Yes the room is a bit dark

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Well, karavanasam maybe you did the right thing...
Ok sorry for the long posts...
Yeah, first world problems...
Could test 165Hz, and yes it's an improvement over 144 Hz, text scrolling is better.
Included sound system is not great at all for me... But only compared to my previous monitor. If it's your first, maybe you will find it okay.
Was really sceptical but could test Freesync, great, that's what I was looking for. It works really well, what I took for partial ghosting with the previous monitor was micro stutter.
So my guess is I would really like 240 Hz Freesync screen with good overdrive, if only my pc could push constant frames like this in games... But I don't want to upgrade it... I want to keep it until it's unplayable and really upgrade as late as I can.
Big update... VG278QR is giving me eye strain... I had to give it back. No matter the parameters I tried, 2 hours max on the screen and then I have to stop, and wait for the strain to go away. Very strange. So yeah, monitor might be the most important part of the computer... with the chair too (back problems...)
For text and general use, the thing that partially solve the problem for me, strangely, is putting it on max inverse tilt -5%, top monitor the closer, and bottom far. It's ok but then in games, it doesn't help for included text for me, and image is strange.
There is something in the sharpness, I might be very very picky about this, seems that from a point of view, the whole screen has too much variation, going from the center. Maybe it's also a vision angle / sensitivity too.
Needless to say that it is a disapointment, but might as well be a thing to remember next time I want help to stop being in front of a computer...
So... I had a Iiyama, and went to test the current Iyama line.
Could see the GB2560HSU-B1 and the GB2760HSU-B1. Well... Saved !
Compared to the GB2488HSU-B1, I immediately felt the similarities.
The 25' is really similar. No eye strain for me, sharpness is great and could even be tuned in OSD.
Overdrive is good, really on par with the previous model, not seen in games, only in text, but small.
Sound system is more powerful that GB2488, that's what I wanted, and now it's enough for a small office, but quality is a bit lower, unfortunately. I wonder if the non oblique plastic frame compared to the speakers increases the echo sort-of effect.
Freesync with nVidia card is working okay, but only did a short test.
And the 27' is great too ! No eye strain even with increase of size and pixel, sharpness is similar, I wanted a bigger version of the GB2488 and it is. Overdrive is good as well, but with increase of pixels size, you see it just a bit more with text, still not in games.
Sound system same than the 25' it seems. Freesync working as well with nVidia card.
No more grey filter on the whole screen, blacks are really blacker, so better contrast, waouh effect still, but just a bit less than the Asus.
I am a novice, but from what I saw, I can tell Iiyama does "calibrate" their monitors, in the same way. Pixel sharpness is really close on the 3 models (and viewing angles ?), so no eye strain for me. And colors too. I opened an Excel file with color columns, and on the Asus the displayed result was really different. No that important for me, but on the 3 Iiyama, the results were pretty close, with the 2 newers one, given the contrast, much more vivid for powerful colors.
I guess next time I will go the easy way, and from now on only buy Iiyama, I am too used to them.