Monitor brightness switching bright (2-3 secs) to dim (long term) as I move mouse

Windows 11 current
Nvidia Geoforce GTX 1660 Version 46.17 (latest download)
Two monitors - both BenQ - EW2780 (2560 x 1440) and PD2700 (3840 x 2160). The latter is main VDU (Monitor 1) and the problem one. The former works OK.

Problem - Only affects one monitor - the one set as main or monitor 1.
Monitor 1 the default brightness is usually low. However moving cursor to area around top right or togglingto another app brings brightness up to normal wanted level but only for 2-3 seconds then it switches back to dimmer unwanted level.
Brightness on monitor control is set at high. Night light is off so shouldn't be causing this (my room currently sunny).
I have updated and reinstalled Nvidia driver.

Have I missed something or is bad news re video card.
NB - my other recent thread re font sizes.

That sounds like something to do with Dynamic Contrast. Games and Video usually benefit from Dynamic Contrast, but now WIndows 11 can also benefit. It could be, if you have customised the brightness on the one monitor, then that has thrown the monitor's or Windows 11 algorithms. For sure I do not know, but I would start investigating along those lines before you suspect a faulty graphics card. Even consider doing a factory reset of the one monitor, and see if that makes a difference.

Been in touch with BenQ but their suggestion was to switch off the auto dimmer function but that was already off.
Odd thing is that it seems to affect Google and WhatsApp mainly but unfortunately not consistently. I say unfortunately because I can't posta definitive list of the problems I am experiencing - they can vary. Also odd that other monitor not affected - that points to a monitor issue, but apps affected points to a software issue.
I note Ike's suggestion but I haven't customised anything. I'll try the factory reset but will need to find and consult manual for the monitor as I don;t know how to do that in this case.

Hi @Sigurd

Sigurd said:

I'll try the factory reset but will need to find and consult manual for the monitor as I don;t know how to do that in this case.

Click to expand...

I had a quick look at the manual, and I can see the monitor has a reset all option on page 51. Instructions on how to get to this option are a bit hard to fathom without the exact same monitor to try out; but it is documented on page 48 of the same manual.

The user manual download page can be found here:

That hasn't solved the problem, but in the course of trying various other settings I solved it - rather contra-intuitively.
The effect seemed as if the auto dimmer facility on the monitor was malfunctioning, hence BenQ's suggestion of turning it to off. It already was off. So, as I said, somewhat illogically I decided to turn it on. Problem gone!