Please send digital photos of the patient whenever trying to communicate a shade that doesn't perfectly match the shade tab (that would be most of the time). Hold the closest matching shade tab(s) you have on the same plane next to the tooth you want to match. Take a few pictures at different angles and in different light if you can. Finally, include the shade tab # in the picture and make sure it’s in focus.
Just remember that even one bad photo can be better than none at all. Not all cameras will accurately capture the color of a tooth, but they can still communicate a considerable amount of information such as subtle dierences and location of colors. A photo is worth more than any words you could use to describe "a little more translucent than the shade tab" or "a little fluorosis on the incisal".
Although color isn't precisely accurate, pictures provide helpful information to your Oral Arts ceramist to help achieve an acceptable shade match.