White shadow with LCD Monitor text

[google_groups]

I wondered what was making single pixel checker-board patterns shimmer
on my desktop's analogue LCD monitor (Samsung 712N), though not my
laptop (which would have a direct digital connection from the video
card.) So, after a Google search, the following website:

http://www.techmind.org/lcd/phasing.html

helped me tune the clock/phasing of my analogue LCD monitor, and
eliminate the shimmering. But, when I had got that problem fixed, black
text on a white background would have a very small, but noticeable
(brighter) white area to the right of characters. See the image at the
following link for an exaggeration of what it looks like:

http://www.geocities.com/simonclarke/image.gif

This problem could be reduced, but only by putting the clock/phase out
of sync again. I'm going to call Samsung tech-support, but I'm
wondering what's causing this "white shadow" problem, and if possible
how to rectify?

If anybody needs any clarification, or more information please let me
know.

Thanks in advance for any replies,

Miner2049er.

 

[chris]

I wondered what was making single pixel checker-board patterns shimmer
on my desktop's analogue LCD monitor (Samsung 712N), though not my
laptop (which would have a direct digital connection from the video
card.) So, after a Google search, the following website:

http://www.techmind.org/lcd/phasing.html

helped me tune the clock/phasing of my analogue LCD monitor, and
eliminate the shimmering. But, when I had got that problem fixed, black
text on a white background would have a very small, but noticeable
(brighter) white area to the right of characters. See the image at the
following link for an exaggeration of what it looks like:

http://www.geocities.com/simonclarke/image.gif

This problem could be reduced, but only by putting the clock/phase out
of sync again. I'm going to call Samsung tech-support, but I'm
wondering what's causing this "white shadow" problem, and if possible
how to rectify?

The 'ghosting' problem could be casued by a poor quality monitor cable or
video card. Is the cable securely connected?

If your monitor has a DVI connection you shouldn't get this problem - though
normally even the standard VGA connector is OK.

 

[Mxsmanic]

This problem could be reduced, but only by putting the clock/phase out
of sync again. I'm going to call Samsung tech-support, but I'm
wondering what's causing this "white shadow" problem, and if possible
how to rectify?

Probably a lack of bandwidth in the video card. The modulation
overshoots a bit on fine details and you get white or black shadows of
small details of opposite color.

You can eliminate these problems by using digital input to the LCD,
although that requires an LCD and video card that produce and accept
digital signals, and digital signals have limitations of their own
(indeed, the original monitor signals back in the CGA/EGA days were
digital, but they were replaced by analog for greater flexibility--now
the bandwagon has made another U-turn).

 

[Bob Myers]

Probably a lack of bandwidth in the video card. The modulation
overshoots a bit on fine details and you get white or black shadows of
small details of opposite color.

Unlikely, although possible. Far more commonly, this is
the result of an impedance mismatch or discontinuity in the
video cabling and connector. (The definitive test is to try a
different cable, preferably of a different length, and see if that
affects the problem - even if it is only to move the shadow
relative to the edge that's causing it.) Cures, if it IS the
cable/connector, is to find a better cable, eliminate all
unneccesary discontinuities in the signal path (i.e, video
switches, or using several cables "daisy-chained" together
rather than a single long one), etc.. Or, of course, switching to
a digital interface such as DVI, if that's an option for you.

Bob M.

 

[google_groups]

Thanks for all the replies so far folks - here's the latest.

I have yet to try another video cable as suggested, but yesterday
(March 17, 2005) I called Samsung tech support, and described the
problem as I have above.

I spoke with Jason, a representative in the Louisiana customer care
dept. who told me that "Samsung are aware of such a problem with this
monitor", and they are sending me a replacement monitor.

Let's see how that one looks.

Miner2049er.

 

[google_groups]

So, an update. The replacement monitor that Samsung sent (a refurbished
unit) had less of the problemtatic white shadow, but had an
always-bright-green pixel right in the middle of the screen.

But, Samsung hadn't gotten my original purchased-new monitor back yet,
so that went back to Office Depot, and they swapped it out for another
new one. And Samsung are getting the replacement unit they sent
returned.

The second monitor from Office Depot also has better video than the
first, and no dead pixels. So it looks like I'll be keeping that.

Miner2049er.