Sarah was born in 1812, the eldest of the Ferneley children, and inherited her father's artistic talent and her mother's beauty. With her lively wit and charm she was the life and soul of her father's studio and shared his love of horses. After the death of her mother in 1836 she took on the difficult task of bringing up her little brother and sisters. Two years later, rather against her father's will, she married Henry Johnson, the portrait painter, and left John Ferneley to cope with his house, studio and family. Johnson died in 1850, and Sarah returned to look after her father, and after his death she remained at Elgin Lodge until her death in 1903. Sarah was a competent artist in her own right, and engraved many of her father's works. She was a leading figure later in life of a circle of fellow artists who met frequently at each other's houses to discuss painting.