[Gimp-user] colour to black and white

[norman]

< snip >

> Decompose you image to RGB components.
> In the new image, hide the red and green layers.
> Add a layermask to the blue layer, initialized to a "Grayscale copy of  
> the layer".
> Fill the blue layer with black.
> 
> OPTIONAL: Most orthochromatic film would respond to some extent to  
> green, so repeat the last two steps on the green layer, make it  
> visible, and set its opacity to a relatively low value (0-30%).

This is very interesting and to a learner like me not too complicated.
Perhaps I did not do it quite right but I have what appears to be an
overlay of small black and white squares. How do I get rid of that?
> 
> This method is a bit crude, but should provide something not entirely  
> unsuitable. A more accurate approach would probably entail applying  
> appropriate curves to the different color channels.

Crude or not it looks very effective and a good starting point. Thank
you.

Norman