Understanding local dimming zones

[Things change I've changed]

I'm researching older 38" gaming monitors, for example I'm temped by this,

LG 38" 38GN950P-B 3840x1600 NANO IPS FreeSync G-Sync Compatible 160Hz 1ms HDR 600 Curved Gaming Monit

Order LG 38" 38GN950P-B 3840x1600 NANO IPS FreeSync G-Sync Compatible 160Hz 1ms HDR 600 Curved Gaming Monit now online and benefit from fast delivery.

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The screen only has 12 dimming zones, looking at videos of this online if example there is a bright object in the corner of the screen with a black background that whole area around the object lights up which looks very bad, what I don't get is what is this achieving?, the reason I say this is if I have that same scenario on my current old X34 with no local dimming zone I don't suffer this problem and the screen looks to my eyes 'fairy' black around the bright object with no light bleed? It makes no sense to me, can this feature be turned off, and if it can I assume it would then act similarly to my current screen?

 

[willhub]

Is your monitor a VA panel? They have better blacks, or could just be your monitor whatever is better at blacks, but it won't be dark on a black screen fully.

My dell has very small number of local dimming zones, but HDR is still better despite what people say because it give enhanced brightness and contrast but you do notice the blooming around certain things but it doesn't bother me.

 

[Things change I've changed]

It's an IPS panel, I'm just struggling to see the benefits, look at this image for example,

You see where the screen is lit up up the left where the mouse is, are you saying with local dimming disabled the whole screen would be that grey? I have never witnessed any monitor without local dimming zones to be that poor at blacks, or is this due to the HDR brightness?

 

[willhub]

LCD panels can't compete with OLED for deep blacks but try to get as near with local dimming. You won't get an LCD hitting actually black such as an OLED panel where the pixels are off.

The simple fact is the local dimming is designed to turn the screen off and only illuminate what is on the screen, for example a circle on a screen moving, and because the local dimming zones are not granular enough this is why you get "blooming"

 

[jwilliamson47]

I've tried two AOC miniled monitors. Despite the IPS one having a lot more zones than the VA and being lmost twice the price, the VA looked miles better. The contrast looked amazing with local dimming on strong and slight blooming.

The IPS model had awful blooming displaying logos and the contrast seemed mediorce to my eyes even with the max local dimming setting. It's possible the IPS one i got was a dud but just sharing my experience.

 

[Five.Stars]

It's an IPS panel, I'm just struggling to see the benefits, look at this image for example,

You see where the screen is lit up up the left where the mouse is, are you saying with local dimming disabled the whole screen would be that grey? I have never witnessed any monitor without local dimming zones to be that poor at blacks, or is this due to the HDR brightness?

I think that photo is slightly exaggerated by the curvature of screen, but yeah any screen with dimming zones with cause halo'ing. This is obviously mitigated by having a larger amount of dimming zones. My 34" Ultrawide has 56 zones, but it isn't enough and having got myself an OLED tv last year has made me consider upgrading to a similar sized 21:9 OLED.

 

[Vexr]

It's an IPS panel, I'm just struggling to see the benefits, look at this image for example,

You see where the screen is lit up up the left where the mouse is, are you saying with local dimming disabled the whole screen would be that grey? I have never witnessed any monitor without local dimming zones to be that poor at blacks, or is this due to the HDR brightness?

Sorry for the necro. Did you get one of these LG panelled 38" monitors or find out anything more?

I've just got an Acer Predator X38S and am a bit taken aback by the same overzealous local dimming zone shenanigans you've shown here. Turning off local dimming just turns the dark areas of the screen washed out and overlit all the time, instead of just when something bright appears in that zone, so that's not an option.

Annoyingly, a bright thing on the screen doesn't even benefit much when its zone lights up, washing out the surrounding blacks. I wish there was a setting on the monitor where it would only brighten up the zone when 60%+ of the pixels in it would benefit / a significant amount of other pixels in the same zone aren't very dark in comparison.

 

[Vexr]

Had an interesting moment in SOTTR where there was a lot of bright white text on a black background, but no bloom. Then I moved a very default windows looking cursor over the same area, and up came the backlight bloom.

Starting to think it's the Windows 10 HDR implementation that is the issue here. I finally have a reason to upgrade to Windows 11 if that will improve it.

 

[EsaT]

Had an interesting moment in SOTTR where there was a lot of bright white text on a black background, but no bloom. Then I moved a very default windows looking cursor over the same area, and up came the backlight bloom.

Starting to think it's the Windows 10 HDR implementation that is the issue here. I finally have a reason to upgrade to Windows 11 if that will improve it.

At least smaller text has very narrow figure, so maybe it didn't have enough many side by side bright pixels to trigger boosting of backlight's brightness.
Local dimming algorithm has big effect to how it works.
For example "dark biasing" helps to avoid/minimize visible blooming... At the expense of smaller highlights not getting full brightness.

Anyway edge illumination is total BS for local dimming and FALD backlight is needed for local dimming to have any actual value.

 

[Vexr]

A reasonable theory regarding the text being too small to bloom the backlight while the cursor still can, but checking a screenshot that can't be the case.