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Comment by wakeupcall | Hacker News Reader

I observed an interesting effect.

I left the "palette demo" flickering on the same spot for about 5 minutes while doing other stuff on a dell up2720.

After closing the page, the pattern was still visible on the LCD when showing a grey image (or on top of the same pattern again where ghosting became quite visible). It's visible both as a slight color shift but mostly flickering.

Putting the screen to a fixed color pattern (via LCD conditioning) was still showing the same, again mostly on grey, excluding thus most of the driver/display chain as an issue which I suspected as first (dirty cache).

The effect is gone after about 5 more minutes.

First time I see persistence like this on an LCD. A static flat image can't do this on this panel.

Can anybody reproduce the same?

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I've had the same thing happen after an extended period of emulating an Amiga in an interlaced screen mode. After exiting the emulator, there was still similar flickering and mild image retention, that also faded after a few minutes.

My guess is that it's down to the relationship between the specific interlacing used by the panel, if any (lagom.nl has inversion/pixelwalk tests to determine which type a monitor uses), compared to the 60Hz flickering. Something about the two together induces image retention far sooner than the average content, albeit image retention that also fades much quicker.

>but mostly flickering

Trivia: static images on LCD can be sometimes seen as flickering because they are not really static, to prevent burn-in and subsequent damage polarity is reversed every frame. Some details here: http://www.techmind.org/lcd/

My digital signage screen that I use as a monitor with an official 18/7 uptime rating has explicit temporary burn in/ghosting issues mentioned for content that is too static/persistent, and says it'll go away after a bit of rest time/waiting for the LCD to normalize. It even has an anti-burn-in mode that steps the image around+-4 pixels in both directions every few minutes to prevent any hard contrast lines from persisting and their ghosting to be notable to the customers of the facility that operates the digital signage.

What you describe is regular burn-in, but this is not just burn-in.

Leaving a static image for >30m has no visible effect on this panel.

In this case it's the flicker itself which persists on _top_ of a slight color shift, and requires only a few minutes of exposure.

I tried this on another older dell IPS panel and I observed the same. Quite interesting!

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