Slider for dithering

[Dodgy]

Hiya,

I would like to ask for a slider to control the amount of dithering used in batch conversion from rgb>8bit. At the moment for the pictures I'm converting, no dithering is not enough, whilst dither on is too much dithering. There must be algorithms which allow a control over the amount of dithering, as I used to use them back in the old amiga days.

Thanks.