Distorted display of a flat CRT monitor

[letterzone]

I recently bought a new 17" flat CRT monitor (SyncMaster 793MB,
Samsung). The images are perfect in clarity and colors but distorted in
shape. This distortion is not noticeable in pictures and videos but
alarmingly obvious in geometrical figures. All meant-to-be straight
horizontal and vertical lines except those which pass through the
center of the screen are curved--they sag at their middle towards the
center of the screen. This sag is more prominent in the horizontal
lines than it is in the vertical ones, and it increases as the distance
of a line from the centre of the screen increases. Being measured with
a ruler, the maximum sag in any line is about one millimeter. I have
tried all available options on the settings panel but could not correct
this distortion.

1. Do all flat CRT monitors display such distortion--is this a
limitation of flat CRT monitors of this age?
2. Can this distortion be removed by any setting given inside the
monitor?
3. My vendor has shown helplessness: will it be fruitful to send it
back to the dealer or company to remove this distortion?

Please answer soon so that I might not be too late in changing or
returning the monitor in question.

Thanks,
Gyan

 

[Rick Wintjen]

I recently bought a new 17" flat CRT monitor (SyncMaster 793MB,
Samsung). The images are perfect in clarity and colors but distorted in
shape. This distortion is not noticeable in pictures and videos but
alarmingly obvious in geometrical figures. All meant-to-be straight
horizontal and vertical lines except those which pass through the
center of the screen are curved--they sag at their middle towards the
center of the screen. This sag is more prominent in the horizontal
lines than it is in the vertical ones, and it increases as the distance
of a line from the centre of the screen increases. Being measured with
a ruler, the maximum sag in any line is about one millimeter. I have
tried all available options on the settings panel but could not correct
this distortion.

1. Do all flat CRT monitors display such distortion--is this a
limitation of flat CRT monitors of this age?
2. Can this distortion be removed by any setting given inside the
monitor?
3. My vendor has shown helplessness: will it be fruitful to send it
back to the dealer or company to remove this distortion?

Please answer soon so that I might not be too late in changing or
returning the monitor in question.

Thanks,
Gyan

This is known as pincushion, and many monitors have an adjustment for
this in the on-screen settings, along with size, contrast, and
brightness. If this adjustment isn't included, take it back for a
replacement.

 

[letterzone]

I know about pincushion. Pincushion setting is only for distortion in
vertical lines--I could not find a CRT monitor that has pincushion
setting for correcting the curvature in horizontal lines--and it is
applicable only till the vertical sides of the display are curved. The
distortion I have described in my post exists despite making all
possible settings from the OSD, even if the display is absolutely
rectangular in shape and there is no tilt in it. Yes, I took it back
for replacement, but when I studied the display of flat monitors
manufactured by two other companies, I found similar distortion in both
of them; so I have brought my monitor back home with the hope that the
technology might improve by the time I buy the next flat CRT monitor.

 

[Not Gimpy Anymore]

I know about pincushion. Pincushion setting is only for distortion in
vertical lines--I could not find a CRT monitor that has pincushion
setting for correcting the curvature in horizontal lines--and it is
applicable only till the vertical sides of the display are curved. The
distortion I have described in my post exists despite making all
possible settings from the OSD, even if the display is absolutely
rectangular in shape and there is no tilt in it. Yes, I took it back
for replacement, but when I studied the display of flat monitors
manufactured by two other companies, I found similar distortion in both
of them; so I have brought my monitor back home with the hope that the
technology might improve by the time I buy the next flat CRT monitor.

Sadly it is deficiency in the design of the scan linearity, and does
indeed
seem to be present on just about any "flat CRT".
Some things to note:
1. These "flat" CRT's are a bit of a misnomer - the front face is flat,
*BUT* the phosphor surface on which the image is formed is NOT.
2. The phosphor surface is indeed "flatter" than traditional CRTs but it
has some funny saggital dimensions that render it "non-spherical",
hence it would get very very involved to design a scan circuit that
would have the correct linearity to minimize the geometric
distortion.
3. The original Zenith FTM tube *was* fully flat, but was considered
too expensive to build, so the "poor man's flat CRT" was developed.
4. If you really need geometric accuracy, a CRT is the least recommended
technology to consider.
5. Frankly, I think you need to abandon any hope that CRT technology
will ever improve - the economics just do not support further
developments
in CRT technology - CRT companies are "changing horses" or closing
their doors. CRTs may remain for a while to support the extremely
sensitive economics of "3rd world markets", but those displays will
also
remain on the extreme bottom of the performance heap, and will
continue
to sell only because they are still the lowest cost option available.
Power
users are repidly running out of viable products to fill their needs.

Sad but true - even Sony is exiting the performance CRT market.

Rgds,
NGA

 

[Kevin]

I know about pincushion. Pincushion setting is only for distortion in
vertical lines--I could not find a CRT monitor that has pincushion
setting for correcting the curvature in horizontal lines--and it is
applicable only till the vertical sides of the display are curved. The
distortion I have described in my post exists despite making all
possible settings from the OSD, even if the display is absolutely
rectangular in shape and there is no tilt in it. Yes, I took it back
for replacement, but when I studied the display of flat monitors
manufactured by two other companies, I found similar distortion in both
of them; so I have brought my monitor back home with the hope that the
technology might improve by the time I buy the next flat CRT monitor.

If you want a geometry distortion free monitor then you should buy an
LCD.

 

[nutso fasst]

Sadly it is deficiency in the design of the scan linearity, and does
indeed
seem to be present on just about any "flat CRT".

I have a 21" Philips flat CRT, an acquaintance has a 17". Neither has any
noticeable curvature along the scan lines.

nf