Benq Zowie XL2411 gamma/backlight shift

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Tvuce
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Benq Zowie XL2411 gamma/backlight shift

Post by Tvuce » 13 Feb 2017, 18:07

Hi, i recently bought this zowie xl2411 to upgrade my old 60hz led monitor and i'm experiencing this issue.
I really read everywhere on the internet TN panels problems about viewing angles and gamma/color shifts, but i was expecting them to be less eyecatching. I mean, the bottom screen is really brighter than the top and, although it is not really noticeable while viewing colorful images, it's really evident on dark (black) ones.
These are 2 pics i made: http://imgur.com/a/a7jZM
Setting the monitor at 100hz almost eliminates the problem while it is evident at 144hz.
My phone cam makes it seem worse than it is, the pics show my screen brighter than what i see with my eyes. It's still bad tho.
It's really a shame i have to keep this monitor at 100hz to have black uniformity, so i was wondering if it was a normal situation or a bad panel. What do you think?

Sorry for my english and thanks in advance!

Falkentyne
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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Falkentyne » 13 Feb 2017, 18:45

Looks normal. Try standing back from the monitor about 5 meters and take another picture from head alignment. Should look fine.

Tvuce
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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Tvuce » 14 Feb 2017, 09:15

What is causing this effect? It's not gamma shift since it doesn't change if i raise gamma.

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Chief Blur Buster
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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Chief Blur Buster » 14 Feb 2017, 10:56

Higher refresh rates tends to cause reductions in color accuracy, and can amplify gamma shift.

Remember, electronic gamma (picture adjustment) is different than hardware gamma shift (panel limitation). It's like talking about Brightness as an electronic adjustment (histogram / signal curve adjustment) or as a hardware adjustment of backlight brightness. Both are still called "Brightness" but are done completely differently. Likewise, "Gamma adjustment" has nothing to do with "gamma shift" limitations of LCD panels.

Take a look at http://www.lagom.nl/lcd-test/viewing_angle.php ..... at both refresh rates. Do you see worse gamma shift during 144Hz than 100Hz? If so, that's simply the light-polarizing crystal particles in the LCD (Liquid Crystal Display) during faster scanouts, getting less driving electric current per pixel per refresh cycle to maintain orientation. As a result, contrast ratios of higher refresh rates can be lower than the lowest refresh rates, e.g. 800:1 contrast ratio versus 1000:1 contrast ratio. Gamma shift (viewing angle) can actually change on TN panels very slightly during different refresh rates. In this case, the Lagom viewing angle pattern will show more intense gamma shift.

TL;DR: Panels are being pushed to their limits.

Also, another cause you might be seeing is backlight bleed but you said it changes at different refresh rates. If this is extremely objectionable, you could consider a high-refresh-rate IPS or VA, although they may not have the motion clarity/response of TN.
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Tvuce
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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Tvuce » 14 Feb 2017, 11:22

Thank you very much! That's what i was missing in all these days of internet research.
This bright bottom screen bothers me a lot, its really like i bought a cheap gaming monitor while i spent like 250 euros.
After some googling i found these 2 screens looking good color/gamma/input lag wise: Viewsonic XG2401 and Samsung C24FG70.
I know the Viewsonic is always TN panel but it seems to perform better than others and the Samsung having a better panel quality with low input lag for a VA panel.
Both with Freesync and the Samsung has a nice strobing mode. I'm not sure which has better ghosting performance (without strobing ofc).
What would you suggest between these 2?

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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Chief Blur Buster » 14 Feb 2017, 22:10

Of the two models, Viewsonic XG2401 and Samsung C24FG70, I think the Samsung probably has better lower-ghosting picture.

I find that VA panels can have a significantly better picture, higher contrast ratios, but they do have their own separate quirks (greys are a little blotchy during 5-10% grays, different kinds of gamma non-linearities during dark scenes) and it's best to warm up the panel to room temperature for minimum ghosting; they do tend to ghost more when in a cold room.
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Tvuce
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Re: Benq Zowie XL2411 gamma/backlight shift

Post by Tvuce » 15 Feb 2017, 03:03

Damn i'm reading people having the "purple ghosting issue" on samsung c24fg70 even on newest firmwares, but i will probably give it a try.
Just a little thing i can't understand about the c24fg70(probably a noob question): why they mention "1ms(MPRT)" instead of the usual "1ms GTG"?

Edit: ok "MBRT" means Motion Blur Reduction Technology and refers to strobing, so 1ms only refers to strobing enabled. Now i wonder what is GtG response time without MBRT on

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