Color difference between Monitor and TFT displays

Color difference between Monitor and TFT displays

Post by Stan » Tue, 11 Dec 2001 13:00:12



I'm doing some rendering and I am finding that there is a huge difference in
color between my TFT (laptop) display and my monitor.

I am working with TBitmaps and L.A.B color space for brightness control and
converting back to RGB.

Is there any solution to getting the colors to look more or less the same on
both displays?  Is this the fault of my code or simple brightness and
contrast adjustments on the displays?

Stan.

 
 
 

Color difference between Monitor and TFT displays

Post by Nick Rya » Tue, 11 Dec 2001 19:26:30


Quote:> I'm doing some rendering and I am finding that there is a huge difference
in
> color between my TFT (laptop) display and my monitor.

> I am working with TBitmaps and L.A.B color space for brightness control
and
> converting back to RGB.

> Is there any solution to getting the colors to look more or less the same
on
> both displays?  Is this the fault of my code or simple brightness and
> contrast adjustments on the displays?

Most video drivers have colour and contrast controls - this is because the
exact outputs of each card may vary (and may even vary between batches of
the same card due to slight differences in the electronic components used).
Some drivers also have loadable colour profiles for selected monitors to
help alleviate this problem.

Getting an exact colour match between monitors is extremely difficult, if
not impossible - to explain, the colour output goes through the following
stages before hitting your *subjective* eye:

1. RGB values in the card are converted by the video driver into the
internally used values - this process takes into acount the gamma and
contrast settings in the drivers. There is often additional innacuracy here
depending on how how the hardware stores the values as converting between
RGB and HSV isn't an excact science.

2. Once the colour values are in the card's internals the signals are
converted into the  video output (usually analogue) - the differing specs of
electronic components on the board can affect how this happens - also some
video drivers make their gamma and contrast changes at this point.

3. The video signal travels up what is usually a fairly cheap bit of wire
and connectors, the quality of this part can also affect the signal as can
external factors such as running the cable close to large magnets such as
monitors(!), telephones and speakers.

4. The signal then typically gets processed again by the electronics of the
monitor - theres more variance here due to the electronic components used -
before it hits the display which you should also treat as another variance
as the batch, model and age of the CRT can make a difference to the colour
output.

5. The last step is the environmental factors based on factors such as the
ambient lighting, the colour of clothes you're wearing (reflection off them
of the screen) and even how clean the screen is. Applying a CRT screen
filter also makes a very dramatic difference...

...so basically your best best is tweak the display driver / monitor
settings by eye so that the images look roughly the same... :)

Nick

 
 
 

Color difference between Monitor and TFT displays

Post by Stan » Tue, 11 Dec 2001 21:20:39


Nick,

Thanks for the info.  It was very informative and pretty much what I already
thought.  So,  basically,  if I make a really nice rendering on my machine,
doesn't mean the end users will see the same thing - shame.

Regards

Stan.

 
 
 

Color difference between Monitor and TFT displays

Post by ADS » Tue, 11 Dec 2001 21:36:08


Do you use a ICC engine for this?

Quote:> I'm doing some rendering and I am finding that there is a huge difference
in
> color between my TFT (laptop) display and my monitor.

> I am working with TBitmaps and L.A.B color space for brightness control
and
> converting back to RGB.

> Is there any solution to getting the colors to look more or less the same
on
> both displays?  Is this the fault of my code or simple brightness and
> contrast adjustments on the displays?

> Stan.

 
 
 

Color difference between Monitor and TFT displays

Post by Stan » Tue, 11 Dec 2001 21:55:07


I don't know what an ICC engine is.  To be honest,  this is the first time
I've tried doing this kind of rendering.  Normally I work with an artwork
package and in Delphi I simply blit pre-prepared images around the place
when required.

Regards

Stan.

 
 
 

Color difference between Monitor and TFT displays

Post by ADS » Tue, 11 Dec 2001 22:27:49


look at www.littlecms.com

it may solve your problem, but to be honnest, monitor have a very poor color
gamut in particulary TFT monitors....

Quote:> I don't know what an ICC engine is.  To be honest,  this is the first time
> I've tried doing this kind of rendering.  Normally I work with an artwork
> package and in Delphi I simply blit pre-prepared images around the place
> when required.

> Regards

> Stan.

 
 
 

Color difference between Monitor and TFT displays

Post by Jens Grusche » Wed, 12 Dec 2001 09:36:47


Quote:> I'm doing some rendering and I am finding that there is a huge difference in
> color between my TFT (laptop) display and my monitor.

When I bought my TFT I also had this problem, but spending some time
adjusting it made the image very similar to my old monitor (note that on
different monitors depending on the settings the colors are different,
too).

The main difference is that on normal monitors the brightness is
generated, on TFTs the darkness is generated (there is a lamp and all
non-white pixels are darkened), so many characteristics are exactly the
opposite. On normal monitors very dark colors are often a problem (no
difference between very dark grays), on TFTs this is true very bright
colors. On normal monitors a gamma value above 1.0 is good in most
cases, on TFTs the gamma value has to be below 1.0 (at least on mine).
If there is no gamma control on the screen, maybe you find it in the
graphics card settings (the GeForce has a gamma control for example).
Changing the brightness and contrast might also help. But this has to be
done by the user, not by the programmer of the software (well, of course
you can include color settings to your software, but if the user has
done it right she might want it that way).

Jens

 
 
 

Color difference between Monitor and TFT displays

Post by Earl F. Glyn » Wed, 12 Dec 2001 10:04:47



> I'm doing some rendering and I am finding that there is a huge difference in
> color between my TFT (laptop) display and my monitor.

> I am working with TBitmaps and L.A.B color space for brightness control and
> converting back to RGB.

> Is there any solution to getting the colors to look more or less the same on
> both displays?  Is this the fault of my code or simple brightness and
> contrast adjustments on the displays?

The color gamuts of various devices can be quite different.  It simply is not possible to display
(or print) the exact same colors if two devices don't share the same color gamut.

A simplistic approach is to view the gamut on a CIE Chromaticity chart.  For your CRT monitor, this
is a "Maxwell triangle" of the three primary colors.  A better approach is to view the gamut as a 3D
convex hull.   See the info and example by Karl Gulyer from Hallmarks about this 3D convex hull
approach under "Gamuts" on this page:
http://homepages.borland.com/efg2lab/Library/Color/Science.htm

Also, look at the "gamut mapping" and "CIE Chromaticity Chart" entries on the same page for other
items related to gamuts.

--
efg -- Earl F. Glynn, Overland Park, KS  USA
efg's Computer Lab Mirror:  http://homepages.borland.com/efg2lab

 
 
 

1. Color difference between laptop screen and external monitor?

I'm using a Sun 17" LCD monitor as an external monitor to my white iBook
laptop running OS 9.2.  Objective is just to have a larger display for
aging eyeballs.  Operates in video mirroring mode (all that's available
with an iBook), 1024 X 768.

Everything works fine, except desktop colors are not as fully saturated
(if that's the right term) -- not nearly as "bright" or "deep" in my
layman's terms -- on the larger terminal as on the laptop screen.  

Example: menu bar, scroll bars, toolbars are all a light to medium blue
on the laptop screen; on the larger monitor they're essentially white.  
Light blue hairlines in certain programs aren't visible on the larger
monitor.

Darker colors look more or less the same to me on either screen (and
color slides and digital fotos actually look equally good to me on
either screen).

Can someone advise me as to what settings or prefs I should start
messing with to get darker colors on the larger monitor.  Color Sync
control panel? -- but what should I do in it?  Or something in the Sun
monitor's menu?

Thanks for any assistance.

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