Literally any photo you see will be 'impure'; as soon as the image is captured from the sensor, the raw data goes through many, many transformations before it arrives at the final image (white balance, exposure adjustment etc. etc.). I guess we could draw the line at how much post-processing is applied. Having said that, photography is very much an art form, and post-processing is just one of the many steps which goes into creating the intended image.

Film photography also has many variables such as film type and development process - fascinating stuff!