High Acutance developers give increased sharpness and more defined grain structure – that is to say, the trade off for sharpness is more visible grain. This can be seen as desirable or undesirable depending on your particular objectives and the look you want to give to your finished images. High Acutance developers, as a general rule, are most suited to slower speed films such as ISO100 / 125 and below, but this is not a rule cast in stone (as always in black and white!). One of the best known High Acutance developers was Agfa Rodinal. After the demise of Agfa in 2005, Tetenal is now making this developer as “Paranol” to the exact formula.