Archived posting to the Leica Users Group, 2005/07/20

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Subject: [Leica] Some Comments on LCD technologies
From: tlianza at sequelimaging.com (tlianza)
Date: Wed Jul 20 06:36:04 2005
References: <200507200313.j6K3BoeG049673@server1.waverley.reid.org>

Hi to all,

I noticed some requests for information about LCD panels and I thought that 
I would share some of my experience with the group.  I've been designing 
calibration systems for displays for over 17 years and I have a great deal 
of direct interaction with some of the best display manufacturers and their 
technology.  My team designed the Sony Artisan hardware as well as many 
other calibrators that are shipped with displays.  We also designed the 
Eyeone Display for Gretagmacbeth.

When you are looking for an LCD panel for critical image viewing, you have 
to expect to pay a premium for it.  If you are looking at quality panels you 
should be aware of a few acronyms that are hints about the panel quality and 
usability for typical image viewing.  Panels that use IPS (typically Apple, 
NEC-MITS high end panels), VPA (Samsung), SHA (High end sharp panels) 
provide excellent field of view and great stability.  To the best of my 
knowledge, all the high end Eizo panels utilize IPS technology. A data sheet 
will typically list the technology as TFT/IPS or TFT/VPA.  If you only see 
TFT, it's a good bet that you are not getting a panel that has high image 
quality potential.

I personally use a Samsung SyncMaster 243T.  This is a state of the art 
panel, but it cost about $1800 dollars. It is a 24 inch, VPA technology 
panel with a resolution of something around 1900X1200 pixels.  If you go to 
the Dell website and search for 24 inch panels you will find this one and a 
cheaper one.  The cheaper one has a higher luminance and actually has a 
faster response time.  The point is that it is a standard TFT panel and it's 
angular field of view, while large, changes rather dramatically, making it 
useless for image evaluation activities.  That's why the luminance is 
higher, it is the difference between looking into a search light verses 
looking at a more diffuse surface.  The higher quality panels have longer 
response times, meaning that they are not really well suited to viewing 
movies or gaming.  This response time is result of the switching mechanisms 
in the panel.  That is a fundamental tradeoff in the industry today, fast 
response and high on-axis luminance vs a wide field of view and good tone 
reproduction.

The higher luminance of the LCD can be problematic.  My LCD luminance is a 
factor of three times greater than my CRT.  I can't have them both on the 
desk at the same time.  When used in dim lighting, it can be quite tiring. 
For this reason, if you are planning to switch to one of these newer LCD's 
you will have to pay a bit more attention to your surround environment, if 
you are doing critical color evaluation.  This has been the biggest problem 
in my workspace. The large surface of the panel is good when working in 
photoshop because I set the surround to a neutral on the panel (Full screen 
display).

I have not found color gamut to be a problem.  As a color scientist, I'm 
well aware of the issue and in my imaging workflow, it's not a problem.  If 
you are working in Graphic Arts reproduction activities, it may be a 
problem. The high absolute luminance causes an observer to see the scene as 
more saturated and slightly more contrasty than at lower luminance.  The 
tone reproduction of these modern displays is quite good.  The higher end 
displays have much better control of the driving circuits and the display 
transfer functions are very close to gamma - law relationships.  Cheaper 
displays tend to have saturation issues in both the highlights and the 
shadows.  I designed a rather critical digital test target for displays and 
I can say that in both shadow and highlight, the high end LCD displays often 
perform FAR better than any CRT monitor that I have used.  I have a Sony 
Artisan and it is now sitting in storage.  Once I started using this Samsung 
flat panel, the rest of the image quality issues such as noise, flicker and 
sharpness just overwhelmed any small contrast ratio issues the monitor might 
have .  The fact is that this panel has a 500:1 contrast ratio which 
requires no tedious bias adjustment.

I have to make a note about calibration.  Calibration of the low end TFT 
panels is very tough.  You can't really correct for many panel defects 
through calibration. When I calibrate the panel on my PowerBook 15", it 
corrects the highlight saturation , shadow clipping, and generates the 
correct white point, but at the expense of display luminance and I'm still 
faced with a display that has limited viewing angle.  If you are a Leica 
user you should take the time to test some high end LCD displays from 
companies like Eizo, Sony, NEC, Mits, Samsung and Lacie.  I would avoid the 
19inch formats because there is a lot of cheap technology in expensive 
cases... Stick to 20 inches and above and look closely at those specs. Bring 
a cd with some images to a store and view the images.  Unfortunately, you 
are not going to see many of the high end displays at Best buy or Circuit 
City.  You will see them at PMA and CES and other tradeshows.

Take care and take good pictures !

Tom Lianza
Director of Display and Capture Technologies
GretagMacbeth LLC
3 Industrial Drive
Unit 7&8
Windham, NH 03087
603.681.0315 x232 Tel
603.681.0316 Fax



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