Monochrome abstract of the River Ness

As far as I understand it to ’abstract’ is to remove a layer of information from something like a photograph, in this case the colour. (Colour is like sugar, highly attractive to the brain.)  A colour photo in itself is also an abstraction from reality because you have selected some visual information and ignored the rest.
     One of the reasons monochrome photos work is that because colour tends to overrun the senses, and if it is removed, your brain zones in on the tonal variations in the picture. That’s it.