Lumen prints (also known as "sun prints") come about when a subject is arranged on black and white photo paper in the dark, then placed outdoors in the daylight for hours. Color are not brought about by Photoshop processiong; they spontaneously appear, depending on an unpredictable list of factors, including geographical location and time of year and these images are true to what the process produced.

Please take this link to view a Photographers Formulary Newsletter featuring Diane Kaye's Lumen printing:

https://www.dropbox.com/s/olkywfd2c73tgsp/Diane%20Kaye%20-%20LUMEN%20Article%204-15-14.pdf?dl=0