Request for help to IPS monitor owners - please make videos to better evaluate angular backlight uniformity

[midix]

Hi everyone.

 

I would like to ask the community for help. If you have an 24 - 27 inch IPS monitor (especially, if you have bought it in recent months or last year), then please do the following:

 

- you will need a camera; even a cell phone with 5 MPx camera might work just fine

- open a solid color image; yellow should work fine; you can also open this image in the spoiler block:

Spoiler

just zoom it in using Ctrl+mousewheel, so it fills entire screen area and hit F11 on your browser to go fullscreen

 

- now turn on your camera and position it at a distance when entire screen fits in the frame and then move the camera up and down, and also try to slightly rotate vertically to record the screen from different angles

 

- put your camera closer, about 25cm (10 inches) to your screen and repeat the procedure. Also try to put your eyes at the same distance and if you notice any brightness shifts which are not visible on your camera, try to change your camera position, orientation or distance to make the brightness shifts to look more similar to how you see them with your eyes

 

- upload your video somewhere (Youtube, Vimeo, Google Drive, OneDrive, Dropbox - you choose) and post the link in the comments of this topic.

 

This test will be more objective if you have more than one IPS monitor and can compare them side by side.

 

Important notice to avoid misunderstandings:

I do not ask you to reproduce tests which can be found on numerous popular LCD test sites such as tftcentral. My test is exactly to capture the issue which is being ignored in almost all other reviews I've seen. Also I do not ask you to measure minor manufacturing differences between monitors of the same make/model. This test is about comparing different models with different IPS panels and backlight systems.

 

The purpose of these operations is to capture any brightness shifts which manifest themselves on solid color background. Unfortunately, most reviews and videos are using colorful images which mask the brightness shifts and thus do not correspond to the percepted visual image I see when working with documents, web pages etc., which usually have solid color background.

 

This process will take just 10-20 minutes of your life but it will save me (visually impaired programmer since birth) some frustrations and numerous monitor returns. Besides, I think the results of this test will be appreciated also by other professionals (programmers, designers etc.) who would like to find the best of IPS monitors. Or this might just be somewhat educational to show people that there are more important differences among IPS panels than just the ones loudly advertised by manufacturers (contrast, reaction time, refresh rate, color bit depth). What's the use of all the advertised goodness if your brand new expensive monitor loses in some aspects when compared to some older and cheaper IPS monitor? When I pay premium, I expect to receive an upgrade in every aspect, and not some upgrades+some downgrades. It's a shame to see how manufacturers don't learn from each other and launch models with defects which have been fixed by some other manufacturer (or even the same manufacturer) long ago.

 

As my experience shows, the price is not always an indicator. Even some brand new mid-level IPS monitors (such as Asus ProArt series) might turn out to be worse in terms of backlight and brightness / contrast uniformity than some budget or older models, despite that more expensive models have more color bit depth and better calibration.
 

Here is my older video which clearly demonstrates how brightness shifts on a new Asus ProArt can be worse than on some old Viewsonic:

 

 

 

 

 

I have previously created a thread, but it contained too much distracting details and I did not think of the solution immediately. If you want to know the long story behind my request, then you are welcome to read the following thread:

 

 

Thanks in advance to everyone for help.

 

 

[MrSuperb]

This test is pretty useless, as it would vary between different screens of the same make/brand.

 

IMHO tftcentral.co.uk does a far better job, than any video could do, as they actually measure the uniformity ...

[midix]

The problem with  tftcentral.co.uk is that they don't measure how perceived backlight brightness change when viewed from different angles on a solid background. The accent being on angles .

 

I don't need a simple direct uniformity test - for that I know that there might be some noticeable differences, and there are already plenty tests out there. If you look at my video, you might notice, that from a distance and at straight angle the difference between both screens is not that big to be concerned about. Only when I move camera closer to the screen, then you notice that the screen on the left looks more even, like being lit by far-away evenly distributed light, while the screen on the right starts looking more like being lit by a spot light creating shadows at edges.

 

I have compared two ASUS ProArt PA238Q (I don't have video, sorry) and while their general backlight uniformity differs at some screen areas, still they both have the very same spot-like behavior when being looked at from a closer distance at solid backgrounds.

But the older Viewsonic VP2365WB (which has a cheaper e-IPS panel) does not exhibit such issue, and that is why VP2365WB is much more pleasant to use, at least for my eyes.

 

When I read a text on VP2365WB, it feels more like reading an evenly lit sheet of paper, but PA238Q in comparison feels like reading a sheet of paper being lit by a flashlight which points to the area I look at. The center is bright, but it starts getting darker at edges.

I have used to such behavior on TN displays, but I didn't expect it from a brand new IPS monitor, especially after my experience with VP2365WB. This behavior seems to be not a minor difference from screen to screen of the same make/model, it seems more like a principal difference in backlight or panel structure and mechanics.

 

Now I would like to upgrade to something larger, 27", but I'm afraid that I won't be able to find a monitor which has the same evenly lit image of VP2365WB, therefore I need some help, so I could immediately cancel out some potential candidates before buying.

[midix]

Ok, suggesting from responses, it seems nobody understood what I want. I'll try to explain with more visual details.

 

Let's assume we have two monitors. Both are IPS from different brands. The left one is some cheap e-IPS panel. The right one is more expensive, better IPS panel.

 

Let's say we look at them from a far distance. They look like this:

 

 

Let's say, the expensive one might look somewhat brighter because it has higher contrast ratio.

 

Now let's get closer to the monitors and try to look at solid color. But here's a catch - let's get closer than normal people look. Let's look at it from 25cm distance and see how it looks:

 

 

 

See? The right one exhibits weird behavior - it looks like being lit by a flashlight and the image is bright at the center but gets darker fast at the edges. This was very typical for old TN displays. The problem is that you would suffer from this issue only if you look from somewhat closer distance than usual and only on solid color backgrounds.

Also, it it tricky to capture this problem on a camera - you would need to fiddle with manual exposure settings to get it right.

But what I found, is the following: monitors which have this issue, also have much worse brightness distribution when looked at from the top side.

See the next picture:

 

And to prove that this is not just artificial situation, here is a snapshot from my video with real monitors:

 

 

 

 

The vertical angle is not that large, but the monitor on the right already shows clear signs of getting darker to the bottom while the left monitor remains pretty evenly lit.

 

I don't know if this is backlight issue or the infamous IPS glow issue, I know only that there are models which exhibit the issue and there are models which do not, and the price does not matter (of course, if only we don't talk about expensive Eizo and NEC professional displays).

So, I really want to find a monitor which does not have the issue, therefore I need your help.

 

[midix]

It seems, I have found the source of the issue. It might have something to do with the quality of backlight diffuser films.

Here is a video from a person who has disassembled some LCD panels to use as fancy lighting source for his room:

 

 

As you see, he compares two panels - one with diffusing layers intact and another with everything stripped away. The difference is obvious - those layers cause visible light intensity changes when looked at from different angles and distances.

 

But still I'm not sure, why not every LCD panel has the same issue. I mean - all of them have almost the same backlight diffusing panel&film system, don't they?

[Mira Yurizaki]

Well I didn't run your test to the letter and I didn't record a video of it, but I can tell you two things about my laptop display, which has an IPS panel:

• Changing the viewing angle along the horizontal axis shows a slight brightness drop.
• Changing the viewing angle along the vertical axis shows a slight brightness drop, but then it gets brighter the further I go.

However there could be a simple explanation for this: the light coming out of an LCD after going through everything is polarized and going straight out. And it appears even before the polarizers, the system tries to give you light that shoots out normally (as in a surface normal or directly out). But why isn't it uniform? I dunno.

I was going to say the surface material matters (matte or glossy), but my phone exhibits slight brightness shifting when viewed off angle.