Global Dimming
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.
LCD Local Dimming vs CRT Blooming
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.
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.
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.
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.
LCD Local Dimming vs CRT Blooming
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.
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.
- 317 nits on a small white box on a black screen.
- 302 nits on a ANSI contrast white test rectangle (50% APL).
- 1.91 nits on a ANSI contrast black test rectangle.
- 0.12 nits on the bottom of a black background with a large white bar up top.
- 0.01 nits on a black background with only a mouse on screen.
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.