As far as the fluctuating contrast/blacks are concerned, there actually seem to be three dfferent "dynamic effects" at work. The three effects are: 1) floating black levels, 2) contrast/gamma correction or palette optimization, and 3) contrast clamping.
1. FLOATING BLACK LEVELS
The floating black levels are most noticeable when trying to watch the display with very low or no surrounding illumination. So first rule is to use adequate background illumination when watching the display particularly at night.
The flotation of the blacks is a little more pronounced in the Day-Dynamic mode than in the Day-Normal and Night modes. However, you may find the add'l contrast enhancement of the Day-Dynamic mode beneficial when trying to view darker films, because it will elevate shadow information so it's easier to see and looks more dynamic. So I wouldn't necessarily rule it out. Just be aware if you're seeing a noticeable drop in the black levels when the screen goes completely or nearly all black with the Day-Dynamic mode, that that can probably be made less dramatic/noticeable by going to either the Day-Normal or Night modes.
2. CONTRAST/GAMMA CORRECTION OR PALETTE OPTIMIZATION
I'm being deliberately vague about exactly what to call this effect to cover my ass, since I'm not sure exactly what the correct term for this is.
This effect is much more noticeable when using the Dynamic Contrast Mode
(which is a different setting btw than the Day-Dynamic Day/Night mode, and located further down in the video menu). So first rule is set the Contrast Mode to Normal rather than Dynamic
. Do this for all three Day/Night modes, to insure that it doesn't accidentally creep back on, when switching between them, as delphi96 and remotecontrolled mentioned several posts ago.
Rule #2 for this effect is to avoid contrast/palette correction hot spots in the Contrast control
. As mentioned here
and elsewhere by others, there seem to be "hot spots" in the Contrast adjustment, where the display is particularly prone to making noticeable contrast/gamma corrections.
On my 42HDS69, those "hot zones" appear to be at ~33% Contrast for the Day-Normal and Night modes, and at ~19% and ~60% in the Day-Dynamic mode (for my component 480p input). It may vary depending on the display, input or content though. So don't just go by my numbers, check it out on your own display.
An easy way to find these hot spots is to pause on a frame that has a fair amount of dark detail, and then step the Contrast up and down until you find the setting (or settings) where the darker tones in the picture make an abrupt change in brightness. Setting Contrast at that level or very close to it seems to create much more noticeable contrast fluctuations in the picture.
If you obey the two rules above (ie set the Contrast Mode to Normal rather than Dynamic, and avoid hot spots in the Contrast control), I think there should be little or no contrast correction visible with normal viewing. (I see none on my TV.)
3. CONTRAST CLAMPING
As mentioned here
, the 42HDS69 also has a contrast clamping feature, which is designed to keep scenes with a high average picture level (APL) from becoming too overpowering to your eyes. This can be a useful feature to have on some displays with less than perfect contrast ratios and black levels (if you don't abuse it), because it can permit you to set contrast a little
bit higher than perhaps you normally would to improve the look of darker scenes, and the display will automatically "clamp down" on brighter scenes so they're not as stressful on your eyes. (I still would not advise setting contrast any higher than what's comfortable for your eyes given the surrounding illumination in your viewing area though.)
This feature should operate more or less transparently, so you generally shouldn't notice the clamping effects in normal viewing. However, just so you know (and might guess from above), the clamping is "weakest" at low contrast settings, and "strongest" at high contrast settings. What I mean by strong and weak is that the clamping will go into effect on darker and darker images the higher Contrast is set. To give an idea what I mean, here are the clamp points for DVE patterns of varying brightness (APL) using the Night mode on my own TV with a component DVD player (with a 0 IRE black level).
40% APL clamped at ~60% Contrast (DVE Chapter 14, Title 3)
60% APL clamped at ~20% Contrast (DVE Chapter 14, Title 4)
80% APL clamped at ~9% Contrast (DVE Chapter 14, Title 5)
100% APL clamped at ~9% Contrast (DVE Chapter 14, Title 6)
This is with the Brightness control adjusted close to DVE spec. Since the clamping is dependent on APL, the clamp points will likely change depending on how other controls (e.g. Brightness, Black Enhancement, Day/Night and Contrast Mode) are set on the display, and depending on the black level of and possibly other characteristics of the source. (See this subsequent post #206
The only time I notice the changes in picture intensity due to the clamping on the 42HDS69 is when looking at stills and other patterns on my PC, and patterns in DVE. The clamping is so quick in normal video viewing, that it just seems to come and go more or less invisibly.
If for some strange reason you do begin to notice the clamping at higher Contrast settings, then you might try reducing Contrast (and possibly also your surrounding illumination a little) to see if that helps. Or possibly change to a different Day/Night mode. Generally speaking though I'd say this is a feature which can simply be ignored and left to go about it's business as usual.
Contrast/white level clamping is different than "crushed" or "clipped" whites btw. There appears to be no crushing or clipping of whites on the TV.
If I discover any more tricks on this stuff, I'll be sure to pass them along (and hope others will continue to as well), however, since implementing the above, I've seen virtually no perceptible flickering, or fluctuations of contrast in the picture on my TV during normal viewing.
The only effect that's occasionally noticeable to me is the floating of blacks (primarily with the Day-Dynamic mode) when the screen goes nearly or completely dark.
My main beef with the 42HDS69 is that it seems to be suited for use with brighter surroundings than I prefer for my usual nighttime viewing. The black levels are generally too high and the range of contrast adjustment seems a bit higher than I need. That's why I'm thinkin that maybe a different brand or model might perhaps be a better a fit for me. I know that the phosphors will gradually begin to fade over time as well though, so that's another thing I'm trying to factor in too.
This is the first plasma I've tried however. And there are alot of things I like about this TV, so whichever way I go, I suspect I'll probably always have a little soft spot for the ALiS 42HDS69's.