It seems to me that the difference between the two relates to what is included or what is excluded. Framing refers to the overall photograph, what is included in the photograph and how it is composed within a frame. The frame defines the boundaries of the photograph. Cropping may refer to the post production processes where parts of the photograph are cut thus excluding areas of the original which are not required. However, cropping can also relate to photographs where there is no defined boundary, for example in the photographic collection “Equivalents” by Alfred Stieglitz. In these photographs there is no border or frame and the images appear cropped.