The spirit photographer William Hope tricked William Crookes with a fake spirit photograph of his wife in 1906. Oliver Lodge revealed there had been obvious signs of double exposure, the picture of Lady Crookes had been copied from a wedding anniversary photograph, however, Crookes was a convinced spiritualist and claimed it was genuine evidence for spirit photography.
It depends how you became a psychic medium; if you had a mentor, they will probably want to keep an eye over you for a while, just till you feel comfortable on your own. Even if you've come to this realization on your own, it can be helpful to get advice and guidance from an experiences psychic. In some cases, your clients might only trust you if you are known to have been mentored or guided by an experienced and known psychic.
Senses used by mental mediums are sometimes defined differently from in other paranormal fields. A medium is said to have psychic abilities but not all psychics function as mediums. The term clairvoyance, for instance, may include seeing spirit and visions instilled by the spirit world. The Parapsychological Association defines "clairvoyance" as information derived directly from an external physical source.