In Easy Media, before generating the ICC profile, you have the option to import a "custom viewing light source" or measure your source using the Xrite i1-Pro 2 with the "ambient light measurement head".
This viewing light source applies to custom "viewing/ambient" light conditions and when using a LED backlit box you're looking for a custom "illuminating" light source. In transmissive, the "viewing" light source is *not* the ambient light, like in reflective, but the illuminating light from behind the image.
So the X-Rite i1-Pro 2 with the "ambient light measurement head" mounted on it, can perform this measurement using EasyMedia (select the spectro icon under the light source selection). Be careful, without this special filter, the measurement of the light will be invalid ... Take note this should be performed with a LED source only and without fluorescent light (or other light sources) that could disturb the measurement.
Don't expect too much when used to measure a transmissive source, as the adaptation used, is only a basic matrix conversion that is very limited and geared towards a reflective source.
Instead try the M0 or M2 measurement condition in the spectro, if - and only if - the light source doesn't have UV, or a very limited amount of UV.
