Extending the colour key
Extending the colour key describes a method devised by Ray Harris, and published by him in the London Philatelist, by which colour can be assessed more objectively than by eye, but which does not require access to a spectrometer.

Measuring cancel diameters accurately
Measuring cancel diameters describes a method for measuring the diameter of even partial cancellations very accurately. It which uses any photo-editing software which includes the facility to use layers allied to a transparency devised by Ray Harris which can be downloaded from the page

Searching a folder of .pdf files
A note from Ray Harris describing how to use Adobe Acrobat to search for a particular word or phrase in all the .pdf files in a particular folder. If you have 100 .pdf files in a folder this can be a very helpful time-saver!