That sounds more like poor lighting and makeup to me, and is the reason why I would do a setup performance if I were doing something that would end up on a banner that big. The actors can still act the same, but you need full control of the lighting to get the best results, using HDR is just a bit of a bodge really and by setting the lighting for the camera rather than the audience for a one off performance not for public eyes would give you far better results.

I''l say this first before I say what I am about to say as I don't know your photography at all, so I am not talking about you here. I hear it all the time here in the UK "I shoot weddings in a photo-journalist style" when what they really should be saying is "I have no idea how to light stuff so I just snap what is there". Of course there is an art to using available light, but it far more rewarding when you yourself have crafted the whole image.

Whilst it can be true you get better reactions when people are largely unaware they are being photographed I think the benefits of lighting things properly out weigh that.

There is also an added benefit, if things are lit properly it doesn't matter what camera you use, it will always look good

Cheers

Cris