Movie (cough, "Theatre" mode) on my sony looks great on films. Switch back to normal and the bright stuff gets burned out. But normal mode is fine for other stuff. Luckily, its just 1 button press to switch in and out of Theatre mode.
I would say though that I think most people like their films to have the over bright, burned out appearance.

not saying it doesnt' work for you.
but i'm not going to switch screen modes every time i change from an HD to SD channel, as that would involved picking up two remotes.

clearly that is just silly.

I prefer my movies to look as close to the original as possible, which is why I have my main screens ISF calibrated and only use the user setting. Can't stand images that are too saturated in colour/overly bright or both, it just doesn't look natural - if you are creating a home cinema environment you want it as close to how it looks in the cinema, surely, not where everyone looks like they are on TOWIE.

The viewer has greater control over the image these days, some of the picture settings I have seen look hideous, I really wonder what the hell the user is using as a reference. Before plasma and LCD you just had the basic controls (still too many for some ), unless you were confident enough to go into the service menu, still enough to over adjust settings, but at least the areas that could be adjusted was limited.

i have a mac mini connected (via HDMI) to this TV also, so i might see if i can get some calibration images to calibrate the screen.

however that does really rely on being able to disable all the digital "improvement" settings that the TV has.

If you can locate some colour filters that will help in setting the colour/RGB settings, you will of course need to find/download and run the colour bar test pattern.

There are plenty of other test patterns available for greyscale/brightness/sharpness etc.

You should be able to disable all digital enhancements apart from the auto dimming, hopefully that shouldn't interfere with the test patterns you are running.

There maybe 2 probs if anyone starts calibrating their screen using a pc connected to the TV.

1, today most if not all tv's above portable size will allow for separate colour, bright, contrast, col temp, sharpness, noise reduction, etc etc on each input. So u set it up to make the pc test look right, then switch to a different input maybe a digi box or bluray, or the built in TV tuner, and the settings won't have changed for those. U may need to set up each input manually. A piece of paper for taking the info might be a good idea. However some tv's in the picture calibration menu allow you to make the settings either for just the input your on or "generic/common"- which clearly sets up all inputs and TV tuner mode the same.

2, with my elderly Sony and my new one, the picture options for adjustment offered when viewing a pc input (even though it's using a regular hdmi port) are a bit different compared with adjustments on offer when viewing a traditional input like a digi box, bluray, Etc. This could hinder setting up multiple inputs the same.

Not so silly if you use a one for all remote.

which i don't, as i clearly said.

I've just bought a Samsung UE50JU6800 and this happens to me, envy time credits come on a black background my picture dims.

Anyone know how to switch this off?

Look to see if it has a black corrector or light limiter set on

I've been through all the settings and can't find a way to adjust this, and it's really starting to bug me, it's happening on really dark scenes in programmes making them go darker. I can't believe that something like this is turned on by default

Could be in the advanced settings menu, should be called "Dynamic Contrast", also try changing the "Black Tone" option.

Could be local dimming which can normal be switched off in the service menu, it couid also be Samsungs micro dimming, this can not be turned off, but it has been disabled in Movie picture setting.

How do I get into the service menu?

I wouldn't suggest entering the service menu unless you are very confident in knowing what you are doing, it is nothing like the user menu, it's very easy to completely mess up your TV.

I'd first try the Movie setting first to see if that makes a difference, if it does you should still be able to customise that setting to how you want it, with the offending feature disabled. If it makes no difference I'd double check all user settings before considering entering the service menu or having someone look at it for me.

You don't! It is brand new, contact your dealer, not a forum, if you want something changed in it.

Ok, I've changed it to Movie, but the picture is awful

Gonna take a lot of tinkering to get an acceptable view....

More importantly, has the dimming effect gone?

If it has, then just copy your basic settings across from the setting you were previously using, there maybe a few settings you won't be able to change/greyed out ie. gamma, white balance, all depends how the manufacturer has configured the presets, but these are normally in advanced settings and probably never selected by the average viewer so don't worry to much about them.

Yes it's gone