Documentation update

doc/readme.md

@@ -265,13 +265,11 @@ reduce attribute artifact edges.
 
 #### Colour Distance Algorithm
 When making a decision on which Spectrum colours best match those of the source 
-image's pixels a colour space "distance" is evaluated.
+image's pixels an RGB colour space "distance" is evaluated.
 The choice of algorithm for this evaluation is configured here - typically
-the Compuphase algorithm is the best and uses heuristics based on human vision,
+the Luminance or Compuphase algorithms perform the best and use heuristics based on human vision,
 the classic Image to ZX Spec algorithm next (which is just a simple sum of RGB space distances), 
-followed by the Euclidean which is the straight line distance in RGB space. You may find
-any one of these better suits your use case, typically the latter two are interchangeable however
-classic tends to occasionally favour darker colours which can lead to better results.
+followed by the Euclidean which is the straight line distance in RGB space.
 
 #### Video Import Engine
 By default Image to ZX Spec's uses HumbleVideo which is fast platform native video