I have had the opportunity to meet men and women working in the sex trade in my travels to Mexico's northern and southern borders.

My intention has been to encourage viewers to face their prejudices about prostitution, sex and aging while reflecting on the complex and varied forms that love and loneliness can take.

Of all the subjects I have photographed, the most controversial and the one that has moved me the most has to be the prostitutes who are getting on in years. They are true survivors.

I have had the opportunity to meet men and women working in the sex trade in my travels to Mexico's northern and southern borders.

I have been exploring [Mexico City's] La Merced, [a public market famous for prostitution,] on and off for the last 23 years. The prostitutes and their world have been the main subjects of my photographs.

"Plaza de la Soledad" is a documentary about Carmen, Lety, Raquel and Esther, four strong women - middle-aged and older - who want to break a vicious circle that began with abuse and abandonment suffered from an early age. They simply want to have a better life. The film follows their quest to find true love and their capacity to transform themselves.

My biggest challenge was moving from photography to film without losing my way of working - which is very intimate and learning to collaborate with more people, since photography for me is a very solitary process.