I’m a huge advocate of using products with an SPF. Especially being the pale person that I am! However, have you ever noticed when you have a photo taken your skin looks slightly paler? Some foundations with high spfs have an ingredient in them called Titanium Dioxide. This ingredient *which is especially high in Dior foundations* will react to the flash of a camera and pale you out.
Just be aware of this when you are having your trial. I use a lot of SPF 15 foundations and have found there is no problems with these. This has come from many trials. You need to try out the makeup before the day and be sure to take a photo with a camera (not simply your mobile) to see how it all looks.