[X] My Assistant

[algorithm]

I for one look in wonderment at the work of Damia and others. Being a curious soul I also want to know how they do it and also have a go at colourising myself.
I have searched through Google trying to find tutorials on colourising but the results tend to be in the realms of changing red cars into green cars etc.
I have also searched for colour mapping, gradient mapping...the list goes on!
I have come to the conclusion that I don't know what I am talking about and therefore don't know what question to ask.
Could someone please point me in the direction of a good resource on colourising greyscale images using colours from another 'reference image'. (Is that the right question?)
I have Photoshop cs4, cs4 extended, cs5.1 and cs6.
All this software and no knowledge.....it's getting embarressing!!

[Gerald]

Splitting a color image in hue/saturation/value channels, then combining the grey-scale image as value channel with the hue and saturation channel of the color image could be a starting point.
The image geometries should match.