You will notice first of all that this is a cropped composition, that is elements of other figures are only partially displayed. It was not common to use this approach during the Renaissance in such an abrupt way and this makes it easy to draw the conclusion that actually this is a fragment of a larger painting. Further research then uncovers other parts to the larger scene and together they help us to construct the overall piece, as it was.
This particular section of what is left has been stored at the National Gallery since around 1860 and much research has been completed in order to understand more about its role in the original artwork. Magdalen herself is identified by the small bottle of ointment that is placed just below her on the canvas, right in the foreground. Christianity tended to use this symbolism within art to symbolise her presence.
One of the procedures carried out on this painting during its time at the National Gallery has helped to reveal more of the background than had been seen for many centuries. A cover of paint, added later, was slowly removed to reveal the original detail used by the artist. Even famous paintings such as this can be subject to amendments by owners in later years who believed at the time that they were protecting or improving the work, but art historians will always endeavour to return any artwork to its original design.