Image parameters contd.
Adjusting the tone alters the shape of the 'S curve' used to map the linear image data captured by the sensor into the correct gamma. A lower contrast setting maintains more of the original data's dynamic range but leads to a flatter looking image. A higher contrast setting stretches the grayscale (dark to light) of the image and could lead to clipping of both shadow detail and highlights. Sony provides 7 settings in total (though as the images below show, the actual range of the contrast control isn't huge).
Adjusting the brightness appears to shift the mapping of the 'black point' which could be useful for 'lifting' shadows on a bright day or delivering a more definite black in a studio situation.
The zone adjustment enables you to perform zone matching which effectively stretches or compresses the shadow or highlight areas of the grayscale. Use a negative setting to lift shadows for low-key shots or a positive setting to compress (and maintain) highlights for high-key shots. You can see this in effect in the histograms below.