's Displayport and HDMI offer the same preset color accuracy.

In all HCFR colorimeter measurement comparisons below the following applies:

Top Left=Acer XF240H 60hz Default                                                                      Bottom Left=Viewsonic XG2402 60hz Default
Middle Top=Acer XF240H 144hz Default                                                                Middle Bottom=Viewsonic XG2402 144hz Default
Top Right=Acer XF240H 144hz with Gamma setting fix                                         Bottom Right=Viewsonid XG2402 Gamma and RGB Level Fix

The Acer XF240H is cable of providing accurate results at 144hz when the Gamma setting is changed from 2.2 to 2.4, and the Black Level setting is changed from 5 to 4.

The Viewsonic XG2402 is capable of providing accurate results by switching the color temperature to User and the ViewMode to Text.

I try to get display gamma to match closest to whichever standard they're preset closest to, which is usually either sRGB (non-linear gamma) or HDTV/REC 709 (linear 2.2 gamma).  The Acer comes closer to HDTV while the Viewsonic is closer to matching sRGB gamma.
 
HCFR Grey Scale Delta E Averages
Spoiler (hover to show)

At 60hz the average color error (Delta E) of both monitors is higher than at 144hz, and the RGB balance is also different.  The Acer is more accurate without changing any settings, however its gamma is significantly worse at 144hz since gamma averages at 1.74 which is very low and results in a very washed out image.  The XG2402 is a bit better with its 2.02 gamma average, but its gamma curved is skewed which results in dark colors and greys looking washed out, bright colors and greys to be to dark.

HCFR Gamma Measurements
Spoiler (hover to show)

As expected, both monitors suffer from gamma drops the higher the refresh rate goes above 60hz.  At 60hz the Viewsonic offers a non-linear gamma curve similar to that of the sRGB standard while the Acer's gamma is more linear, but too high resulting in a bit of black crush, as well as makes bright grey and some bright colors become slightly to dark, but not as dark as the Viewsonic.

As mentioned above, at 144hz the Viewsonic easily bests the Acer's gamma which is far too low, though both monitors look washed out and dull.  Changing two different settings on both monitors provides the best results both are capable of, however the Acer is clearly superior since its gamma is more linear and its two gamma settings allow for more precise adjustment. 

The only way to prevent dark greys and some colors from being washed on the XG2402 is to also put up with 20-100% white (medium to bright greys and colors) being too dark, dulled, and to deal with a bit of detail loss do to the darkening and blending of colors and grey shades.  The XF240H's gamma remains slightly U-Shaped, but it can be raised and lowered according to preference.  10% white (dark grey) at 2.3 is slightly too high, but lowering the gamma causes 30-70% white to drop to 2.0, which results in some colors and shades to be obviously washed out.

HCFR RGB Measurements
Spoiler (hover to show)

The XG2402's RGB Levels are poor, quite skewed and require calibration with a colorimeter and an ICC profile to fix while the Acer is a bit more accurate since the RGB levels are more balanced and linear.  I was unable to improve either monitor significantly by adjusting their Red, Green and Blue settings in the menu, and had to rely on the ICC profile created by dispcalgui program and my Spectracal C6 HDR2000 colorimeter.   

HCFR Color Temperature Measurements
Spoiler (hover to show)

HCFR Color Space Measurements
Spoiler (hover to show)

The XG2402 can fully cover both the sRGB and HDTV/REC 709 color space, and only slightly over-saturates greens, yellows and oranges while the Acer XF240H falls short in the top left (dark blues and greens) and over-extends significantly more on the right side of the triangle.  Since the over and under-saturation differences are slight the difference between the two monitors is slim, and calibration is required to take advantage of the Viewsonic's superior color space coverage since the preset gamma is so skewed and makes light colors and greys to dark and dulled.

Standard and Custom 1 Measurements by colorimeter owning forum member MagicalChicken.  His XG2402 was significantly more accurate than the unit I tested, but has very similar gamma and RGB.


The Acer XF240H offers great preset color accuracy at 60hz which I can't really criticize when considering the low price.  The Acer is very accurate and free from an obvious preset color dominance while the Viewsonic XG2402 is too blue and has both skewed and inaccurate gamma and RGB levels which can not be normalized without an ICC profile.  When switched to 144hz the Acer suffers from a significant gamma drop and looks significantly more washed out than the XG2402, but the RGB color balance remains vastly superior, and it's possible to achieve mostly accurate gamma from the Acer at 144hz by changing the Black Level setting from 5 to 3, and gamma from 2.2 to 2.4.  The XG2402 also requires two different settings to be changed, those being the Black Stabilization setting from 11 to 9, and Gamma setting from 2.2 to 2.4.

Regardless of which settings are used the Viewsonic's gamma is way too high in the 50-100% white section resulting in many light colors and shades to be too dark and a bit dull while dark colors and shades are a bit washed out.  The Acer's gamma is more linear, and way too low at 144hz, but significantly superior after changing the Black Level and Gamma settings.  The Acer also barely benefits from an ICC profile while the Viewsonic needs one to offer good results for a TN panel.

Banding

AUO TN panels tend to suffer from very obvious and frankly horrific banding when viewing this Dawn Engine image and this 60fps Westworld trailer.  Here's the Dell S2417DG/S2716DG banding example from a reddit user, and here's the Westworld banding example (top screen).  The post with the Westworld example was not made until long after I sent both monitors back, but I did try the Dawn Engine image on the Viewsonic XG2402 which suffered from the same horrific banding as the Dells.  It's safe to assume that the Acer XF240H also suffers from the same banding since both use TN panels made by AUO.  Both monitors suffered from obvious banding in mostly black filled content or very dark scenes, especially when viewing content on YouTube.  I did not notice banding in any of the dark game (Destiny, Dying Light, The Order 1886) screen shots I display on every monitor I test, or in the games I tried, but there's no denying that banding is a very obvious issue when viewing specific types of content, and is probably going to remain an unavoidable issue among AUO TN panels for some time.  Calibration did not help reduce the banding.

I also checked for banding on my Acer G257HU (1440p IPS), custom glossy 27" 1440p (IPS), Dell S2719DGF (1440p TN),  HP 25es (1080p IPS), Qnix UHD32R (4K AHVA), X-Star DP2710 (1440p PLS) and Viewsonic VP2780-4K (4K IPS).  Only the custom glossy 27" 1440p (IPS) suffered from noticeable banding (increased banding with the ICC profile active) while the rest suffered negligible amounts unless I stretch the 1440p Dawn Engine image out and look closely at what appears to be a sun glint at the center of the crescent arc or moon.

Reddit Posts with banding:
https://www.reddit.com/r/Monitors/comments/9jjcio/24_1080p_144hz_gaming_monitor_without_colorbanding/
https://www.reddit.com/r/Monitors/comments/95t20w/dell_s2417dg_s2716dg_owners_is_color_banding/
« Last Edit: January 29, 2019, 02:07:48 am by NCX »