This has been an extremely interesting exercise and i can´t help but recommend it to everyone, you´ll learn a lot!
The thing that most amazed me is the fact that the original portraits have a very limited gamut and they achieve a wide amount of colours just by desaturating them. For example, parts of the dress of the woman and their eyes doesn´t have a trace of blue at all. It´s just a very desaturated brownish tone.
I´ve tried to use the same technique and i think i´ve achieved somewhat similar results. This would be very, very useful in future paintings.
The original portraits are:
Self portrait 1636-38 - by Rembrandt.
Maud Glen Coats, Duchess of Wellington - by John Singer Sargent.
