I am noticing that more and more programmes, particularly ones set in the past when there would have been only candlelight, are seeming to want to take realism to ridiculous lengths.

Many scenes are, on our TV at least, basically unwatchable as all you can see through the gloom is occasional movement of the characters. It's hard to see the expressions on their faces which, quite often, would be useful.

I have tried turning the brightness up as far as it will go but it makes next to no difference.

Am I being really thick here? Is there some other adjustment that might help.

It's a sony bravia kd55x8509c if that helps.

Somewhere, probably under advanced picture setting will hopefully be a setting for gamma.
On my Sony the options run from -3 to +3. +3 makes the dark details more visible, but can make the picture on brighter scenes look washed out and pale. Play with it until you find the best balance.
Increasing backlight may help too, but go too high and the screen will be uncomfortably bright at times.
Brightness should be left where it was. Usually the midpoint. Raising it will just make black look grey.
Concentrate on gamma first.

Edit. I think this may be one the Sony sets where backlight is sensibly called brightness, and brightness is called black level. If it is, ignore my paragraphs on them.

It also occurs to me that Advanced contrast enhancer is another setting to play with if all else fails.

I'll think of all the options before posting next time.

The best thing to do is have the TV properly calibrated for the best possible picture either by paying to have it done or buy a calibration disk and do it yourself.

Then at least you'll know the screen is set up as well as it can be and that any problems with not being able to see anything are down to how the programme was shot and lit rather than your telly.

Which picture mode are you using? Using the options button set Scene Select to General, Picture to Standard then in advanced settings set Black Corrector and Advances Contrast Enhancer to Low. Gamma is also available there but I have never needed to use it. If you feel you have messed things up simply select Reset. Alternatively you can jot down the settings in Standard, resetting first if you have altered them, enter them in Custom, then play with them knowing you can easily go back. I have the back light on 5 brightness on 50.

Maybe it's not the TV.

How bright is the room lighting where you watch the TV? For best results in seeing what's going on in dark scenes you should be watching in cinema-like conditions. I.e near total darkness. It helps if you've got dimmable lighting in the room and set it to minimum.

Of course that's not always possible in a family lounge, and brighter content doesn't need it, but they're the ideal viewing conditions.

Pretty sure you'll get better results watching in a dimly lit environment, but you may then notice then how far from true black LCD displays are, especially if you've previously turned the brightness way up in an effort to alleviate the issue.

Thanks very much to all who have answered. Some of this stuff sounds rather "technical" but hopefully will make more sense when I am actually looking at the TV settings menus.

GDK may have a point. The sort of programmes I am talking about (Poldark was the one that prompted this question) do not appeal to my OH so I inevitably watch them on my own during the day as we watch TV together in the evenings (in the near dark as is recommended actually).