Most prints are intended to be displayed using light that illuminates the front of the image. If the material printed is to be lit from behind, with light shining through the image, a transmissive profile will provide a more accurate rendering of the image. Consider a transmissive profile if you are printing onto transparent or semi-transparent film that will be back-lit. The normal, "reflective" type profile will not normally capture the effect of light passing through a semi-clear media. Especially for film that is less opaque, the effect of a light source transmitting through the semi-clear media and through the ink can best be captured using a spectrophotometer that is specially made for this purpose. These kinds of measurement devices are not common.