Talk:Defective pixel

Defective pixels are not limited to displays

CMOS and CCD image sensors have defective pixels. Definitions seem to be vendor specific and contained in proprietary documents. With these there can be hot pixels, bright pixels, dark pixels, and dead pixels. In addition, there can be clustering or grouping of pixels and the location zone of the defective pixels is important in the image quality.

Frame grabbing, GPU memory, and other buffering can have these four plus defective bits or bit scrambling, this is rare but is this author has experienced it happening in an SoC. This topic either has to be re-titled to "Display Defective Pixel" or the other cases need to be included as well as the general description of the four sub-classes. Active pixel displays would likely have these four classes.

The ISO 13406-2 definition should be generalized to cover the four cases with a citation that three match the ISO definitions.

It should be noted that EMVA 1288 defines defect pixels as thus:

4.3 Defect Pixels As application requirements differ, it will not be possible to find a common denominator to exactly define when a pixel is defective and when it is not. Therefore it is more appropriate to provide statistical information about pixel properties in the form of histograms. In this way anybody can specify how many pixels are unusable or defect using application-specific criteria.

The EMVA uses logarithmic histograms to view the defect pixels. They provide the rationale as: It is hard to generally predict in how far a deviation from the model will impact the final applications. Some of them will have human spectators, while others use a variety of algorithms to make use of the images. While a human spectator is usually able to work well with pictures in which some pixel show odd behaviors, some algorithms may suffer from it. Some applications will require defect-free images, some will tolerate some outliers, while other still have problems with a large number of pixels slightly deviating.

A synopsis of the EMVA definition and the rationale should be provided as they apply to displays a well as sensors or buffer/memory.

Defective subpixel on a CRT

Not only LCDs can have defective pixels, I have a CRT with a defective subpixel.

Dead subpixel on a CRT

– \ldblquote 21:43, 15 September 2007 (UTC)

well...

That's definitely very interesting, but could be misleading to people who don't understand the difference between a CRT and an LCD. An LCD's defective pixels are due to dead electronics right there, actually at that pixel on the screen, versus this CRT's problem is that something is probably blocking the shadow mask... all of the actual electronics are ok, as they are located in the back of the monitor. Has this monitor been moved around a lot, possibly layed face-down?

Good image capture, by the way. 130.22.190.5 22:14, 25 September 2007 (UTC)

The subpixel is dead since I bought the display (new) about 6.5 years ago. I don’t know what they did with it before I bought it :) Today I ask myself why I didn’t complain about it during the warranty period. – \ldblquote 23:47, 20 October 2007 (UTC) —Preceding unsigned comment added by 91.4.28.156 (talk)

I've seen this on a few CRTs myself, including an old Mac Color Classic in my collection. Those use Trinitron tubes, BTW. I wonder if it could be fixed by laying the monitor on its back and tapping on the glass front? Jax184 01:14, 8 November 2007 (UTC)

Also, subixel is not the correct word, because CRTs don't have fixed pixels. The thing, which is blocked is just a hole in the shadow mask. See shadow mask for details. --MrBurns (talk) 06:50, 17 October 2008 (UTC)

thanks!

I've just noticed a stuck pixel on my rather new 22inch lcd monitor. I can definately confirm that gently rubbing the screen cleared it! thanks to whoever wrote that!--82.3.237.170 (talk) 18:37, 11 December 2007 (UTC)

confirmed

I thought I got oken" lcd off ebay with several "dead" pixels, now with using those "flashing"-tools and (not very) softly rubbing on the stuck pixels they magically turn alive again, almost all of them, I'm glad. —Preceding unsigned comment added by 85.177.205.149 (talk) 02:36, 25 July 2008 (UTC)

Samsung

"Samsung conforms to ISO 13406-2 to replace any dead pixels within 14 days": from what I read the ISO 13406-2 says nothing like that —Preceding unsigned comment added by 130.60.155.213 (talk) 16:44, 19 February 2008 (UTC)

Hot Pixels

In photography, a hot pixel can also refer to a pixel that will show up red in long exposures due to higher than normal charge leakage. Source Source —Preceding unsigned comment added by Major Small (talk • contribs) 20:55, 1 June 2008 (UTC)

Yes, this seems to be a fairly notable usage that should probably receive its own page.--71.104.225.218 (talk) 01:54, 24 February 2010 (UTC)

Self-contradiction

In the Dark dot defects/Bright dot defects section, it's claimed that a pixel that is in the "on" position blocks light from coming through, which leaves a dark spot, whereas a pixel that is "off" lets light through and creates a bright spot. This coincides with my understanding of how LCDs work, and I've read it from other sources as well. However the Stuck versus dead pixels section states the opposite:

"In a dead pixel, all three sub-pixels are permanently off, producing a permanently black pixel. Dead pixels can result from similar manufacturing anomalies as stuck pixels, but may also occur from a non-functioning transistor resulting in complete lack of power to the pixel."

—this contradicts what is stated in earlier sections. There is also no citation for this, and the entire section seems to be of dubious probity.--71.104.225.218 (talk) 02:09, 24 February 2010 (UTC)

Linked Pixels

There is a a 4th type of defective pixel, a linked pixel where its color is determined by other pixels on the screen. This type of defect is also see in computer memory cells. Example: My monitor has 1 linked pixel that is red under special circumstances. The brightness of the linked pixel is the summation of the brightness of the column of pixels beneath it. The defective pixel cannot be observed with any standard solid color backgrounds (black, white, red, green, blue, magenta, yellow). —Preceding unsigned comment added by 63.236.116.94 (talk) 23:21, 5 December 2008 (UTC)

What about a cyan background? — Preceding unsigned comment added by 2A01:119F:21D:7900:4186:8B62:D199:F471 (talk) 07:33, 19 July 2019 (UTC)

Insects/bugs

Maybe it would be useful to add to the article that it's actually fairly common to have dead or live bugs trapped inside the screen. I've searched google to find out exactly how rare this is, and it appears to happen quite often. Dead insects apparently are commonly mistaken for dead pixels. --80.61.251.174 (talk) 15:18, 20 June 2009 (UTC)

Outdated?

I've been looking around for some statistics on defective/dead/stuck pixels and almost all information on the net is pretty old, dating earlier than 2010. This supports my theory that the industry has all but eliminated this problem. What i'm still sometimes hearing of is hot/cold pixels on image sensors, and even that lesser issue seems to be quite rare nowadays. I would like to update the article accordingly, but since a non-problem doesn't draw media attention, it is hard to find reliable sources. Mumiemonstret (talk) 11:00, 18 June 2014 (UTC)

In the case of sensors, the problem has not been eliminated and the vendors each have their own definition. The EMVA 1288 definition of defect pixels provides more of a problem statement: As application requirements differ, it will not be possible to find a common denominator to exactly define when a pixel is defective and when it is not. Therefore it is more appropriate to provide statistical information about pixel properties in the form of histograms. In this way anybody can specify how many pixels are unusable or defect using application-specific criteria

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Flat-Earther claims

Are hot pixels what flat-Earthers claim to be stars shining through the Moon in their photos? serioushat 02:27, 14 September 2019 (UTC)

Is it actually possible to fix them - serious and professional tests or research.

Hi all,

Has anybody encountered a serious research or test on whether any of the method you can commonly encounter on the internet work? I'm thinking about flashing bright colors on the screen, rubbing it, warming it up, etc, like for example those described in part 2 here: https://www.wikihow.com/Fix-a-Stuck-Pixel-on-an-LCD-Monitor

I think it would be a very valuable addition to this article, especially considering the fact that there is plenty of dubious methods popping out in search engines, texts whose authors often show lack of understanding of the technology involved, while I couldn't find any serious and critical test of those methods. Or at least technical explanation why would or wouldn't they work. After searching for over an hour, I am myself confused. And this time, unfortunately, Wikipedia didn't help.

Borys1703 (talk) 12:20, 9 February 2020 (UTC)

"Stray pixel" listed at Redirects for discussion

The redirect Stray pixel has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 August 20 § Stray pixel until a consensus is reached. Doerakpoes (talk) 15:51, 20 August 2023 (UTC)