mirror of
https://github.com/gomson/TimothyLottes.github.io.git
synced 2026-08-04 14:48:49 +00:00
57 lines
2.7 KiB
HTML
57 lines
2.7 KiB
HTML
<html><head><link rel="stylesheet" href="style.css"></head><body><div class="page">
|
|
<h1>20160126 - Local/Global Dimming, Blooming, Contrast Ratios - CRT/LCD/Plasma/OLED</h1>
|
|
<br>
|
|
|
|
<b>Global Dimming</b>
|
|
<br>
|
|
OLED HDTVs drop to about 33% of peak brightness on a full white screen.
|
|
My Samsung Plasma HDTV has similar issues.
|
|
The random made-in-1996 CRT I just profiled at home drops to about 60% of peak brightness on a full white screen.
|
|
Global dimming has been around for a long time.
|
|
<br>
|
|
<br>
|
|
<b>LCD Local Dimming vs CRT Blooming</b>
|
|
<br>
|
|
LCD TVs often have LED back-lights split into zones (on the order of dozens for poor quality and low hundreds for better quality),
|
|
with individual control of the brightness per zone.
|
|
This zone brightness control simultaneously moves up or down the {black level, peak brightness} as a joined pair.
|
|
A single-pixel thickness peak brightness line on a black background
|
|
forces black level high in a blooming pattern of where the line intersects zones.
|
|
For this reason I always turn off local dimming if it is an option on a LCD TV display.
|
|
ANSI contrasts can still reach 4000:1 with the best LCD panels without any local dimming.
|
|
<br>
|
|
<br>
|
|
CRTs in contrast have local blooming (talking about the large diffuse effect, not the shadow-mask-scale effect).
|
|
Lets look at some measured numbers from my Sony Wega CRT TV,
|
|
with ANSI contrast being the standard 4x4 rectangle checkerboard pattern of black and white boxes.
|
|
<br>
|
|
<br>
|
|
<ul>
|
|
<li>317 nits on a small white box on a black screen.</li>
|
|
<li>302 nits on a ANSI contrast white test rectangle (50% APL).</li>
|
|
<li>1.91 nits on a ANSI contrast black test rectangle.</li>
|
|
<li>0.12 nits on the bottom of a black background with a large white bar up top.</li>
|
|
<li>0.01 nits on a black background with only a mouse on screen.</li>
|
|
</ul>
|
|
<br>
|
|
ANSI contrast ratio for this Wega is a poor 158:1 (my random 1996 CRT gets 265:1 in comparison).
|
|
And if one stops here and compares to the great LCD, the LCD has over 4 extra stops of dynamic range?
|
|
But this isn't the full story.
|
|
For the Wega as Average Picture Level (APL) drops from 50% with ANSI contrast test,
|
|
to something more natural to look at, contrast ratio improves.
|
|
Seeing 2500:1 for black with the large white bar case,
|
|
and then almost up to 32000:1 measuring a black screen with only a white mouse away from the sensor.
|
|
And all these tests done in a room at night lit by a few bright lamps.
|
|
<br>
|
|
<br>
|
|
The CRT does not suffer from the LCD local dimming problem,
|
|
a single pixel line won't cause blooming as it does not add enough energy (APL stays low).
|
|
The CRTs blooming looks totally natural in comparison.
|
|
|
|
|
|
|
|
|
|
</div></body></html>
|
|
|
|
|